WO2019016798A1

WO2019016798A1 - Processes and devices for gilding gold alloys

Info

Publication number: WO2019016798A1
Application number: PCT/IL2018/050781
Authority: WO
Inventors: Basila KATTOUF; Mario ABBOUD
Original assignee: Nanofine Technologies Ltd.
Priority date: 2017-07-17
Filing date: 2018-07-16
Publication date: 2019-01-24

Abstract

The present invention provides process and apparatus for producing a thin layer of high purity gold on an object made of gold alloy, such as a jewelry item. The process comprises heating a gold alloy having an outer surface to a temperature of at least 150 deg. C. and immersing said gold alloy in a fluidized solid composition comprising at least one salt. The apparatus comprises a heating unit comprising a heating unit internal shaft, which is configured to generate a temperature of at least 150 deg. C; a fluidized bed reactor comprising a freeboard and a fluidized bed internal shaft; and a leverage unit comprising an elongated transport member which is configured to be driven into the heating unit internal shaft and into the fluidized bed internal shaft.

Description

PROCESSES AND DEVICES FOR GILDING GOLD ALLOYS

The present invention provides processes and apparatus for providing a thin layer of high purity gold on objects made of gold alloys, such as jewelry items.

BACKGROUND OF THE INVENTION

Gold, in its pure form (24K) is soft and thus for various applications including the preparation of jewelry, it is alloyed with base metals, such as, copper, silver and zinc. The alloys usually present improved hardness and altered ductility, different melting point and color, among other properties, relative to pure gold. Alloys with lower karat rating, typically 22K, 18K, 14K, 10K or 9K and lower, contain increasing percentages of base metals. The incorporation of base metals in gold alloys results in a hue that is different from the hue/color of pure gold. Typically, in order to restore the coveted golden character, gold jewelry items are routinely electroplated with a fine layer containing higher gold content than the jewelry item, also termed "gilding", resulting in a visual appearance, which is similar to pure gold or to a higher gold content than the initial item.

Another technique of gilding gold alloys, relatively old-fashioned and less popular than electroplating, is depletion gilding. This technique includes immersing a gold alloy, e.g. a gold ring, in an etchant, typically nitric acid, which reacts with the base metals on the surface of the alloy and then removed together with dissolved cations of the base metals, leaving the surface enriched with gold (Grimwade, 1999, Gold Technology 26: 16-23 and Lechtman, 1971 In: Science and Archaeology, MIT Press, Cambridge, Mass. USA; pp. 2-30).

Ding et al. (Advanced Materials, 2004, 16(21):1897-1900), describes the production of nanoporous gold membranes by dealloying a commercially available white-gold leaf. The authors assert that dealloying is historically connected to depletion gilding.

EP 3067220 and EP3067150 describe methods for decorating a timepiece, and refer to optional application of physical vapor deposition (PVD) in the depletion gilding technique.

There still remains a need for improved, low cost, technologies for effectively gilding gold alloys. SUMMARY OF THE INVENTION

The present invention provides apparatus, processes and methods for gold enrichment of an outer surface of gold alloys. Gold enrichment of an outer surface, also termed gilding, is achieved using a variation of depletion gilding whereby the gold alloy is contacted with chemically active (corrosive) composition(s), which selectively remove(s) alloying metals other than gold, from the outer surface. The process disclosed herein involves fluidized bed technique, such that the corrosive composition which is inherently solid, is in a fluid form when contacting the alloy. The selective removal of the alloying metals is accomplished through a chemical reaction, under certain thermal conditions, between the base metals in the surface of the alloy and the corrosive composition. Surprisingly, the apparatus and processes disclosed herein result with unexpected effective coverage of the alloy with the corrosive composition, and a uniformly gilded outer layer. Advantageously, the appearance of the gold alloys dealloyed by the process and apparatus disclosed herein is closer to that of pure gold compared to their original appearance. For example, a 9K alloy dealloyed by the methods and apparatus disclosed herein, may appear as a 18K gold alloy. Similarly, a 21K alloy, dealloyed as disclosed herein would have an appearance similar to that of 24K pure gold.

In some embodiments, there is provided a process for dealloying a gold alloy, the process comprising: heating a gold alloy having an outer surface to a first temperature of at least 150°C for a first time period; and immersing said gold alloy in a fluidized solid composition comprising at least one salt.

In some embodiments, the step of heating the gold alloy for the first time period precedes the step of immersing said gold alloy in a fluidized solid composition.

In some embodiments, the process further comprises heating said gold alloy to a second temperature of at least 150°C, for a second time period, following the immersing.

In some embodiments, the process further comprises washing the gold alloy following said immersing.

In some embodiments, the gold alloy comprises between 20% to 98% gold and at least one base metal.

In some embodiments, the at least one base metal comprises any one or more of silver, copper and zinc.

In some embodiments, the fluidized solid composition comprises a plurality of salts. In some embodiments, the fluidized solid composition comprises two salts.

In some embodiments, the fluidized solid composition comprises at least one salt having a pKa below 11.

In some embodiments, the fluidized solid composition comprises at least one salt comprising nitrate (NO₃ ) or sulfate (SO₄ ^"2) ions.

In some embodiments, the process further comprises providing a solid composition comprising the at least one salt and fluidizing said solid composition in a fluidized bed reactor, thereby obtaining the fluidized solid composition.

In some embodiments, the steps of heating and immersing occur simultaneously. In some embodiments, the step of heating occurs prior to, and during, the step of immersing.

In some embodiments, the outer surface comprises, prior to said immersing, a first amount of the at least one base metal, and wherein following said immersing said outer surface comprises less than 80% of said first amount.

In some embodiments, the heating is carried out for a period of time within the range of 1 second to 120 minutes.

In some embodiments, there is provided a dealloying apparatus, comprising: a heating unit comprising an internal shaft having a proximal opening and a distal opening, said heating unit is configured to generate a temperature of at least 150°C, a fluidized bed reactor comprising a freeboard and an internal shaft having at least a proximal opening, said proximal opening is facing the distal opening of the internal shaft of the heating unit, and a leverage unit comprising an elongated transport member, said leverage unit is configured to drive the elongated transport member through the proximal opening of the heating unit along the internal shaft of the heating unit and through the proximal opening of the fluidized bed reactor and along the internal shaft thereof.

In some embodiments, the elongated transport member is formed as a rod.

In some embodiments, the elongated transport member further comprises a placement section configured to accommodate an article holder.

In some embodiments, the fluidized bed reactor further comprises a gas distribution unit configured to distribute gas flowing therethrough. In some embodiments, the fiuidized bed reactor further comprises a mesh sieve and a distributor, wherein the distributor is flexible, soft and comprises a plurality of apertures.

In some embodiments, the gas distribution unit comprises an inlet tube fitting, and at least one nozzle body connected to a nozzle head, wherein the nozzle head comprises at least one outlet orifice, and wherein the inlet tube fitting is configured to allow gas flow into the gas distributor unit, through the at least one nozzle body, towards the at least one orifice of the nozzle head thereof.

In some embodiments, the gas distribution unit comprises at least one nozzle, the at least one outer distribution tube and at least one inner distribution tube having at least one outlet orifice.

In some embodiments, the apparatus further comprises at least one heat sensor attached to the elongated transport member.

In some embodiments, the fiuidized bed reactor further comprises a fiuidized composition level sensor.

In some embodiments, the apparatus further comprises a camera.

In some embodiments, the fiuidized bed reactor further comprises a fiuidized composition consumption sensor.

In some embodiments, the heating unit further comprises a first plate closure facing the lower opening of the heating unit and configured to be displaced between a close state and an open state.

In some embodiments, the heating unit further comprises a first plate closure and a second plate closure facing the lower opening of the heating unit and configured to be displaced between a close state and an open state.

In some embodiments, the apparatus further comprises a microcontroller configured to control at least one operation of any one or more of the leverage unit, the heating unit and the fiuidized bed reactor.

In some embodiments, the apparatus further comprises a washing unit.

Further embodiments, features, advantages and the full scope of applicability of the present invention will become apparent from the detailed description and drawings given hereinafter. However, it should be understood that the detailed description, while indicating preferred embodiments, of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1A constitutes a view in perspective of a dealloying apparatus having a fluidized bed reactor located beneath a heating unit, according to some embodiments.

Figure IB constitutes a view in perspective of a dealloying apparatus with a fluidized bed reactor offset from the heating unit, according to some embodiments.

Figure 1C constitutes a side view of a dealloying apparatus, according to some embodiments.

Figure ID constitutes a front view of a dealloying apparatus, according to some embodiments.

Figure 2A constitutes a view in perspective of a heating unit from a top-side angle, according to some embodiments.

Figure 2B constitutes a view in perspective of a heating unit from a bottom-side angle, according to some embodiments.

Figure 2C constitutes a bottom view of a heating unit, according to some embodiments.

Figure 3A constitutes a view in perspective of a heating unit with plate closures in a close state, according to some embodiments.

Figure 3B constitutes a view in perspective of a heating unit with plate closures in an open state, according to some embodiments.

Figure 4A constitutes an exploded view in perspective of a fluidized bed reactor, from a top-side angle, according to some embodiments.

Figure 4B constitutes an exploded cross-sectional view in perspective, from top-side angle, of fluidized bed reactor, according to some embodiments.

Figure 4C constitutes an exploded view in perspective of a fluidized bed reactor, from a bottom-side angle, according to some embodiments.

Figure 5A constitutes a view in perspective of a plenum chamber, according to some embodiments.

Figure 5B constitutes a cross-sectional view in perspective of a plenum chamber, according to some embodiments.

Figure 6A constitutes a view in perspective of a fluidized bed reactor in an assembled form, according to some embodiments.

Figure 6B constitutes a cross-sectional view of a fluidized bed reactor in an assembled form, according to some embodiments.

Figure 7A constitutes a cross-sectional view of a fluidized bed reactor in an assembled form, according to some embodiments.

Figure 7B constitutes a view in perspective of a fluidized bed reactor in an assembled form, according to some embodiments.

Figure 7C constitutes a partial cross-sectional view of a bottom portion of a fluidized bed reactor, according to some embodiments.

Figure 8A constitutes a view in perspective of a freeboard flange with a powder base plate and a gas distribution unit, from a top-side angle, according to some embodiments.

Figure 8B constitutes a view in perspective of a freeboard flange with a powder base plate and a gas distribution unit, from a bottom-side angle, in some embodiments.

Figure 8C constitutes a view in perspective of a powder base plate with a gas distribution unit, according to some embodiments.

Figure 9 constitutes a partial cross-sectional view of a bottom section of a fluidized bed reactor, according to some embodiments.

Figure 10A constitutes a view in perspective of a nozzle, according to some embodiments.

Figure 10B constitutes a cross-sectional view of a nozzle, according to some embodiments.

Figure IOC constitutes a view in perspective of a nozzle, according to some embodiments.

Figure 10D constitutes a cross-sectional view of a nozzle, according to some embodiments. Figure 11A constitutes a view in perspective of a powder base plate, according to some embodiments.

Figure 11B constitutes a view in perspective of a powder base plate, according to some embodiments.

Figure 12A constitutes a view in perspective of a fluidized bed reactor, according to some embodiments.

Figure 12B constitutes an exploded view in perspective of a fluidized bed reactor, according to some embodiments.

Figure 12C constitutes a cross-sectional view in perspective taken on line 12C-12C of Figure 12 A.

Figure 12D constitutes a cross-sectional view in perspective taken on line 12D-12D of Figure 12 A.

Figure 12E constitutes a bottom view of an inner distribution tube, according to some embodiments.

Figure 12F constitutes a cross-sectional view of an inner distribution tube, according to some embodiments.

Figure 12G constitutes a zoomed-in cross-sectional view of a portions of the fluidized bed reactor depicted in Figure 12D.

Figure 13A constitutes a view in perspective of an article holder prior to placement on a placement section of a main rod, according to some embodiments.

Figure 13B constitutes a view in perspective of an article holder placed on a placement section of a main rod, according to some embodiments.

Figure 14A constitutes a view in perspective of a dealloying apparatus with a washing unit offset from the heating unit, according to some embodiments.

Figure 14B constitutes a view in perspective of a dealloying apparatus with a washing unit located beneath a heating unit, according to some embodiments.

Figure 15 constitutes a cross-sectional view in perspective of a dealloying apparatus with a washing unit, according to some embodiments.

Figure 16 constitutes a partial view in perspective of a washing unit adjacent to a fluidized bed reactor while articles are placed therein, according to some embodiments.

Figure 17A constitutes a partial front-view of a dealloying apparatus, during phase I of a depletion gilding method, according to some embodiments.

Figure 17B constitutes a partial front- view of a dealloying apparatus, during phase II of a depletion gilding method, according to some embodiments.

Figure 17C constitutes a partial view in perspective of a dealloying apparatus, during phase III of a depletion gilding method, according to some embodiments.

Figure 17D constitutes a partial front-view of a dealloying apparatus, during phase IV of a depletion gilding method, according to some embodiments.

Figure 17E constitutes a partial front- view of a dealloying apparatus, during phase V of a depletion gilding method, according to some embodiments.

Figure 17F constitutes a partial front-view of a dealloying apparatus, during phase VI of a depletion gilding method, according to some embodiments.

Figure 18 constitutes a block diagram of functional components a dealloying apparatus, according to some embodiments.

Figure 19 constitutes a graph depicting colors in a* and b* scale for a 24k gold, a 21k gold alloy before gilding, and three 21k gold alloys after gilding.

Figure 20 constitutes a graph depicting colors in a* and b* scale for a 24k gold, a 18k gold alloy before gilding, and four 18k gold alloys after gilding.

Figure 21 constitutes a graph depicting colors in a* and b* scale for a 24k gold, a 14k gold alloy before gilding, and three 14k gold alloys after gilding.

Figure 22 constitutes a graph depicting change in color vs. abrasion time for a gold- electroplated alloy (squares) and a gold alloy gilded through depletion gilding (circles).

Figures 23A-23F are photographs of a 14K non-gilded alloy (Figure 23 A); an electroplated 14K alloy (Figure 23B); a depletion-gilded 14K alloy (Figure 23C); a 18K non- gilded alloy (Figure 23D); an electroplated 18K alloy (Figure 23E); and a depletion-gilded 18K alloy (Figure 23F) following exposure to ammonium sulfide environment.

Figures 24A-24C constitute graphs depicting changes in gold proportion (Figure 24 A); copper proportion (Figure 24B); and silver proportion (Figure 24C) in a gilded coin as a function of sputtering cycle. Figure 25 is a photograph of an untreated standard 18K bullion coin (#1) and four similar coins after undergoing depletion gilding (#2-5), according to some embodiments.

Figures 26A-26D constitute graphs depicting changes in gold percentage (Figure 26A); copper percentage (Figure 26B); zinc percentage (Figure 26C) and silver percentage (Figure 26D) in a gilded 9K alloy as a function of sputtering cycle.

Figure 27 is a photograph of standard bullion coins after being treated by depletion gilding, according to some embodiments.

Figure 28 is a photograph of a rough-surface ring after being treated by depletion gilding, according to some embodiments.

Figure 29 is a photograph of a gold ring comprising cubic zirconia gemstone after being treated by depletion gilding, according to some embodiments.

Figure 30 is a photograph of a gold plate after being treated by depletion gilding, according to some embodiments.

Figures 31A-31B are photographs of a standard bullion coin before (Figure 31 A) and after (Figure 3 IB) being treated by the process described herein, according to some embodiments.

Figures 32A-32B are photographs of a gold leaf before (Figure 32A) and after (Figure 32B) being treated by the process described herein, according to some embodiments.

Figures 33A-33B are photographs of a gold ring before (Figure 33 A) and after (Figure 33B) being treated by the process described herein, according to some embodiments.

Figures 34A-34B are photographs of a gold necklace pendant before (Figure 34A) and after (Figure 34B) being treated by the process described herein, according to some embodiments.

Figures 35A-35F are photographs of three standard 9K-SCA5 gold alloys: an alloy gilded by the process described herein before (Figure 35 A) and after (Figure 35B) perspiration test; an alloy gilded by electroplating before (Figure 35C) and after (Figure 35D) perspiration test; and a fresh non-gilded alloy before (Figure 35E) and after (Figure 35F) perspiration test.

Figures 36A-36F are photographs of three standard 9K-OG130A gold alloys: an alloy gilded by the process described herein before (Figure 36A) and after (Figure 36B) perspiration test; an alloy gilded by electroplating before (Figure 36C) and after (Figure 36D) perspiration test; and a fresh non-gilded alloy before (Figure 36E) and after (Figure 36F) perspiration test.

Figures 37A-37F are photographs of three standard 9K-SCA5 gold alloys: an alloy gilded by the process described herein before (Figure 37A) and after (Figure 37B) corrosion test; an alloy gilded by electroplating before (Figure 37C) and after (Figure 37D) corrosion test; and a fresh non-gilded alloy before (Figure 37E) and after (Figure 37F) corrosion test.

Figures 38A-38F are photographs of three standard 9K-OG130A gold alloys: an alloy gilded by the process described herein before (Figure 38A) and after (Figure 38B) corrosion test; an alloy gilded by electroplating before (Figure 38C) and after (Figure 38D) corrosion test; and a fresh non-gilded alloy before (Figure 38E) and after (Figure 38F) corrosion test.

Figures 39A-39C are photographs of three standard 9K-SCA5 gold alloys: an alloy gilded by the process described herein (Figure 39A); an alloy gilded by electroplating (Figure 39B); and a fresh non-gilded alloy (Figure 39C); all after undergoing climate test.

Figures 40A-40C are photographs of three standard 9K-OG130A gold alloys: an alloy gilded by the process described herein (Figure 40A); an alloy gilded by electroplating (Figure 40B); and a fresh non-gilded alloy (Figure 40C); all after undergoing climate test.

DETAILED DESCRIPTION

In the following description, various aspects of the disclosure will be described. For the purpose of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the different aspects of the disclosure. However, it will also be apparent to one skilled in the art that the disclosure may be practiced without specific details being presented herein. Furthermore, well-known features may be omitted or simplified in order not to obscure the disclosure. In the figures, like reference numerals refer to like parts throughout.

Throughout the figures of the drawings, different superscripts for the same reference numerals are used to denote different embodiments of the same elements. Embodiments of the disclosed devices and systems may include any combination of different embodiments of the same elements. Specifically, any reference to an element without a superscript may refer to any alternative embodiment of the same element denoted with a superscript. Components having the same reference number followed by different lowercase letters may be collectively referred to by the reference number alone. If a particular set of components is being discussed, a reference number without a following lowercase letter may be used to refer to the corresponding component in the set being discussed.

The present invention provides devices and processes for depletion gilding of gold alloys, such as jewelry. The processes and devices are intended to increase the gold concentration on gold alloy surfaces and hereby make gold alloys visually appear enriched in gold. Specifically, the apparatus and processes of the invention are applied for the removal of metals other than gold from the surface of a gold alloy, thereby enriching the presence of gold in the surface, making the alloy look more gilded and shiny, while maintaining the integrity and rigidity of the entire alloy. The removal of the non-gold metals from the surface of the alloy is achieved by heating the alloy, then immersing it in a corrosive composition comprising components that are chemically reactive towards metals other than gold. The reaction occurs primarily at the surface of the alloy. According to the process disclosed herein, the corrosive composition is solid (particles), but at the point of contact with the alloy, the corrosive composition is fluid, which is afforded through utilization of a fluidized bed reactor in the course of the process. Generally, the alloy is exposed, under appropriate conditions, to a fluidized bed reactor comprising the corrosive composition in a fluidized form. It was surprisingly found that employing the aforementioned procedure, provides highly gilded products, even when the starting products are made of low karat gold alloys.

The term 'fluid' as used herein in the context of the corrosive composition refers to a composition whose particles behave as fluid.

The terms "fluidized bed" and "fluidized bed reactor" as used herein, are interchangeable, and refer to a reactor in which a gas flow passes through solid particles (such as a powder) and causes the solid particles, or at least parts thereof, to behave like a fluid and therefore suspend within a reaction zone (the reaction zone being, for example, a space confined within boundaries of the reactor). As a result, the suspended solid particles behave like a fluid, and are referred to as fluidized solid matter.

The term "alloy" as used herein refers to a homogeneous mixture of two or more metallic elements. The alloy materials resulting from the mixture are generally characterized in metallic properties, such as high electrical and thermal conductivity, high melting and boiling points and high density and ductility, among others. An alloy may be a solid single- phase solution of metal elements. In some cases, a combination of metals, compared to each metal alone, may reduce the overall cost of the resultant alloy while preserving important properties, such as appearance and mechanical properties. In other cases, the combination of metals imparts synergistic properties to the constituent metal elements such as corrosion resistance or mechanical strength. Examples of alloys are gold alloys, silver alloys, steel, solder, brass, pewter, bronze and amalgams.

The term "dealloying" as used herein refers to a corrosion process performed on alloys. In suitable conditions one or more of the components which form the alloys are preferentially leached from the alloy material. Generally, the less noble metal, i.e. the metal more susceptible toward a chemical reaction, is removed from the alloy by a redox mechanism thereby enriching the alloy, or at least the surface thereof, with the components that did not leach. Thus, a dealloying process may result with partial dealloying or complete dealloying. In some embodiments, dealloying refers to the dealloying of a certain section of a gold alloy, typically, a section at the surface of the gold alloy. Dealloying at the surface may be complete or partial.

The term "depletion gilding" as used herein typically refers to a method for producing a layer rich with gold on an object made of gold alloy by removing the other alloying metals (other than gold) from its surface. In some embodiments, depletion gilding process is applied on an object in order to increase the purity of gold that is already present on the object's surface. In this process, the other metals are fully or partially etched away from the surface of the gold alloy by the use of acids, often in combination with heat. The most common etchant is nitric acid, which is an acidic and oxidative solution, which the alloy may be immersed there within.

In some embodiments, there is provided a process for dealloying a gold alloy, the process comprising: heating a gold alloy, having an outer surface, to a first temperature of at least 150°C for a first time period; wherein the process further comprises immersing said gold alloy in a fluidized composition comprising at least one salt, thereby obtaining a dealloyed gold alloy having a dealloyed outer surface.

In some embodiments, the process is carried out using the dealloying apparatus disclosed herein.

In some embodiments, the process is carried out using dealloying apparatus 100. In some embodiments, the step of heating the gold alloy to the first temperature precedes the step of immersing the gold alloy in a fluidized composition.

In some embodiments, the step of heating the gold alloy to the first temperature occurs after the step of immersing the gold alloy in a fluidized composition.

It is to be understood that "gold alloy" refers to an alloy comprising gold metal. It is to be further understood that "gold metal" refers to pure Au element in its atomic, i.e. non-ionic state, which has a zero oxidation state.

Gold alloys are mainly used for constructing jewelry items, such as rings, necklaces, earring, watches, bracelets, charms, chains, etc. as well as commodity, i.e. bullion coins or bars. Because of the softness of pure gold (24k), it is usually alloyed with base metals for its uses, such as, for the preparation of jewelry, altering its hardness and ductility, melting point, color and other properties. Alloys with low karat rating contain higher percentages of base metals, such as copper, silver, nickel, rhodium, zinc, platinum and/or palladium in the alloy compared to alloys with higher karat rating, or compared to pure gold. Typically, jewelry is manufactured using 22k, 21k, 18k, 14k, 10k or 9k, which represent reasonable tradeoff between the preferable physical properties and low cost of the non-golden metals, and the glare of gold metal. The fineness of gold alloys is typically given in terms of Karat value (K), which is determined as 24 times the mass of pure gold in the alloy (M_g) divided by the total mass of the alloy (M_a), as follows:

M

K = 24—^

M_a

For example, an 18k gold ring consists of about 75% gold w/w and about 25% other metals. The identity and relative content of the other metals influence the appearance and physical properties of the gold ring, as explained hereinbelow.

In some embodiments, the gold alloy comprises 20% to 98% gold. In some embodiments, the gold alloy comprises 25% to 90% gold. In some embodiments, the gold alloy comprises 30% to 75% gold. In some embodiments, the gold alloy comprises 35% to 50% gold. In some embodiments, the gold alloy comprises not more than 50% gold. In some embodiments, the gold alloy comprises not more than 40% gold.

In some embodiments, the gold alloy is about 5 to about 23 karat gold. In some embodiments, the gold alloy is about 6 to about 18 karat gold. In some embodiments, the gold alloy is about 6 to about 14 karat gold. In some embodiments, the gold alloy is about 9 to about 14 karat gold. In some embodiments, the gold alloy is not more than about 14 karat gold. In some embodiments, the gold alloy is not more than about 10 karat gold. In some embodiments, the gold alloy is about 9 karat gold.

It is to be understood that 'about' refers to ±15% of a specified value, preferably ±15% of a specified value. For example, in ' about 6 to about 18 karat gold' it is meant from 5.1 karat to 20.7 karat gold, or from 21.25% pure gold metal w/w to 86.25% pure gold metal w/w with respect to the total weight of the alloy.

Without wishing to be bound with any theory or mechanism of action, it was found that the combination of a depletion gilding process, using appropriate salts, and fiuidization (e.g. using fluidized bed), which allows the salts to behave approximately as fluids, results in a highly bright and gilded outer surface of the resulting alloy. Surprisingly, this phenomenon was witnessed even when starting from low karat gold alloy, i.e. an alloy, which includes less than 40% gold metal. Even more surprising, incorporation of the fluidized bed process into depletion gilding for alloys having various karat values yielded the desired results.

In some embodiments, the gold alloy comprises at least one base metal. In some embodiments, the gold alloy comprises at least two base metals. In some embodiments, the gold alloy comprises one base metal. In some embodiments, the gold alloy comprises two base metals. In some embodiments, the gold alloy comprises one or two base metals.

The term "base metal", as used herein, refers to a metal, which is the more common and inexpensive of the metallic components of an alloy. Generally, common base metal include inexpensive metals, such as iron, nickel, lead, zinc and copper. When referring to gold alloys, even more expensive metals, such as, but not limited to, rhodium, platinum, silver and palladium may be used as base metals.

In some embodiments, the base metal(s) is selected from the group consisting of copper, zinc, platinum, silver, nickel, aluminum, iron, indium, cobalt, rhodium and palladium. Each option represents a separate embodiment. In some embodiments, the base metal(s) is selected from copper, zinc and silver. In some embodiments, the base metal is copper. In some embodiments, the base metal is silver. In some embodiments, the base metal is zinc. In some embodiments, the base metals are copper, zinc and silver.

The color of gold alloys is dependent upon their composition, i.e. in addition to the karat rate, it is dependent upon the identity and relative amount of the base metals in the alloy. The most common gold alloy composition for the manufacturing of jewelry includes white gold and yellow gold. Typically, yellow gold alloys are produced from a combination of gold and silver, zinc and copper as base metals, while white gold alloys are produced from a combination of gold and nickel, palladium, zinc, silver and copper as base metals. White gold alloys may also be produced from a combination of gold and palladium or platinum and/or silver as base metals.

The color of gold metal is shiny bright yellow. As the process disclosed herein removes base metals from the outer surfaces of gold alloys, the outer surfaces become enriched in gold content and may reflect the native color of pure gold. Alternatively, the process disclosed herein may enrich alloys, which have low content of gold (e.g. 9K gold alloys) to appear as gold alloys which have higher karat values (e.g. 18K). As a result, the process disclosed herein may be specifically useful for gilding yellow gold. In some embodiments, the gold alloy is a yellow gold alloy.

In some embodiments, the gold alloy comprises copper, silver, nickel, zinc, platinum rhodium and/or palladium. In some embodiments, the gold alloy comprises at least one of silver, zinc and copper. In some embodiments, the gold alloy comprises copper, silver and/or zinc. In some embodiments, the gold alloy comprises copper and silver. In some embodiments, the gold alloy consists of gold, copper and silver.

As the outer surface of non-gilded gold alloys contains gold and base metals, it is an object of the gilding process to selectively remove base metals, while maintaining the gold atoms intact in the outer surface of the alloy. The removal may be full or partial removal of the base metals based on the target product. One of the factors that enables a selective removal of base metals is the high resistivity of gold toward chemical reactions. Specifically Au(0) is highly resistant toward oxidation due to its relatively high reduction potential, which makes it the most noble of the noble metals. As a result, the less noble metals constructing the alloy may react with oxidizing compositions faster than gold, which allow their removal as oxidized ions. In order to achieve a selective dealloying reaction, which will oxidize and remove base metals and leave unreacted gold in the surface of the alloy, several factors were evaluated. Specifically, it was found that elevated temperatures, within the range of 200°C to 1,500°C and dealloying reaction times within the range of several seconds up to a few hours (e.g. 1 to 2 hours) tend to promote such a reaction.

In some embodiments, heating said gold alloy to the first temperature is conducted for a time period within the range of 1 second to 240 minutes. In some embodiments, heating said gold alloy to the first temperature is conducted for a time period within the range of 1 to 120 minutes. In some embodiments, heating said gold alloy to the first temperature is conducted for a time period within the range of 5 to 120 minutes. In some embodiments, heating said gold alloy to the first temperature is conducted for a time period within the range of 10 to 90 minutes.

In some embodiments, the first temperature is at least 200°C. In some embodiments, the first temperature is at least 250°C. In some embodiments, the first temperature is at least 300°C. In some embodiments, the first temperature is at least 350°C. In some embodiments, the first temperature is at least 400°C. In some embodiments, the first temperature is at least 450°C. In some embodiments, the first temperature is within the range of 300°C to 700°C. In some embodiments, the first temperature is within the range of 400°C to 600°C. In some embodiments, the first temperature is about 500°C.

In some embodiments, the step of heating the gold alloy to the first temperature precedes the step of immersing the gold alloy in a fluidized composition.

Generally, the step of heating the gold alloy may be performed prior to immersing the alloy in the fluidized solid composition. Stated otherwise, the heated alloy may contact the composition, when the composition is in a fluidized form. This order may be beneficial in some cases, as heating may promote the adhesion of the fluidized composition to the hot alloy. In some embodiments, the step of heating to the first temperature may be performed before, during and/or after immersing the alloy in the fluidized composition. In some embodiments, the step of heating is performed before, during and after immersing the alloy in the fluidized composition. In some embodiments, the step of heating is performed before and after immersing the alloy in the fluidized composition. In some embodiments, the step of heating is performed only before immersing the alloy in the fluidized composition. In some embodiments, the step of heating is performed only after immersing the alloy in the fluidized composition. It is also contemplated that the first heating process is maintained or commenced, during the immersion of the alloy in the fluidized composition. In some embodiments, two heating steps are performed, the first (first temperature, Tl) occurs prior to immersion in the fluidized composition, and the second (second temperature, T2) occurs after the alloy was immersed in the fluidized composition.

In some embodiments, the immersing is followed by heating to a second temperature T2 of at least 150°C, for a second time period.

In some embodiments, the heating to the second temperature T2 is conducted while the alloy is in contact with the composition.

In some embodiments, the heating to the second temperature T2 is conducted while the alloy is immersed within the composition.

In some embodiments, the second temperature T2 to which the gold alloy is heated is at least 200°C. In some embodiments, the second temperature T2 is at least 250°C. In some embodiments, the second temperature T2 is at least 300°C. In some embodiments, the second temperature T2 is at least 350°C. In some embodiments, the second temperature T2 is at least 400°C. In some embodiments, the second temperature T2 is at least 450°C. In some embodiments, the second temperature T2 is in the range of 300°C to 700°C. In some embodiments, the second temperature T2 is in the range of 400°C to 600°C. In some embodiments, the second temperature T2 is about 500°C.

In some embodiments, the second time period is in the range of seconds, for example, 1 sec to 60 seconds, or 5 to 120 seconds. In some embodiments, the second time period is in the range of 1 sec to 240 minutes. In some embodiments, the second time period is in the range of 1 to 240 minutes. In some embodiments, the second time period is in the range of 5 to 120 minutes. In some embodiments, the second time period is in the range of 10 to 90 minutes.

In cases that no heating is performed prior to immersion of the alloy in the fluidized composition, it may be advantageous to employ other means for increasing adhesion between the alloy and the composition, such as applying viscous liquids on the alloy surface prior to immersion in the fluidized composition. In some embodiments, the process further comprises a step of dipping the alloy in a concentrated aqueous solution containing water-soluble salts. It is to be understood that increasing a salt concentration in an aqueous solution results in increasing the viscosity of the solution, which results in its ability to serve as an adhesive. Thus, the alloy covered by a layer of a concentrated aqueous solution is adhesive towards the fluidized composition, such that upon immersing the gold alloy in a fluidized solid composition, the alloy-fluidized composition is ready for the heating and reaction.

In some embodiments, the process further comprises a step of dipping the alloy in a liquid prior to immersing said gold alloy in the fluidized solid composition comprising at least one salt. In some embodiments, the process further comprises a step of dipping the alloy in a liquid prior to immersing said gold alloy in the fluidized solid composition comprising at least one salt, wherein the process is devoid of heating the alloy prior to immersing the gold alloy in the fluidized solid composition. In some embodiments, dipping the alloy in the liquid is followed by to immersing the gold alloy in the fluidized solid composition without drying the alloy from the liquid. In some embodiments, dipping the alloy in the liquid is followed by immersing the gold alloy in the fluidized solid composition, which is followed by heating the alloy to the first temperature. In some embodiments, dipping the alloy in the liquid is followed by immersing the gold alloy in the fluidized solid composition, which occurs simultaneously with the heating of the alloy to the first temperature.

In some embodiments, the liquid is viscous. In some embodiments, the liquid comprises an aqueous solution. In some embodiments, the aqueous solution comprises at least one water soluble salt. In some embodiments, the aqueous solution is saturated with the at least one water soluble salt. In some embodiments, the aqueous solution is concentrated with the at least one water soluble salt. In some embodiments, the aqueous solution comprises the same salt as the at least one salt in the fluidized solid composition comprising. In some embodiments, the process further comprises a step of dipping the alloy in a saturated solution of water soluble salt(s) prior to immersing said gold alloy in the fluidized solid, wherein the process is devoid of heating the alloy prior to immersing the gold alloy in a fluidized solid composition.

The term "concentrated" as used herein with reference to aqueous solutions, refers to an aqueous solution, in which at least one salt is dissolved in a concentration of at least 0.5M, 1M, 1.5M, 2M, 2.5M, 3M, 3.5M, 4M, 4.5M, 5M, 7.5M or at least 10M.

Another advantage of the process disclosed herein is that it achieves parametric control over the hue of resulting alloy. As the process may be implemented using a machine, i.e. the device disclosed herein, it is possible to control parameters, such as the first temperature; the heating duration; the number of heating cycles, the duration of immersing the alloy in the fluidized composition, the second temperature, the duration of heating to the second temperature, etc. It was found that the resulting hue may be tailor-made, based on such parameters, which are provided as input to the device control by the operator through the user interface (UI). Moreover, different karat rate alloys may require different parameters, which are under the control of the user, when implementing the process using the device disclosed herein. In addition, a selective control over the resulting hue of the gold alloy may further be influenced by the identity and relative amount of each base metal in the starting alloy. Another added value of the process disclosed herein over the traditional electroplating techniques stems from the fact that it is suitable for soldered jewelry items. For example, many rings and watches are made by soldering gold alloys to silver, which results in a combination of gold and silver, attached to one another. Such jewelry items may need to be gilded at some point. However, electroplating techniques cannot achieve the goal of effectively gilding only the gold area/segments/parts and result in complete coverage, namely, covering both the silver and the gold areas on the surface of an alloy characterized by a pattern that includes graphics and/or texture made of silver. Similar restriction applies if the pattern is made of materials other than gold, such as, platinum, pearl and diamonds among others. In contrast, the process disclosed herein can selectively enrich the gold area(s) without affecting patterns made of other materials, for example, graphics of texture made of silver. Specifically, process parameters may be selected such that the effect on gold and silver is scarce, while the removal of base metals from the gold alloy is much more significant.

Further, in order to achieve a selective dealloying reaction as discussed above, appropriate etchant composition should be selected. As mentioned above the most common etchant in depletion gilding is nitric acid, as it is both acidic, oxidative and it is in the form of liquid into which gold alloys can be immersed. Gold alloys are homogenously dispersed in liquid solutions, which made nitric acid the etchant of choice for most early depletion gilding processes known in the art. However, nitric acid suffers from two main disadvantages. First, the dealloying reaction temperature has to be kept relatively low (below 150 °C) and cannot be modified and optimized, when using volatile aqueous solutions, as nitric acid. Second, nitric acid is highly acidic and has a very high oxidation potential, which prevents from introducing any modification to the reaction parameters. As a result, solid compositions are advantageous for gilding as they avoid problems of maximal temperature threshold, and can be modified using different etchants in the composition, such that optimal dealloying reaction parameters and conditions are attained.

Thus, in order to achieve a dealloying reaction, which is selective and optimal in terms of reaction parameters and conditions, an appropriate solid etchant composition should be selected. Since chemical salts are solids and may be chemically reactive, this family of compounds was selected as etchant. Appropriate salt(s) which may be included in the composition, include salts and salts mixtures that are thermally stable and are having high reactivity towards base metals, but not towards gold. Specifically, it was found that preferable salt mixtures include a combination of: (i) a mildly acidic salt having pKa around 8.5-10; and (ii) a salt having a relatively high oxidation potential, such as nitrate salts.

The term 'thermally stable' as used herein refers to compounds that are relatively stable under high temperatures, about 100°C or about 200°C, and do not decompose or otherwise disintegrate.

In some embodiments, the composition comprises a plurality of salts. In some embodiments, the composition comprises at least two salts. In some embodiments, the composition comprises two salts. In some embodiments, the fluidized composition comprises a plurality of salts. In some embodiments, the fluidized composition comprises two salts.

In some embodiments, the composition includes at least one inorganic salt. In some embodiments, the composition includes a plurality of inorganic salts. In some embodiments, the composition includes two inorganic salts. In some embodiments, the composition includes at least one organic salt. In some embodiments, the composition includes a plurality of organic salts. In some embodiments, the composition includes two organic salts. In some embodiments, the at least one organic salt comprises at least one carboxylic acid. In some embodiments, the at least one organic salt comprises oxalic acid. . In some embodiments, the at least one organic salt comprises at least one organophosphate functional group. In some embodiments, the fluidized composition comprises at least one salt having a pKa below 12. In some embodiments, the fluidized composition comprises at least one salt having a pKa below 11. In some embodiments, the fluidized composition comprises at least one salt having a pKa below 10.5. In some embodiments, the fluidized composition comprises at least one salt having a pKa below 10. In some embodiments, the fluidized composition comprises at least one salt having a pKa in the range of 4 to 12. In some embodiments, the fluidized composition comprises at least one salt having a pKa in the range of 6 to 11. In some embodiments, the fluidized composition comprises at least one salt having a pKa in the range of 8 to 10.5. In some embodiments, the fluidized composition comprises at least one salt having a pKa in the range of 8.5 to 10.

In some embodiments, the fluidized composition comprises at least one ammonium salt. In some embodiments, the fluidized composition comprises one ammonium salt. In some embodiments, the fluidized composition comprises at least salt having a protonated nitrogen atom.

The term "ammonium salt" as used herein refers to an ionic compound having a cation of the formula R 1 R2 R3 R4 N+ , where each one of R 1 , R2 , R3 and R 4 may separately be hydrogen or alkyl. Example of ammonium salt include, but are not limited to, NH₄CI, CH₃CO₂NH₄, (NH₄)₂C0₃, NtL_tBr, (C₄H₉)₃NH and (C₈Hi₇)Me₂NH. In some embodiments, the ammonium salt comprises a NtL_t ⁺ cation. In some embodiments, the ammonium salt is selected from the group consisting of NH₄CI, CH3CO₂NH₄, (NH^COs, NH₄HCO3, NtLtBr, NH₄I, NH₄NO3, NH4HSO4, (NH4)₂S0₄, Ce(NH4)₄(S0₄)4, (NH4)₂Ce(N0₃)6, (NH4)₂Cr0₄, (NH4)₂Cr₂0₇ and NH₄H₂P0₄. Each option represents a separate embodiment. In some embodiments, the ammonium salt is NH₄CI.

In some embodiments, the composition comprises at least one salt comprising an anion selected from chloride, nitrate and sulfate. In some embodiments, the composition comprises at least one salt comprising a nitrate anion. In some embodiments, the composition comprises at least one salt comprising a chloride anion. In some embodiments, the nitrate salt is selected from the group consisting of NH4NO3, KN0₃, NaN0₃, L1NO3, NH4NO3, NH4NO3, Pb(N0₃)₂, A1(N0₃), Mg(N0₃)₂, Ca(N0₃)₂, (NH4)₂Ce(N0₃)₆, Cr(N0₃)₃ and Zn(N0₃)₂. Each option represents a separate embodiment. In some embodiments, the nitrate salt is KNO₃.

In some embodiments, the composition comprises at least one salt selected from the group consisting of NH4CI, CH₃C0₂NH4, (NH4)₂C0₃, NH4HCO3, NtLtBr, NH4I, NH4NO3, NH4HSO4, (NH4)₂S0₄, Ce(NH4)₄(S0₄)4, (NH4)₂Ce(N0₃)6, (NH4)₂Cr0₄, (NH4)₂Cr₂0₇ and NH4H₂P0₄, KNO3, NaN0₃, L1NO3, NH4NO3, Pb(N0₃)₂, A1(N0₃), Mg(N0₃)₂, Ca(N0₃)₂, Cr(N0₃)3 and Ζη(Ν(¾)₂. Each option represents a separate embodiment. In some embodiments, the composition comprises at least two salts selected from the group consisting of NH₄CI, CH₃C0₂NH₄, (NH₄)₂C0₃, NH₄HCO3, NtLtBr, NH₄I, NH₄NO3, NH4HS0₄, (NH4)₂S0₄, Ce(NH4)₄(S0₄)₄, (NH4)₂Ce(N0₃)6, (NH4)₂Cr0₄, (NH4)₂Cr₂0₇ and NH4H₂P0₄, KNO3, NaN0₃, L1NO3, NH4NO3, Pb(N0₃)₂, A1(N0₃), Mg(N0₃)₂, Ca(N0₃)₂, Cr(N0₃)₃ and Zn(N(¾)₂. Each option represents a separate embodiment. In some embodiments, the composition comprises at least one salt selected from the group consisting of NH₄CI, CH₃C0₂NH₄, (NH₄)₂C0₃, NH₄HCO3, NtLtBr, NH₄NO3, NH₄HS0₄, (NH₄)₂S0₄, (NH4)₂Ce(N03)6, (NH4)₂Cr₂0₇, KNO3 and NaN0₃. In some embodiments, the composition comprises at least two salts selected from the group consisting of NH₄CI, CtbCChNtLt, (NH4)₂C0₃, NH4HCO3, NtLtBr, NH4NO3, NH4HS0₄, (NH4)₂S0₄, (NH4)₂Ce(N0₃)6, (NH₄)₂Cr₂0₇, KNO₃ and NaN(¾. In some embodiments, the composition comprises at least one nitrate salt and at least one ammonium salt. In some embodiments, the composition comprises KNO3 and NH4CI.

In some embodiments, the composition further comprises at least one compound selected from the group consisting of KA1(S0₄)₂, FeSC , NaN(¾, ZnS0₄, oxalic acid and NH₄NO₃. Each option represents a separate embodiment. As mentioned above, the employment of a solid etchant composition comprising chemically reactive salts is preferred for the process disclosed herein. Two obstacles, which are encountered when using solid salts, include (i) reactions between two reactant solids, such as metal alloys and salts, are ordinarily very sluggish, due to the separation of phases; and (ii) the dealloying reaction is non-homogeneous on the outer surface of the alloy, leaving the product gilded alloy with high surface variability, i.e. with areas, which were intensively reacted, on the side of poorly gilded area. The process disclosed herein manages to circumvent these obstacles through the employment of the fluidized bed technique, which is explained in detail herein, and is generally intended to fluidize solid compositions, such that they act as if they were fluid. It was also found that the fluidization process is improved when using salt in the form of powders.

The term "immersing" as used herein denotes contacting with, plunging into, or dipping into, fluid medium or a fluidized solid medium. The term is by no means limited to dipping of an object in a liquid, but it also encompasses immersing objects in a fluidized solid media, such as solid-gas dispersions. For example, "immersing" includes suspending or depositing an object in aerosols, including liquid aerosols and solid aerosols, such as smoke, cloud, air particulates, dust, fog and mist.

In some embodiments, the at least one salt is provided prior to said immersing in a solid form, and the process further comprises fluidizing said at least one salt, thereby obtaining a fluidized composition.

In some embodiments, fluidizing the at least one salt is conducted for a period of time within the range of a few seconds. In some embodiments, fluidizing the at least one salt is conducted for a period of time within the range of 1 second to 60 seconds. In some embodiments, fluidizing the at least one salt is conducted for a period of time within the range of 5 seconds to 120 seconds. In some embodiments, fluidizing the at least one salt is conducted for a period of time within the range of 1 second to 240 minutes. In some embodiments, fluidizing the at least one salt is conducted for a period of time in the range of 1 to 240 minutes, 5 to 120 minutes, or 10 to 90 minutes.

In some embodiments, fluidizing the at least one salt is conducted in a fluidized bed reactor. In some embodiments, the composition is in the form of a powder (particles). In some embodiments, the at least one salt is in the form of a powder. In some embodiments, the at least one salt has particles having MMAD of no more than 500 micrometer. In some embodiments, the salt(s) has particles having MMAD of no more than 400 micrometer. In some embodiments, the salt(s) has particles having MMAD of no more than 300 micrometer. In some embodiments, the salt(s) has particles having MMAD of no more than 200 micrometer. In some embodiments, the salt(s) has particles having MMAD of no more than 100 micrometer. In some embodiments, the salt(s) has particles having MMAD of no more than 50 micrometer. In some embodiments, the salt(s) has particles having MMAD of no more than 25 micrometer.

In some embodiments, the fluidized composition comprises particles having MMAD of no more than 500 micrometer. In some embodiments, the fluidized composition comprises particles having MMAD of no more than 400 micrometer. In some embodiments, the fluidized composition comprises particles having MMAD of no more than 300 micrometer. In some embodiments, the fluidized composition comprises particles having MMAD of no more than 200 micrometer. In some embodiments, the fluidized composition comprises particles having MMAD of no more than 100 micrometer. In some embodiments, the fluidized composition comprises particles having MMAD of no more than 50 micrometer. In some embodiments, the fluidized composition comprises particles having MMAD of no more than 25 micrometer.

In some embodiments, the fluidized composition comprises particles having MMAD of no more than 30 micrometer. In some embodiments, the fluidized composition comprises particles having MMAD of no more than 15 micrometer. In some embodiments, the fluidized composition consists essentially of particles having MMAD of no more than 30 micrometer. In some embodiments, the fluidized composition consists essentially of particles having MMAD of no more than 15 micrometer.

The term 'mass median aerodynamic diameter', also known as MMAD, as used herein is commonly considered as the median particle diameter by mass.

In some embodiments, the step of fluidizing the composition in the fluidized bed reactor is preformed simultaneously with the step of immersing the alloy with the fluidized composition. In some embodiments, the fluidized bed reactor produces a mist from the solid composition. In some embodiments, the fluidized composition in the form of a mist is drifted in the direction of the reactor's gas current, thereby contacting the gold alloy. In some embodiments, immersing the gold alloy in the composition is performed during fluidizing the composition. In some embodiments, the steps of fluidizing the composition and immersing the alloy in the fluidized composition are performed using a dealloying apparatus as disclosed herein.

In some embodiments, the immersing is followed by washing the dealloyed gold alloy.

It is to be understood that after the dealloying is complete, residues of the fluidized composition are left on the resultant gilded alloy. For removing the residues, a subsequent step of further washing the alloy may be required.

The term "washing" as used herein is interchangeable with the term "rinsing" and refers to the step of removing compositions and products that remain on the surface of the gold alloy after the immersing step or the second heating step. Washing is typically performed with aqueous solutions, such as, de-ionized water or tap water. Other methods or materials for removing residuals from surface can be applied. Alternatively, or in addition, Brush-like tools can be used to wash the surface.

In some embodiments, the washing occurs after the immersing of the gold alloy in a fluidized solid composition. In some embodiments, the washing occurs after the heating of the alloy to the first temperature. In some embodiments, the washing occurs after the heating to the second temperature T2. In some embodiments, the washing occurs after the alloy underwent (natural or induced) cooling from T2 to 50°C, 40°C, 30°C or room temperature. In some embodiments, the washing occurs no more than 5, 3 or 1 minutes after the heating to the second temperature T2. In some embodiments, the washing occurs immediately after the heating to the second temperature T2.

In some embodiments, the washing is performed in a temperature in the range of 0 - 400°C. In some embodiments, the washing is performed in a temperature in the range of 0 - 50°C. In some embodiments, the washing is performed in a temperature in the range of 25 - 100°C. In some embodiments, the washing is performed in a temperature in the range of 50 - 150°C. In some embodiments, the washing is performed in a temperature in the range of 100 - 200°C. In some embodiments, the washing is performed in a temperature in the range of 150 - 300°C. In some embodiments, the washing is performed in a temperature in the range of 200 - 400°C. In some embodiments, the washing is performed in a temperature in the range of 250 - 350°C. In some embodiments, the washing is performed in room temperature. In some embodiments, the washing is performed at a temperature less than 100°C.

Performing the process disclosed herein on gold alloys can result in removal of base metals from a relatively thin layer at the surface of the alloy, also termed herein, the outer surface of the alloy. As a result, the color of the alloy seems bright golden. For most gold alloys it is required to obtain no more than a thin dealloyed layer, since high concentrations of hard base metals within the alloy are required for maintaining rigidity among other physical properties. Thus, the dealloying apparatus and processes disclosed herein are advantageous as they generate a sufficiently thin gold layer at the surface of the alloy, while maintaining the remaining structure of the alloy.

In some embodiments, the dealloyed outer surface has a thickness in the range of 1 to 5 nanometers. In some embodiments, the dealloyed outer surface has a thickness in the range of 1 to 10 nanometers. In some embodiments, the dealloyed outer surface has a thickness in the range of 1 to 100 nanometers. In some embodiments, the dealloyed outer surface has a thickness in the range of 10 to 100 nanometers. In some embodiments, the dealloyed outer surface has a thickness in the range of 20 to 100 nanometers. In some embodiments, the dealloyed outer surface has a thickness in the range of 1 to 75 nanometers. In some embodiments, the dealloyed outer surface has a thickness in the range of 1 to 50 nanometers. In some embodiments, the dealloyed outer surface has a thickness in the range of 10 to 50 nanometers. In some embodiments, the dealloyed outer surface has a thickness in the range of 15 to 40 nanometers. In some embodiments, the dealloyed outer surface has a thickness in the range of 0.01 to 1 micron. In some embodiments, the dealloyed outer surface has a thickness in the range of 0.05 to 5 micron. In some embodiments, the dealloyed outer surface has a thickness in the range of 0.1 to 3 micron. In some embodiments, the dealloyed outer surface has a thickness in the range of 0.1 to 2 micron. In some embodiments, the dealloyed outer surface has a thickness in the range of 0.2 to 1.7 micron. In some embodiments, the dealloyed outer surface has a thickness in the range of 0.2 to 1.5 micron. In some embodiments, the dealloyed outer surface has a thickness in the range of 0.25 to 1.25 micron. In some embodiments, the dealloyed outer surface has a thickness in the range of 0.5 to 1 micron.

In some embodiments, the outer surface is covering an inner core of the gold alloy. In some embodiments, dealloying the outer surface is substantially devoid of reacting the composition with the inner core. In some embodiments, the process is substantially devoid from dealloying the inner core. It is to be understood that process disclosed herein results in dealloying of the surface of a gold alloy, such that the outer surface of the dealloyed product has a metal concentration profile, rather than a constant concentration for each metal (See, for example Figure 24A, in which the concentration profile of gold is such that the concentration of gold is 96% in the outermost layer and gradually decreases until stabilizing at 88% gold, when exiting the surface into the core). Thus, upon penetrating deeper into the outer surface, the base metal concentration is increased and the concentration of gold is decreased. This trend is expected to continue until reaching the inner core, which is remained substantially unreacted, and thus is having the metal profile of the original alloy, prior to the dealloying.

The term "substantially devoid" when referring to chemical reaction is intended to mean to not more than 20%, preferably not more than 10%, and more preferably not more than 5%, 1 % or 0.1%. For example, the expression "substantially devoid from dealloying the inner core" means that after the process at least 80% of the base metal atoms in the inner core still remain in the inner core, rather than being consumed.

It is to be understood that although gold alloys typically have a homogeneous continuous phase, an outer surface and an inner core may be defined, where any part of the inner core is not included in the surface, and vice versa. It is further to be understood that although the term 'surface' is frequently defined as two dimensional, the surface of the gold alloy, as referred herein is three dimensional, having a relatively very low thickness, and thus it is approximately two dimensional.

The term " dealloying" when referring to chemical reaction of the surface of a gold alloy means that a part of the base metals included in the surface are oxidized and removed from the surface, which some are maintained in the surface. This term is not limited to low values and also includes high values, such as over 99%, which means that reacting and removing over 99%, but less than 100% of the base metals from the surface of the alloy is under the definition of "dealloying", when referring to the outer surface of the alloy.

In some embodiments, the outer surface comprises a first amount of base metals, and the dealloyed outer surface comprises less than 15% of the first amount of base metals. In some embodiments, the outer surface comprises a first amount of base metals, and the dealloyed outer surface comprises less than 30% of the first amount of base metals. In some embodiments, the outer surface comprises a first amount of base metals, and the dealloyed outer surface comprises less than 40% of the first amount of base metals. In some embodiments, the outer surface comprises a first amount of base metals, and the dealloyed outer surface comprises less than 50% of the first amount of base metals. In some embodiments, the outer surface comprises a first amount of base metals, and the dealloyed outer surface comprises less than 75% of the first amount of base metals. In some embodiments, the outer surface comprises a first amount of base metals, and the dealloyed outer surface comprises less than 90% of the first amount of base metals. In some embodiments, the outer surface comprises a first amount of base metals, and the dealloyed outer surface comprises less than 95% of the first amount of base metals. In some embodiments, the outer surface comprises a first amount of base metals, and the dealloyed outer surface comprises less than 99.9% of the first amount of base metals.

In some embodiments, dealloying the outer surface comprises removing at least 10% of the base metals from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 25% of the base metals from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 40% of the base metals from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 50% of the base metals from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 75% of the base metals from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 90% of the base metals from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 95% of the base metals from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 99.9% of the base metals from the outer surface.

In some embodiments, the outer surface comprises a first proportion of base metals, and the dealloyed outer surface comprises less than 75% of the first proportion of base metals. In some embodiments, the outer surface comprises a first proportion of base metals, and the dealloyed outer surface comprises less than 50% of the first proportion of base metals. In some embodiments, the outer surface comprises a first proportion of base metals, and the dealloyed outer surface comprises less than 25% of the first proportion of base metals.

It is to be understood that the phrase "proportion of base metals" refers to the relative amount of base metals in a defined object or substance. For example, if an outer surface of a gold alloy consists of 80% gold, 10% silver, 7% copper and 3% zinc, the proportion of gold in the outer surface is 0.80, the proportion of silver is 0.10, the proportion of copper is 0.07 and the proportion of zinc in this surface is 0.03. It is further to be understood that percentages of proportions refer to relative percentages, rather than to percentage points. For example, in case that the outer surface of the alloy described in this paragraph is gilded to form a gilded surface consisting of 95% gold, 4% silver, 1 % copper and no detectable zinc; the dealloyed outer surface in considered to comprise 119% of the first proportion of gold. It is also considered to comprise 40% of the first proportion of silver, 14% of the first proportion of copper, 0% of the first proportion of zinc and 25% of the first proportion of base metals ((0.04+0.01)/(0.10+0.07+0.03)=25%).

In some embodiments, the outer surface comprises a first amount of copper, and the dealloyed outer surface comprises less than 15% of the first amount of copper. In some embodiments, the outer surface comprises a first amount of copper, and the dealloyed outer surface comprises less than 30% of the first amount of copper. In some embodiments, the outer surface comprises a first amount of copper, and the dealloyed outer surface comprises less than 40% of the first amount of copper. In some embodiments, the outer surface comprises a first amount of copper, and the dealloyed outer surface comprises less than 50% of the first amount of copper. In some embodiments, the outer surface comprises a first amount of copper, and the dealloyed outer surface comprises less than 75% of the first amount of copper. In some embodiments, the outer surface comprises a first amount of copper, and the dealloyed outer surface comprises less than 90% of the first amount of copper. In some embodiments, the outer surface comprises a first amount of copper, and the dealloyed outer surface comprises less than 95% of the first amount of copper.

In some embodiments, dealloying the outer surface comprises removing at least 15% of the copper from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 30% of the copper from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 40% of the copper from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 50% of the copper from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 75% of the copper from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 90% of the copper from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 95% of the copper from the outer surface.

In some embodiments, the outer surface comprises a first proportion of copper, and the dealloyed outer surface comprises less than 75% of the first proportion of copper. In some embodiments, the outer surface comprises a first proportion of copper, and the dealloyed outer surface comprises less than 50% of the first proportion of copper. In some embodiments, the outer surface comprises a first proportion of copper, and the dealloyed outer surface comprises less than 25% of the first proportion of copper.

In some embodiments, the outer surface comprises a first amount of silver, and the dealloyed outer surface comprises less than 15% of the first amount of silver. In some embodiments, the outer surface comprises a first amount of silver, and the dealloyed outer surface comprises less than 30% of the first amount of silver. In some embodiments, the outer surface comprises a first amount of silver, and the dealloyed outer surface comprises less than 40% of the first amount of silver. In some embodiments, the outer surface comprises a first amount of silver, and the dealloyed outer surface comprises less than 50% of the first amount of silver. In some embodiments, the outer surface comprises a first amount of silver, and the dealloyed outer surface comprises less than 75% of the first amount of silver. In some embodiments, the outer surface comprises a first amount of silver, and the dealloyed outer surface comprises less than 90% of the first amount of silver. In some embodiments, the outer surface comprises a first amount of silver, and the dealloyed outer surface comprises less than 95% of the first amount of silver.

In some embodiments, dealloying the outer surface comprises removing at least 15% of the silver from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 30% of the silver from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 40% of the silver from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 50% of the silver from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 75% of the silver from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 90% of the silver from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 95% of the silver from the outer surface.

In some embodiments, the outer surface comprises a first proportion of silver, and the dealloyed outer surface comprises less than 75% of the first proportion of silver. In some embodiments, the outer surface comprises a first proportion of silver, and the dealloyed outer surface comprises less than 50% of the first proportion of silver. In some embodiments, the outer surface comprises a first proportion of silver, and the dealloyed outer surface comprises more than 100% of the first proportion of silver. In some cases, it may be desirable to enrich the outer surface with silver, which is also a rather expensive metal. It is described herein that based on the alloy composition and predetermined process factors (e.g. dealloying times and temperatures) the product alloy may be enriched in both silver and gold. Without wishing to be bound by any theory or mechanism, the silver enrichment may be the result of the relative inertness of silver towards the salt composition. In these cases, other base metals (e.g. zinc and copper) are rapidly removed from the surface leaving the outer surface enriched in higher concentrations of gold and silver.

In some embodiments, the outer surface comprises a first proportion of silver, and the dealloyed outer surface comprises more than 150% of the first proportion of silver. In some embodiments, the outer surface comprises a first proportion of silver, and the dealloyed outer surface comprises more than 200% of the first proportion of silver. In some embodiments, the outer surface comprises a first proportion of silver, and the dealloyed outer surface comprises more than 300% of the first proportion of silver.

In some embodiments, the outer surface comprises a first amount of silver, and the dealloyed outer surface comprises at least 70% of the first amount of silver. In some embodiments, the outer surface comprises a first amount of silver, and the dealloyed outer surface comprises at least 75% of the first amount of silver. In some embodiments, the outer surface comprises a first amount of silver, and the dealloyed outer surface comprises at least 80% of the first amount of silver. In some embodiments, the outer surface comprises a first amount of silver, and the dealloyed outer surface comprises at least 85% of the first amount of silver. In some embodiments, the outer surface comprises a first amount of silver, and the dealloyed outer surface comprises at least 90% of the first amount of silver. In some embodiments, the outer surface comprises a first amount of silver, and the dealloyed outer surface comprises at least 95% of the first amount of silver. In some embodiments, the outer surface comprises a first amount of silver, and the dealloyed outer surface comprises at least 99% of the first amount of silver.

In some embodiments, dealloying the outer surface comprises removing not more than 30% of the silver from the outer surface. In some embodiments, dealloying the outer surface comprises removing not more than 25% of the silver from the outer surface. In some embodiments, dealloying the outer surface comprises removing not more than 20% of the silver from the outer surface. In some embodiments, dealloying the outer surface comprises removing not more than 15% of the silver from the outer surface. In some embodiments, dealloying the outer surface comprises removing not more than 10% of the silver from the outer surface. In some embodiments, dealloying the outer surface comprises removing not more than 5% of the silver from the outer surface. In some embodiments, dealloying the outer surface comprises removing not more than 1 % of the silver from the outer surface.

In some embodiments, the outer surface comprises a first amount of zinc, and the dealloyed outer surface comprises less than 15% of the first amount of zinc. In some embodiments, the outer surface comprises a first amount of zinc, and the dealloyed outer surface comprises less than 30% of the first amount of zinc. In some embodiments, the outer surface comprises a first amount of zinc, and the dealloyed outer surface comprises less than 40% of the first amount of zinc. In some embodiments, the outer surface comprises a first amount of zinc, and the dealloyed outer surface comprises less than 50% of the first amount of zinc. In some embodiments, the outer surface comprises a first amount of zinc, and the dealloyed outer surface comprises less than 75% of the first amount of zinc. In some embodiments, the outer surface comprises a first amount of zinc, and the dealloyed outer surface comprises less than 90% of the first amount of zinc. In some embodiments, the outer surface comprises a first amount of zinc, and the dealloyed outer surface comprises less than 95% of the first amount of zinc. In some embodiments, the outer surface comprises a first amount of zinc, and the dealloyed outer surface comprises less than 99% of the first amount of zinc.

In some embodiments, dealloying the outer surface comprises removing at least 15% of the zinc from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 30% of the zinc from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 40% of the zinc from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 50% of the zinc from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 75% of the zinc from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 90% of the zinc from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 95% of the zinc from the outer surface. In some embodiments, dealloying the outer surface comprises removing at least 99% of the zinc from the outer surface.

In some embodiments, the outer surface comprises a first proportion of zinc, and the dealloyed outer surface comprises less than 25% of the first proportion of zinc. In some embodiments, the outer surface comprises a first proportion of zinc, and the dealloyed outer surface comprises less than 10% of the first proportion of zinc. In some embodiments, the outer surface comprises a first proportion of zinc, and the dealloyed outer surface comprises less than 5% of the first proportion of zinc. In some embodiments, the outer surface comprises a first proportion of zinc, and the dealloyed outer surface comprises less than 2% of the first proportion of zinc.

In some embodiments, the outer surface comprises a first amount of gold, and the dealloyed outer surface comprises at least 70% of the first amount of gold. In some embodiments, the outer surface comprises a first amount of gold, and the dealloyed outer surface comprises at least 75% of the first amount of gold. In some embodiments, the outer surface comprises a first amount of gold, and the dealloyed outer surface comprises at least 80% of the first amount of gold. In some embodiments, the outer surface comprises a first amount of gold, and the dealloyed outer surface comprises at least 85% of the first amount of gold. In some embodiments, the outer surface comprises a first amount of gold, and the dealloyed outer surface comprises at least 90% of the first amount of gold. In some embodiments, the outer surface comprises a first amount of gold, and the dealloyed outer surface comprises at least 95% of the first amount of gold. In some embodiments, the outer surface comprises a first amount of gold, and the dealloyed outer surface comprises at least 99% of the first amount of gold.

In some embodiments, dealloying the outer surface comprises removing not more than 30% of the gold from the outer surface. In some embodiments, dealloying the outer surface comprises removing not more than 25% of the gold from the outer surface. In some embodiments, dealloying the outer surface comprises removing not more than 20% of the gold from the outer surface. In some embodiments, dealloying the outer surface comprises removing not more than 15% of the gold from the outer surface. In some embodiments, dealloying the outer surface comprises removing not more than 10% of the gold from the outer surface. In some embodiments, dealloying the outer surface comprises removing not more than 5% of the gold from the outer surface. In some embodiments, dealloying the outer surface comprises removing not more than 1 % of the gold from the outer surface.

In some embodiments, the outer surface comprises a first proportion of gold, and the dealloyed outer surface comprises more than 100% of the first proportion of gold. In some embodiments, the outer surface comprises a first proportion of gold, and the dealloyed outer surface comprises more than 115% of the first proportion of gold. In some embodiments, the outer surface comprises a first proportion of gold, and the dealloyed outer surface comprises more than 150% of the first proportion of gold. In some embodiments, the outer surface comprises a first proportion of gold, and the dealloyed outer surface comprises more than 200% of the first proportion of gold.

In some embodiments, the process results in that the dealloyed outer surface contains at least 20% gold based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains at least 30% gold based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains at least 40% gold based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains at least 50% gold based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains at least 60% gold based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains at least 70% gold based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains at least 80% gold based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains at least 90% gold based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains at least 95% gold based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains at least 98% gold based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains at least 99.9% gold based on the total weight of the outer surface.

In some embodiments, the process results in that the dealloyed outer surface contains l%-75% silver based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains l%-50% silver based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains l %-30% silver based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains l %-25% silver based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains l%-20% silver based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains 1%-15% silver based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains 1%-12% silver based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains 1.5%-12% silver based on the total weight of the outer surface.

In some embodiments, the process results in that the dealloyed outer surface contains not more than 70% copper based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains not more than 60% copper based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains not more than 50% copper based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains not more than 40% copper based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains not more than 30% copper based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains not more than 25% copper based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains not more than 20% copper based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains not more than 15% copper based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains not more than 10% copper based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains not more than 5% copper based on the total weight of the outer surface.

In some embodiments, the process results in that the dealloyed outer surface contains not more than 50% zinc based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains not more than 40% zinc based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains not more than 25% zinc based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains not more than 15% zinc based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains not more than 10% zinc based on the total weight of the outer surface. In some embodiments, the process results in that the dealloyed outer surface contains not more than 5% zinc based on the total weight of the outer surface. Some embodiments, the process results in that the dealloyed outer surface contains not more than 2% zinc based on the total weight of the outer surface. Some embodiments, the process results in that the dealloyed outer surface contains not more than 1 % zinc based on the total weight of the outer surface.

In some embodiments, the outer surface has a first fineness, and the dealloyed outer surface has a second fineness, wherein the second fineness is higher than the first fineness by at least 0.1 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 0.2 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 0.3 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 0.4 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 0.5 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 0.6 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 0.7 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 0.8 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 0.9 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 1 Karat. In some embodiments, the second fineness is higher than the first fineness by at least 1.5 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 2 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 3 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 4 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 5 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 6 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 7 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 8 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 9 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 10 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 11 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 12 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 13 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 14Karats. In some embodiments, the second fineness is higher than the first fineness by at least 15 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 16 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 17 Karats. In some embodiments, the second fineness is higher than the first fineness by at least 18 Karats.

In some embodiments, the process parameters are predetermined to achieve the target appearance. For example, when starting with a 9K alloy and the target appearance is that of 14K gold, the temperatures and exposure times may be different than cases when the target appearance is that of 18K gold.

In some embodiments, the process results in that the dealloyed outer surface is having a color according to the L*a*b* system of: L* in the range of 50 to 99, a* in the range of 1-10 and b* in the range of 15-45. In some embodiments, the process results in that the dealloyed outer surface is having a color according to the L*a*b* system of: L* in the range of 50 to 99, a* in the range of 5-10 and b* in the range of 15-45. In some embodiments, the process results in that the dealloyed outer surface is having a color according to the L*a*b* system of: L* in the range of 50 to 99, a* in the range of 1 -5 and b* in the range of 15-45. In some embodiments, the process results in that the dealloyed outer surface is having a color according to the L*a*b* system of: L* in the range of 85 to 90, a* in the range of 1-5 and b* in the range of 25-42.

In some embodiments, the gold alloy is selected from the group consisting of jewelry, coins and decorations. In some embodiments, the gold alloy is an item of jewelry. In some embodiments, the item of jewelry is selected from the group consisting of rings, necklaces, watches, earrings, nose rings, body piercing rings, collars, chains, charms and bracelets.

As shown in Examples 1-4, the process disclosed herein is suitable for gilding a wide range of gold items. For example, Figure 27 presents the gilding of a standard bullion coin, which has stamping of letters and figures. The stamping was maintained through the process. In some embodiments, the gold alloy comprises a stamping.

The term "stamping" as used herein includes, but is not limited to letters, notes, signs, marks, characters, labels, imprints, figures and decorations, which are customary to coins, bars and/or jewelry items.

Another example is presented in Figure 28, where a rough-surface ring comprising grooves of about 0.5 mm is successfully gilded throughout the visible area (surface).

In some embodiments, the gold alloy comprises at least one groove on the outer surface. In some embodiments, the groove(s) have depth(s) of at least 50 micrometer, 100 micrometer, 250 micrometer or 500 micrometer.

Yet another example is presented in Figure 29, where a gold ring comprising cubic zirconia gemstone is successfully gilded without damaging the gemstones. In some embodiments, the item of jewelry comprises at least one gemstone. The term "gemstone" as used herein includes, but is not limited to, diamonds, zirconia, amber, ruby, sapphire, emerald, pearls and opal.

Reference is now made to Figures 1A-1D. Figures 1A and IB constitute views in perspective of a dealloying apparatus 100, with a fluidized bed reactor 300 located distally to a heating unit 200 and offset from heating unit 200, respectively, in some embodiments. Figures lc and Id constitute a side view and a front view, respectively, of dealloying apparatus 100, in some embodiments. Dealloying apparatus 100 comprises leverage unit 102, elongated transport member 110, heating unit 200 and fluidized bed reactor 300.

Elongated transport member 110 is attached to leverage unit 102 at transport member proximal end 114 and comprises a placement section 140 adjacent to transport member distal end 142 (hidden from view in Figures 1A-1D, visible for example in Figures 13A-13B) at the opposite end. Leverage unit 102 is configured to displace transport member distal end 142 in the proximal and distal directions.

In some embodiments, elongated transport member 110 is rigid. According to some embodiments, elongated transport member 110 is formed as a rod, movable in the proximal and distal directions by leverage unit 102.

In some embodiments, as depicted in Figures 1A-1D, leverage unit 102 comprises motion unit 116, distal rod connector 112, proximal rod connector 104, first motion rod 106 and second motion rod 108. In some embodiments, motion unit 116 comprises an electric or electromagnetic motor (e.g. servomotors, stepper motors). In some embodiments, motion unit 116 comprises a pneumatic or hydraulic motor. In some embodiments, motion unit 116 comprises a pneumatic or hydraulic piston. Motion unit 116 is functionally associated with distal rod connector 112. First motion rod 106 and second motion rod 108 are rigidly connected to distal rod connector 112 on their distal end, and to proximal rod connector 104 on their proximal end. First motion rod 106 and second motion rod 108 pass through first plate opening 122 and second plate opening 124 located in proximal plate 120. Elongated transport member 110 is rigidly connected to upper rod connector 104 at transport member proximal end 114. Elongated transport member 110 passes through main plate opening 126 located in proximal plate 120.

Motion unit 116 is configured to drive distal rod connector 112 in the proximal and distal directions. According to some embodiments, as depicted in Figures 1A-1D, motion unit 116 is configured to vertically drive distal rod connector 112 proximally and distally along the z-direction. The vertical movement of distal rod connector 112 results in vertical movement in the same direction of both first 106 and second 108 motion rods, due to their rigid connection to proximal rod connector 112, as well as a similar vertical motion of proximal rod connector 104 and elongated transport member 110.

In some embodiments, the length of first 106 and second 108 motion rods is identical.

In some embodiments, only one motion rod is rigidly connected between distal 112 and proximal 104 rod connector.

In some embodiments, more than two motion rods are rigidly connected between distal 112 and proximal 104 rod connector.

In some embodiments, at least one element with other geometrical features than a rod, such as a plate, connects between distal 112 and proximal 104 rod connector.

In some embodiments, the length of elongated transport member 110 is higher than the length of either one of rod connectors 104 or 106.

It is to be understood by a person skilled in the art that other means of driving elongated transport member 110 vertically in the z-direction can be applicable, for example, a motion unit directly or indirectly connected to transport member proximal end 114, lateral side of elongated transport member 110, or any other section of elongated transport member 110.

While elongated transport member 110 is depicted as a rigid rod, rigidly attached to leverage unit 102 configured to drive elongated transport member 110 in the distal and proximal direction, it will be understood by a person skilled in the art that other elongated transport member 110 and leverage unit 102 configurations are applicable, as long as elongated transport member 110 is attached to leverage unit 102 at transport member proximal end 114 and as long as transport member distal end 142 is movable in the proximal and distal directions by leverage unit 102.

In some embodiments, elongated transport member 110 is formed as a telescopic member, such that transport member distal end 142 is configured to move telescopically in the proximal and distal directions by leverage unit 102 (embodiment not shown).

In some embodiments, elongated transport member 110 is formed as a flexible member, such as, but not limited to, a cable, a wire, a string and the like. According to some embodiments, leverage unit 102 comprises a pulley or a real, such that a flexible elongated transport member 110 is reliable there around (embodiment not shown).

Within the context of this application, the term "proximal" generally refers to the side or end of any device or a component of a device, which is closer to transport member proximal end 114 when connected to leverage unit 102.

Within the context of this application, the term "distal" generally refers to the side or end of any device or a component of a device, which is opposite the "proximal end", and is farther from transport member proximal end 114 when connected to leverage unit 102.

In some embodiments, the proximal and distal directions are not aligned vertically along the z axis, but rather along a different axis, such as the x axis, the y axis, or any other straight axis (embodiment not shown).

The term "z direction", as used herein, refers to a direction along the z-axis, as depicted in Figure 1A.

The term "elongated", as used herein, refers to having a length at least one order larger than the width of the same member, when spread along a straight line.

In some embodiments, motion unit 116 is devoid of any type of motor, such that leverage unit 102 is configured to operate manually by an operator (embodiment not shown).

Reference is now made to Figures 2A-2C. Figures 2A and 2B constitute views in perspective of heating unit 200, from a top-side angle and from a bottom-side angle, respectively, in some embodiments. Figure 2C constitutes a bottom view of heating unit 200 in some embodiments. Heating unit 200 comprises heating unit first surface 210, heating unit second surface 220, heating unit outer surface 202, and at least one heating element (not shown) configured to generate heat within at least a portion of the heating unit internal shaft (not numbered) confined by heating unit first 210, second 220 and outer 202 surfaces. In some embodiments, heating unit 200 further comprises heating unit attachment members 204a, 204b, 204c and 204d, configured to connect to proximal plate 120 (see Figures 1A- ID).

The heating unit internal shaft of heating unit 200 comprises at least one heating unit opening, configured to allow passage of elongated transport member 110 there through. In some embodiments, the at least one heating unit opening comprises two openings, such as heating unit proximal opening 212 and heating unit distal opening 222. In some embodiments, as depicted in Figures 2A-2C, heating unit first surface 210 comprises heating unit proximal opening 212. In some embodiments, outer surface 202 comprises heating unit proximal opening 212 (embodiment not shown).

In some embodiments, attachment of heating unit attachment members 204A, 204B, 204C and 204D to proximal plate 120 is executed in a manner that aligns the center of heating unit proximal opening 212 with the center of main plate opening 126, so as to allow elongated transport member 110 to pass through both main plate opening 126 and heating unit proximal opening 212.

In some embodiments, the diameters of main plate opening 126 and heating unit proximal opening 212 are identical, configured to allow passage of elongated transport member 110 there through.

In some embodiments, the diameters of main plate opening 126 and heating unit proximal opening 212 are different, yet each is configured to allow passage of elongated transport member 110 there through.

In some embodiments, heating unit second surface 220 comprises heating unit distal opening 222. In some embodiments, outer surface 202 comprises heating unit distal opening 222, opposite to heating unit proximal opening 212 (embodiment not shown).

In some embodiments, the diameter of heating unit distal opening 222 is higher than the diameter of heating unit upper opening 212.

While heating unit 200 is depicted in Figures 2A-2C as a cylindrical heating unit, it is to be understood that the cross-sectional geometry of heating unit 200 is optionally different, such as a rectangular, elliptical, triangular or any other curvilinear or rectilinear cross- section.

In some embodiments, heating unit distal opening 222 is aligned with heating unit proximal opening 212, configured to allow the passage of at least elongated transport member 110 there through.

In some embodiments, heating unit 200 can comprise any number of heating unit attachment members, for example, at least one heating unit attachment member.

In some embodiments, heating unit 200 does not comprise any attachment members, instead being configured to attach heating unit first surface 210 directly to proximal plate 120. In some embodiments, apparatus 100 does not include a proximal plate 120, configured to embed any other means known in the art to locate heating unit 200 in a position configured to allow elongated transport member 110 pass through heating unit proximal opening 212.

In some embodiments, heating unit 200 further comprises at least one ventilation unit

(not shown), configured to provide uniform temperature distribution within the internal space of heating unit 200.

In some embodiments, heating unit 200 further comprises at least one heating unit heat sensor (not shown). In some embodiments, the at least one heating unit heat sensor can be a thermocouple, thermometer, an IR sensor, or a thermistor.

Reference is now made to Figures 3A-3B. In some embodiments, heating unit 200 further comprises first 152a and second 152b plate closures. Figures 3A and 3B constitute views in perspective of heating unit 200 with first 152a and second 152b plate closures in a close and an open state, respectively, in some embodiments. In some embodiments, first plate closure 152a and second plate closure 152b are located adjacent to the at least one heating unit opening. In some embodiments, first plate closure 152a and second plate closure 152b are located distal to heating unit distal surface 220, rigidly connected to first closure rod 156a and second closure rod 156b, respectively.

First 156a and second 156b closure rods are configured to slide either towards each other or away from one another, along an axis perpendicular to the direction of movement of elongated transport member 110. In some embodiments, as depicted in Figs 3A-3B, first 156a and second 156b closure rods are configured to slide horizontally along the x-direction either towards each other or away from one another. In the close state (see Figure 3A), first plate closure 152a and second plate closure 152b are in close proximity to each other, wherein said close proximity is in a range configured to minimize heat loss from the internal space of heating unit 200.

In some embodiments, said close proximity is configured to allow first plate closure 152a and second plate closure 152b to be in contact.

First plate closure 152a and second plate closure 152b comprise first plate recess 154a and second plate recess 154b, respectively. First plate recess 154a and second plate recess 154b are configured to form an opening, referred to as plate opening 154, when in the close state (see Figure 3A). In some embodiments, plate opening 154 is aligned with at least one of heating unit proximal opening 212 and heating unit distal opening 222, configured to allow passage of elongated transport member 110 there through. In an open state (see Figure 3B), first plate closure 152a and second plate closure 152b are distanced from one another, said distance being higher than a predefined value.

In some embodiments, said distance is at least equal to or higher than the diameter of heating unit distal opening 222.

Advantageously, moving first 152a and second 152b plate closures towards one another to the close state can minimize heat loss from the internal space of heating unit 200 during a heating phase. However, since the natural tendency of heat is to move upwards, it is to be understood that locating such closure mechanism beneath heating unit distal opening 222, as exemplified in Figures 3A-3B, is merely optional. In some embodiments, apparatus 100 does not include first 152a and second 152b plate closures, along with first 156a and second 156b horizontal rods, leaving heating unit distal opening 222 constantly exposed to the external environment.

In some embodiments, the at least one heating unit opening comprises a single heating unit opening, configured to function both as heating unit proximal opening 212 and as heating unit distal opening 222. In such embodiments, leverage unit 102 is configured to drive elongated transport member 110 through the at least one heating unit opening into the heating unit internal shaft, and from the at least one heating unit opening, through a fluidized bed proximal opening, into a fluidized bed internal shaft ("fluidized bed proximal opening" and "fluidized bed internal shaft" to be further described herein below)..

In some embodiments, a heating unit 200 having a single heating unit opening, comprises at least one plate closure. In some embodiments, the at least one plate closure comprises a first plate closure 152a and a second plate closure 152b, located proximal to the at least one heating opening, such that all of the embodiments disclosed for first plate closure 152a and second plate closure 152b for a heating unit 200 having a heating unit proximal opening 212 and a heating unit distal portion 222, are applicable to a heating unit 200 having a single heating unit opening.

While first plate closure 152a and second plate closure 152b in the example depicted in Figures 3A-3B and described hereinabove, are configured to switch between an open state and a close state via closure rods facilitating movement of first plate closure 152a and second plate closure 152b either towards each other or away from one another, it will be clear to a person skilled in the art that other geometrical shapes and structure of plate closures, such as having a single plate configured to cover the entirety of the at least one heating unit opening, as well as other displacement mechanism, such as rotation motors and the like, can be utilized to enable an at least one plate closure to switch between an open state and a close state.

Reference is now made to Figures 4A-4C. Figures 4A and 4C constitute exploded views in perspective of fluidized bed reactor 300, from a top-side angle and from a bottom- side angle, respectively, in some embodiments. Figure 4B constitutes an exploded cross- sectional view in perspective of fluidized bed reactor 300, in some embodiments. Fluidized bed reactor 300 comprises freeboard 310. In some embodiments, fluidized bed reactor 300 further comprises gas distributor casing 340, plenum chamber 370, and distributor 700.

In some embodiments, fluidized bed reactor 300 further comprises mesh sieve holder 720, having a mesh sieve (not illustrated) with a plurality of apertures, configured to be large enough to allow gas flow there through, yet small enough not to allow powder to pass through. Distributor 700 comprises a plurality of apertures, configured to be large enough to allow gas flow there through. In some embodiments, the diameter of the apertures of distributor 700 is larger than the diameter of the mesh sieve. In some embodiments, the diameter of the apertures of distributor 700 is at least 3 millimeters.

The term "plurality", as used herein, means more than one.

Freeboard 310 comprises freeboard outer surface 312, freeboard inner surface 326, freeboard proximal lip 316, freeboard flange 320 rigidly connected to freeboard outer surface 312, freeboard inner seating 324 and freeboard distal extension 322.

In some embodiments, freeboard 310 further comprises door 314 connected to outer surface 312 by at least one hinge, such as hinges 318a and 318b. Door 314 is configured to allow lateral access, when opened, to a fluidized bed internal shaft (not numbered) confined by freeboard inner surface 326. Such access can be utilized, for example, allow access to placement section 140 of elongated transport member 110, for example for placement of article holder 800 thereon or removal of article holder therefrom 800 (placement section 140 and article holder 800 will be further described herein below). It is to be understood by a person skilled in the art, that other types of doors, hinges and window-mechanisms can be applied to freeboard 310 so as to allow access, for example to an operator's hand or to an external mechanical arm, to the internal space of freeboard 310.

In some embodiments, freeboard 310 is thermally insulated to reduce heat loss from the fluidized bed internal shaft. In some embodiments, freeboard 310 comprises a thermal- insulating cover to facilitate the thermal insulation of the fluidized bed internal shaft. In some embodiments, freeboard 310 is coated by a thermal-insulating coating to facilitate the thermal insulation of the fluidized bed internal shaft.

Fluidized bed reactor 300 is positioned adjacent to heating unit 200. Is some embodiments, fluidized bed reactor 300 is position distal to heating unit 200. In some embodiments, fluidized bed reactor 300 is positioned distal to heating unit 200 (see Figures 1A-1D), in a manner that freeboard proximal lip 316, surrounding at least one fluidized bed proximal opening (not numbered) of the fluidized bed internal shaft, is positioned distal to first 152a and second 152b plate closures at a predetermined distance. In some embodiments, the distance between proximal lip 316 and first 152a and second 152b plate closures is higher than 1 millimeter. In some embodiments, wherein apparatus 100 does not include first 152a and second 152b plate closures, freeboard proximal lip 316 is positioned distal to heating unit lower surface 220.

In some embodiments, fluidized bed reactor 300 is aligned with heating unit 200, such that the center of the perimeter set by freeboard proximal lip 316 coincides with at least one of heating unit proximal opening 212 and heating unit distal opening 222, configured to allow passage of at least elongated transport member 110 there through.

In some embodiments, fluidized bed reactor 300 is positioned adjacent to heating unit 200 such that the distance between freeboard proximal lip 316 and heating unit 200 is configured to allow access to placement section 140 of elongated transport member 110 when between fluidized bed reactor 300 and heating unit 200, for example for placement of article holder 800 thereon or removal of article holder therefrom 800 (embodiments not shown). In some embodiments, the distance between freeboard proximal lip 316 and heating unit 200 is configured to at least allow access to a human hand.

In some embodiments, fluidized bed reactor 300 further comprises at least one fluidized bed heat sensor. In some embodiments, the at least one fluidized bed heat sensor can be a thermocouple, thermometer, an IR sensor, or a thermistor. In some embodiments, dealloying apparatus 100 further comprises a thermally insulated access unit (not shown) between fluidized bed reactor 300 and heating unit 200, configured to allow access to placement section 140 of elongated transport member 110 embodiments not shown). In some embodiments, the access unit comprises an access unit door, similar to door 314, allowing lateral access to a placement unit internal shaft.

The terms "powder", "composition" and "fluidized composition", as used herein, are interchangeable.

Gas distributor casing 340 comprises casing intermediate outer surface 346, casing distal outer surface 350, casing intermediate inner surface 348, casing distal inner surface 352, casing proximal seating 354 located at the circumference of the proximal portion of casing intermediate inner surface 348, casing proximal flange 342 located at the circumference of the proximal portion of casing intermediate outer surface 346, casing distal seating 358 located between casing intermediate inner surface 348 and casing distal inner surface 352, casing distal flange 344 located between casing intermediate outer surface 346 and casing distal outer surface 350, and at least one casing inlet, such as casing inlets 356a, 356b, 356c and 356d, protruding through from casing distal outer surface 350 to casing distal inner surface 352.

Reference is now made to Figures 5a-5b. Figures 5A and 5B constitute a view in perspective and a cross-sectional view in perspective, respectively, of plenum chamber 370. Plenum chamber 370 comprises plenum chamber outer surface 374, plenum chamber inner surface 376, plenum chamber proximal flange 372 located at the circumference of the proximal portion of plenum chamber outer surface 374, plenum chamber inner extension 378 located at the circumference of the proximal portion of plenum chamber inner surface 376, plenum chamber distal flange 382 located at the circumference of the distal portion of plenum chamber outer surface 374, plenum chamber base 380, inlet tube outer fitting 384 protruding outwards from plenum chamber outer surface 374, configured to cover an inlet duct (not numbered) passing through inlet tube inner fitting 386 protruding inwards from plenum chamber inner surface 376.

In some embodiments, casing lower flange 344 comprises at least one aperture (not numbered), preferably a plurality of apertures. In some embodiments, plenum chamber proximal flange 372 comprises at least one aperture (not numbered), preferably a plurality of apertures. In some embodiments, the number of apertures in casing distal flange 344 matches the number of aperture in plenum chamber proximal flange 372. At least one aperture in casing distal flange 344 coincides with at least one aperture in plenum chamber proximal flange 372, in a manner that enables casing distal flange 344 to be attached to plenum chamber proximal flange 372, thereby connecting gas distributor casing 340 with plenum chamber 370.

Reference is now made to Figures 6A-6B. Figures 6A and 6B constitute a view in perspective and a cross-sectional view, respectively, of fluidized bed reactor 300 in its assembled form, in some embodiments. In the assembled form of fluidized bed reactor 300, freeboard flange 320 is attached to casing proximal flange 342 by aligning at least one of the apertures in freeboard flange 320 with at least one aperture in casing proximal flange 342, configured to allow passage of at least one bolt (not numbered) there through. Similarly, casing distal flange 344 is attached to plenum chamber proximal flange 372 by aligning at least one of the apertures in casing distal flange 344 with at least one aperture in plenum chamber proximal flange 372, configured to allow passage of at least one bolt (not numbered) there through. Freeboard distal extension 322 (see Figures 4B-4C) is positioned so as to coincide with at least a portion of casing intermediate inner surface 348. Distributor 700 rests on casing distal seating 358.

In some embodiments, Mesh sieve holder 720 rests on distributor 700. Mesh sieve holder 720 comprises mesh sieve holder outer surface 722, mesh sieve holder inner surface 724, mesh sieve depression 726 and a mesh sieve (not shown) attached to mesh sieve depression 726. In some embodiments, mesh sieve holder 720 further comprises a sponge (not shown) beneath the mesh sieve. Mesh sieve comprises a plurality of apertures, configured to be large enough to allow gas flow there through, yet small enough not to allow powder to pass through. In some embodiments, the dimensions of the plurality of apertures in mesh sieve holder 720 are smaller than the dimensions of the plurality of apertures in the distributor 700.

Casing distal outer surface 350, plenum chamber inner surface 376, plenum chamber inner extension 378 and plenum chamber base 380 together form a circumferential duct (not numbered), such that gas can flow from an external source through inlet tube outer fitting 384 and inlet tube inner extension 386 into said circumferential duct, and enter, through at least one casing inlet 356 into a plenum, defined as the space between casing lower inner surface 352, plenum chamber base 380 and distributor 700. Gas can then continue to flow from the plenum in the proximal direction through distributor 700 and mesh sieve holder 720, towards freeboard 310.

According to some embodiments, fluidized bed reactor 300 comprises gas inlet tube, configured to connect with a sidewall or the outer surface of fluidized bed reactor 300 (embodiments not shown).

Fluidized bed reactor 300 can be connected to base platform 130 (see Figures 1A-D) by at least one fluidized bed reactor attachment member (see 134a, 134b and 134c in figs 1A-D, 134d is hidden from view). Base platform 130 comprises slide members 136a and 136b, configured to slide along slide channels 138a and 138b of dealloying apparatus 100. In some embodiments, slide members 136a and 136b, configured to slide in the y direction along slide channels 138a and 138b of dealloying apparatus 100.

In some embodiments, base platform 130 further comprises base platform handle 132, configured to allow manual grip by an operator's hand to slide fluidized bed reactor base 130 back and forth in a direction perpendicular to the axial movement of elongated transport member 110, thereby enabling positioning of fluidized bed reactor 300 either in working position (see Figure 1 A), distal to heating unit 200, or in maintenance position (see Figure IB), wherein fluidized bed reactor 300 is offset from heating unit 200, allowing, for example, filling or removing powders, as well as disconnecting any parts of fluidized bed reactor 300 for maintenance operations.

In some embodiments, base platform 130 is configured to slide back and forth in the y-direction, thereby enabling positioning of fluidized bed reactor 300 either in working position beneath heating unit 200, or in maintenance position.

In some embodiments, fluidized bed reactor 300 further comprises at least one fluidized-bed heating element, configured to heat at least the internal space of fluidized bed reactor 300 to a predefined temperature. In some embodiments, at least one fluidized-bed heating element is configured to maintain heat within the internal space of fluidized bed reactor 300 at a substantially constant temperature.

The term "substantially constant temperature", as used herein, refers to a temperature fluctuating within ±10 degrees Celsius of a predefined value.

Reference is now made to Figures 7A-7C. Figures 7A and 7B constitute a cross- sectional view and a view in perspective, respectively, of fluidized bed reactor 300^a in its assembled form, in some embodiments. Figure 7C constitutes a partial cross-sectional view of a bottom section of fluidized bed reactor 300^a, in some embodiments. Fluidized bed reactor 300^a is differing from fluidized bed reactor 300 in that gas distributor casing 340, distributor 700 and mesh sieve casing 720 have been done away with, and in that plenum chamber 370 and freeboard 310 have been replaced with plenum chamber 370^a and freeboard 310 ^a, respectively. Freeboard 310^a comprises freeboard outer surface 312^a, freeboard inner surface 326^a, freeboard proximal lip 316^a, freeboard flange 320^a, freeboard inner seating 324^a and freeboard distal extension 322^a. In some embodiments, freeboard 310^a further comprises door 314^a connected to outer surface 312^a by at least one hinge, such as hinges 318^aa and 318^ab. Door 314^a is configured to allow lateral access, when opened, to the internal space of freeboard 310^a. It is to be understood by a person skilled in the art, that other types of doors, hinges and window-mechanisms can be applied to freeboard 310^a so as to allow access, for example to an operator's hand or to an external mechanical arm, to the internal space of freeboard 310^a.

In some embodiments, fluidized bed reactor 300^a is positioned distal to heating unit 200 (see Figures 1A-1D), in a manner that freeboard proximal lip 316^a is positioned distal to first 152a and second 152b plate closures at a predetermined distance. In some embodiments, the distance between proximal lip 316^a and first 152a and second 152b plate closures is higher than 1 millimeter.

In some embodiments, wherein apparatus 100 does not include first 152a and second 152b plate closures, freeboard proximal lip 316^a is positioned distal to heating unit distal surface 220.

In some embodiments, fluidized bed reactor 300^a is aligned with heating unit 200, such that the center of the perimeter set by freeboard upper lip 316^a coincides with at least one of heating unit proximal opening 212 and heating unit distal opening 222, configured to allow passage of at least elongated transport member 110 there through.

Plenum chamber 370^a comprises plenum chamber outer surface 374^a, plenum chamber inner surface 376^a, plenum chamber proximal flange 372^a located at the circumference of the proximal portion of plenum chamber outer surface 374^a, plenum chamber distal flange 382^a located at the circumference of the distal portion of plenum chamber outer surface 374^a, and plenum chamber base 380^a.

In some embodiments, freeboard flange 320^a comprises at least one aperture (not numbered), preferably a plurality of apertures. In some embodiments, plenum chamber upper flange 372^a comprises at least one aperture (not numbered), preferably a plurality of apertures. In some embodiments, the number of apertures in freeboard flange 320^a matches the number of apertures in plenum chamber upper flange 372^a. At least one aperture in freeboard flange 320^a coincides with at least one aperture in plenum chamber upper flange 372^a, in a manner that enables freeboard flange 320^a to be attached to plenum chamber upper flange 372^a, thereby connecting freeboard 310^a with plenum chamber 370^a.

While fluidized bed reactor 300^a is depicted in Figures 7A-7C as a cylindrical bed reactor, it is to be understood that the cross-sectional geometry of fluidized bed reactor 300^a is optionally different, such as a rectangular, elliptical, triangular or any other curvilinear or rectilinear cross-section.

Reference is now made to Figures 8A-8C. Figures 8A and 8B constitute views in perspective of freeboard flange 320^a with powder base plate 340^a, from a top-side angle and from a bottom-side angle, respectively, in some embodiments. Figure 8C constitutes a view in perspective of powder base plate 340^a with gas distribution unit 390^a configured to distribute gas flowing therethrough, in some embodiments. Gas distribution unit 390^a comprises at least one inlet tube fitting 360^a, through which gas can flow into gas distribution unit 390^a, and at least one nozzle body 364^a, through which gas can flow out of gas distribution unit 390^a. Powder base plate 340^a comprises at least one base plate aperture 368^a, through which the at least one nozzle body 364^a can pass and connect with at least one nozzle head 366^a. The at least one nozzle head 366^a can be connected with the end of the at least one nozzle body 364^a by any means known in the art, such as screwing, welding, and the like. Each nozzle head 366^a comprises at least one outlet orifice 330^a on its circumference, through which gas can flow into the inner space of freeboard 310^a.

In some embodiments, the diameter of powder base plate 340^a is equal to or lower than the inner diameter of freeboard 310^a, confined by freeboard inner surface 326^a.

While powder base plate 340^a is depicted in Figures 8A-8C as a circular plate, it is to be understood that the geometry of powder base plate 340^a is optionally different, such as a rectangular, elliptical, triangular or any other curvilinear or rectilinear cross-section.

In some embodiments, powder base plate 340^ais configured for placement within freeboard 310^a, such that the outer rim of powder base plate 340^arests on freeboard inner seating 324^a. In some embodiments, the outer rim of powder base plate 340^ais rigidly attached to freeboard inner seating 324^a.

Reference is now made to Figures 9-11B. Figure 9 constitutes a partial cross- sectional view of a distal section of fluidized bed reactor 300^b, in some embodiments. Figures 10A and 10B constitute a view in perspective and a cross-sectional view of nozzle 362^b, in some embodiments. Figures IOC and 10D constitute a view in perspective and a cross-sectional view of nozzle 362^c, in some embodiments. Figures 11 A and 1 IB constitute a view in perspective of powder base plate 340^b and powder base plate 340^d, respectively, in some embodiments. Fluidized bed reactor 300" is differing from fluidized bed reactor 300' in that gas distribution unit 390^a has been done away with, and in that plenum chamber 370^a, powder base plate 340^a and freeboard 310^a have been replaced with plenum chamber 370^b, powder base plate 370^b and freeboard 310^b, respectively. Freeboard 310^b (not shown in its entirety) comprises freeboard outer surface 312^b, freeboard inner surface 326^b, freeboard proximal lip 316^b (not shown), freeboard flange 320^b, freeboard inner seating 324^b and freeboard distal extension 322^b. In some embodiments, freeboard 310^b further comprises door 314^b (not shown) connected to outer surface 312^b by at least one hinge (not shown).

Plenum chamber 370^bcomprises plenum chamber outer surface 374^b, plenum chamber inner surface 376^b, plenum chamber proximal flange 372^b located at the circumference of the proximal portion of plenum chamber outer surface 374^b, plenum chamber distal flange 382^blocated at the circumference of the distal portion of plenum chamber outer surface 374^b, plenum chamber base 380^b, inlet tube outer fitting 384^bprotruding outwards from plenum chamber outer surface 374^b, configured to cover an inlet duct (not numbered) passing through inlet tube inner fitting 386^b, which is protruding inwards from plenum chamber inner surface 386^b.

Powder base plate 340^b comprises at least one base plate aperture 368^b, configured to accommodate at least one nozzle 362^b. Nozzle 362^b comprises nozzle body 364^b, nozzle head 366^b and at least one outlet orifice 330^b on the circumference of nozzle head 366^b, through which gas can flow into the inner space of freeboard 310^b. Figures 10A-10B depict an example of nozzle 362^b wherein the at least one outlet orifice 330^b is extending straightly, perpendicular to the axis of nozzle body 364^b. Figures 10C-10D depict another example of nozzle 362^c wherein the at least one outlet orifice 330^c is angled relative to the axis of nozzle body 364^c. As used herein, nozzle 362^c is interchangeable with nozzle 362^b in all embodiments throughout the specification. While Figures 10C-10D depict an embodiment of at least one outlet orifice 330^c being angled at an angle of 45° relative to the axis of nozzle body 364^c, it will be clear to a person skilled in the art than any other angle between at least one outlet orifice 330^c and the axis of nozzle body 364^c is optional.

While Figures 10A-10D depict embodiments of at least one outlet orifice 330^b, 330^c shaped as a straight channel, either perpendicular or angled relative to the axis of nozzle body 364^b, 364^c, it will be clear to a person skilled in the art than other shapes, such as tapering channels, winding channels and the likes, are optional.

In some embodiments, the diameter of powder base plate 340^b is equal to or lower than the inner diameter of freeboard 310^b, confined by freeboard inner surface 326^b.

In some embodiments, powder base plate 340^b is configured for placement within freeboard 310^b, such that the outer rim of powder base plate 340^b rests on freeboard inner seating 324^b.

In some embodiments, the outer rim of powder base plate 340^b is rigidly attached to freeboard inner seating 324^b.

Powder base plate 340^d comprises a different spatial arrangement of base plate apertures 368^d, configured to accommodate at least one nozzle 362^b.

In some embodiments, freeboard flange 320^b comprises at least one aperture (not numbered), preferably a plurality of apertures. In some embodiments, plenum chamber proximal flange 372^b comprises at least one aperture (not numbered), preferably a plurality of apertures. In some embodiments, the number of apertures in freeboard flange 320^b matches the number of apertures in plenum chamber proximal flange 372^b. At least one aperture in freeboard flange 320^bcoincides with at least one aperture in plenum chamber upper flange 372^b, in a manner that enables freeboard flange 320^b to be attached to plenum chamber proximal flange 372^b, thereby connecting freeboard 310^b with plenum chamber 370^b.

Reference is now made to Figures 12A-12E. Figures 12A and 12B constitute views a view in perspective and an exploded view in perspective of a fluidized bed reactor 300^e, respectively, according to some embodiments. Figures 12A and 12B constitute cross- sectional views in perspective taken on lines 12C-12C and 12D-12D of Figures 12A, respectively. Fluidized bed reactor 300^e is differing from fluidized bed reactor 300^a in that plenum chamber 370^a and powder base plate 340^a have been done away with. Fluidized bed reactor 300^e comprises freeboard 310^e and gas distribution unit 390^e.

While fluidized bed reactor 300^e is depicted in Figures 12A-12B as a rectangular bed reactor having four sidewalls (not numbered), it is to be understood that the cross-sectional geometry of fluidized bed reactor 300^e is optionally different, such as a circular, elliptical, triangular or any other curvilinear or rectilinear cross-section.

Freeboard 310^e comprises freeboard outer surface 312^e, freeboard inner surface 326^e, freeboard proximal lip 316^e and freeboard base 380^e. In some embodiments, freeboard 310^a further comprises a door 314^e connected to outer surface 312^e by at least one hinge, configured to function similarly to door 314 or 314^a (embodiments not shown).

In some embodiments, fluidized bed reactor 300^e is positioned distal to heating unit 200 (see Figures 1A-1D), in a manner that freeboard proximal lip 316^e is positioned distal to first 152a and second 152b plate closures at a predetermined distance. In some embodiments, the distance between proximal lip 316^e and first 152a and second 152b plate closures is higher than 1 millimeter.

In some embodiments, wherein apparatus 100 does not include first 152a and second 152b plate closures, freeboard proximal lip 316^e is positioned distal to heating unit distal surface 220.

In some embodiments, fluidized bed reactor 300^e is aligned with heating unit 200, such that the center of the perimeter set by freeboard upper lip 316^e coincides with at least one of heating unit proximal opening 212 and heating unit distal opening 222, configured to allow passage of at least elongated transport member 110 there through.

In some embodiments, gas distribution unit 390^e comprises at least one inlet tube fitting 360^e configured to adapt to at least one inlet tube (not numbered), at least one outer distribution tube 392^e, at least one intermediate tube 396^e, at least tube fitting 328^e and at least one inner distribution tube 394^e. While the example shown in Figures 12A-12B depicts a single inlet tube fitting 360^e configured to adapt to a single inlet tube (not numbered), two outer distribution tubes 392^e, five inner distribution tubes 394^e and a plurality of intermediate tubes 396^e and a plurality of tube fittings 328^e, it will be understood that the amount of each component may vary.

In some embodiments, inlet tube fitting 360^e is configured to receive at least an inlet tube or an additional adaptor connected to an inlet tube, and at least one of: outer distribution tube 392^e, intermediate tube 396^e, inner distribution tube 394^e or any combination thereof, so as to provide fluid connection between all components attached thereto. The example shown in Figures 12A-12B depicts a single inlet tube fitting 360^e adapted to connect with an inlet tube (not numbered) and two outer distribution tubes 392^e.

In some embodiments, tube fitting 328^e is configured to receive at least two of: outer distribution tube 392^e, intermediate tube 396^e, inner distribution tube 394^e or any combination thereof, so as to provide fluid connection between all components attached thereto.

In some embodiments, tube fitting 328^e may be shaped as a T-connector, such as tube fitting 328^ea (see Figure 12B). In some embodiments, tube fitting 328^e may be shaped as an L-connector, such as tube fitting 328^eb (see Figure 12B). In some embodiments, inlet tube fitting 360^e may be shaped as a T-connector (see Figure 12B). In some embodiments, inlet tube fitting 360^e may be shaped as an L-connector (embodiments not shown). In some embodiments, tube fitting 328^e or inlet tube fitting 360^e may be shaped according to any tube connectors known in the art.

The example shown in Figures 12A-12B depicts L-shaped tube fittings 328^eb adapted to connect with outer distribution tube 392^e and intermediate tube 396^e, or with intermediate tube 396^e and inner distribution tube 394^e. The example shown in Figures 12A- 12B depicts T-shaped tube fitting 328^ea adapted to connect with intermediate tubes 396^e and inner distribution tube 394^e.

Freeboard 310^e comprises at least one freeboard aperture 398^e. In some embodiments, freeboard comprises a plurality of freeboard aperture 398^e. In some embodiments, at least one freeboard aperture 398^e is configured in size and shape to receive inner distribution tube 394^e therethrough. In some embodiments, at least one freeboard aperture 398^e is configured in size and shape to receive at least a portion of at least one tube fittings 328^e, such that when at least one tube fittings 328^e is received within at least one freeboard aperture 398^e, at least one inner distribution tube 394^e may pass there through into the internal space of freeboard 310^e. According to some embodiments, at least one inner distribution tube 394^e is disposed within the internal space of freeboard 310^e. In some embodiments, at least one freeboard aperture 398^e is spaced proximal to freeboard base 380^e at a predefined distance. In some embodiments, at least one freeboard aperture 398^e is spaced at least 1 mm proximal to freeboard base 380^e. In some embodiments, at least one freeboard aperture 398^e is spaced at a maximal distance of 20 mm proximal to freeboard base 380^e.

Figures 12E and 12F constitute a bottom and cross-sectional views of one inner distribution tube 394^e, in some embodiments. Figure 12G constitutes a zoomed-in cross- sectional view of a portions of the fiuidized bed reactor depicted in Figure 12D. Inner distribution tube 394^e comprises at least one outlet orifice 330^e. In some embodiments, inner distribution tube 394^e comprises a plurality of outlet orifices 330^e along its length (see Figure 12E). In some embodiments, inner distribution tube 394^e comprises a plurality of evenly spaced outlet orifices 330^e distributed along its length (see Figure 12E).

In some embodiments, at least one cross-sectional region along the length of inner distribution tube 394^e comprises a plurality of outlet orifices 330^e (see Figure 12F). In some embodiments, a plurality of outlet orifices 330^e are angled along the cross-sectional circumference of inner distribution tube 394^e relative to each other. In the example of Figure 12F, two outlet orifices 330^e in the same cross-sectional region of inner distribution tube 394^e are angled at 90° relative to each other, each facing freeboard base 380^e. In some embodiments, a plurality of outlet orifices 330^e are angled at angles intended to cover a larger portion of freeboard base 380^e when gas flows there through.

In some embodiments, at least one inner distribution tube 394^e abuts against freeboard base 380^e. In some embodiments, at least one inner distribution tube 394^e is spaced proximal to freeboard base 380^e at a predefined distance. In some embodiments, at least one inner distribution tube 394^e is spaced at least 1 mm proximal to freeboard base 380^e. In some embodiments, at least one inner distribution tube 394^e is spaced at a maximal distance of 20 mm proximal to freeboard base 380^e.

In some embodiments, at least one outlet orifices 330^e is positioned along inner distribution tube 394^e so as to not be blocked by freeboard base 380^e when gas flows there through. In some embodiments, at least one outlet orifices 330^e is positioned along inner distribution tube 394^e so as to be spaced relative to freeboard base 380^e. In some embodiments, at least one outlet orifices 330^e is positioned along inner distribution tube 394^e such that gas direction when gas flows there through is angled relative to freeboard base 380^e.

In some embodiments, at least two components selected from: at least one inlet tube fitting 360^e, at least one outer distribution tube 392^e, at least one intermediate tube 396^e, at least tube fitting 328^e and at least one inner distribution tube 394^e, are separate components configured to be attached to each other. In some embodiments, at least two components selected from: at least one inlet tube fitting 360^e, at least one outer distribution tube 392^e, at least one intermediate tube 396^e, at least tube fitting 328^e and at least one inner distribution tube 394^e, are integrally formed.

Reference is now made to Figures 13A-13B. Figures 13A and 13B constitute views in perspective of article holder 800 prior to and post placement on placement section 140 of elongated transport member 110, respectively, in some embodiments. Article holder 800 comprises holder slot 802 and at least one holder aperture 804. In some embodiments, article holder 800 comprises a plurality of holder apertures 804 located circumferentially at a predefined distance from the outer edge (not numbered) of article holder 800. The at least one holder aperture 804 is configured for insertion of at least one hook 810 therein, said hook 810 is configured for holding an article, such as an article of jewelry.

The terms "article of jewelry", "jewelry item" and "item of jewelry" are interchangeable, and refer to common jewelry items such as a necklace, an earring, a bracelet, a ring, a charm, a chain and the like.

Elongated transport member 110 comprises placement section 140 configured to accommodate article holder 800, adjacent to transport member distal end 142. In some embodiments, transport member distal end 142 is formed as a placement base extension, wherein the circumference of transport member distal end 142 extends beyond the circumference of placement section 140.

In some embodiments, placement section 140 is configured in its geometry and dimensions to match holder slot 802, such that when holder slot 802 slides along placement section 140, article holder 800 can be supported by the outer edge (not numbered) of transport member distal end 142, being supported thereby. When article holder 800 is placed on and abuts against transport member distal end 142, movement of elongated transport member 110 in the distal and proximal directions results in movement of article holder 800 in the same directions, along with any articles that can be placed on the at least one hook 810.

In some embodiments, when article holder 800 is placed on transport member distal end 142, vertical movement of elongated transport member 110 along the z-direction results in vertical movement of article holder 800, along with any articles that can be placed on the at least one hook 810, in the same direction.

Reference is now made to Figures 14A-16B. Figures 14A and 14B constitute views in perspective of a dealloying apparatus 100, with a washing unit 900 located offset from heating unit 200 and distally to a heating unit 200, respectively, in some embodiments. Figure 15 constitute a cross-sectional view in perspective of dealloying apparatus 100 with washing unit 900. Figure 16 constitutes a partial view in perspective of washing unit 900 adjacent to fiuidized bed reactor 300.

In some embodiments, dealloying apparatus 100 further comprises washing unit 900, configured to enable placement of article holder 800, along with any articles that can be placed on the at least one hook 810, therein, for washing the articles. Washing unit 900 comprises washing unit outer surface 912 having washing unit proximal lip 916, and washing unit base 980.

In some embodiments, washing unit 900 further comprises a door or a window- mechanisms connected to washing unit outer surface 912 by at least one hinge or other attachment means, configured to allow lateral access, for example to an operator's hand or to an external mechanical arm, to the internal space of washing unit 900 (embodiment not shown).

Washing unit 900 can be connected to base platform 130 adjacent to fiuidized bed reactor 300 (see Figures 14A-16). Displacement of base platform 130 back and forth in a direction perpendicular to the axial movement of elongated transport member 110 is configured to enable positioning of washing unit 900 in washing position (see Figures 14B- 16), distal to heating unit 200, or in stand-by position (see fig la), wherein washing unit 900 is offset from heating unit 200.

In some embodiments, base platform 130 is configured to slide back and forth in the y-direction, thereby enabling positioning of washing unit 900 either in washing position beneath heating unit 200, or in stand-by position.

In some embodiments, dealloying apparatus 100 further comprises a base platform motion unit (not shown), configured to facilitate automatic displacement of base platform 130 between at least two optional positions, for example to place either fiuidized bed reactor 300 or washing unit 900 in a position to receive elongated transport member 110 therein. In some embodiments, washing unit 900 is configured to include washing gas or liquid, such as water. In some embodiments, washing unit 900 is configured to include at least one washing agent. In some embodiments, washing unit 900 comprises means for facilitating washing of articles placed therein, such as facets, sprinklers, brushes and the like (embodiments not shown).

In some embodiments, washing unit 900 is configured to allow access to its internal space through at least one washing unit proximal opening (not numbered) confined by washing unit proximal lip 916, as depicted in Figures 14A-16. In some embodiments, washing unit 900 is configured to allow access to its internal space through a lateral opening (embodiments not shown).

Reference is now made to Figures 17A-17F. Figures 17A, 17B, 17C, 17D, 17E and 17F constitute partial views of dealloying apparatus 100 during phases I- VI of a method for powder covering articles, respectively, in some embodiments. Phase I shown in Figure 17A exhibits a starting configuration of dealloying apparatus 100, wherein door 314 of fiuidized bed reactor 300 is closed.

Phase II shown in Figure 17B exhibits a configuration in which door 314 of fiuidized bed reactor 300 is opened, exposing elongated transport member 110 which is positioned so that placement section 140 and transport member distal end 142 are at level along the axis of movement of elongated transport member 110, distal to heating unit 200 and visible through the opening exposed by door 314.

In some embodiments, elongated transport member 110 is positioned in Phase II, as depicted in Figure 17B, a height level, along the z-directions, lower than heating unit 200.

Phase III shown in Figure 17C shows article holder 800 as it is approximated to placement section 140 through the opening of door 314.

Phase IV shown in Figure 17D shows article holder 800 placed in placement section

140, resting on transport member distal end 142. After such placement, in some embodiments, door 142 is closed (not shown in Figure 17D) and first 152a and second 152b plate closures are displaced apart from one another (similar to the configuration of Figure 3B) to allow movement of article holder 800 from fiuidized bed reactor 300 to heating unit 200.

Phase V shown in Figure 17E exhibits a configuration in which elongated transport member 110, in some embodiments, is displaced in a proximal direction to a level, such that article holder 800, along with any articles (not shown) that can be placed on hooks 810, is located in its entirety within heating unit 200. First 152a and second 152b plate closures are displaced to be in contact with each another to prevent heat loss from heating unit 200 (similar to the configuration of Figure 3 A), as first heating step initiates, during which heat is generated in heating unit 200 to allow heating of articles (not shown) that can be placed on hooks 810. In some embodiments, displacement of first 152a and second 152b plate closures occurs simultaneously at approximately the same rate and for approximately the same distance. In some embodiments, heat is generated within heating unit 200 to reach at least the first temperature, as defined hereinabove. In some embodiments, heating lasts for a predefined time period tl , after which first 152a and second 152b plate closures are displaced apart from one another (similar to the configuration of Figure 3B) to allow movement of article holder 800 from heating unit 200 to fluidized bed reactor 300.

The term "approximately the same", as used herein, refers to values being in the range of ±10% from one another.

In some embodiments, at least one motion unit heat sensor (not shown), is located in vicinity of either distal section of elongated transport member 110 or article holder 800, said motion unit heat sensor location is adapted so as to be able to measure temperatures of or in the vicinity of articles that can be placed on hooks 810. In some embodiments, the at least one motion unit heat sensor comprises either one of: a thermocouple, a thermometer, an IR sensor, or a thermistor that is operable at least in the range temperatures of heating unit 200.

In some embodiments, a predefined first temperature threshold is defined, such that when temperature measured by the at least one heating unit heat sensor or the at least one motion unit heat sensor, reaches said first temperature threshold, first 152a and second 152b plate closures are displaced apart from one another (similar to the configuration of Figure 3b) to allow movement of article holder 800 from heating unit 200 to fluidized bed reactor 300.

Phase VI shown in Figure 17F exhibits a configuration in which a process of fluidization of powder placed within fluidized bed reactor 300 is initiated, and elongated transport member 110 is displaced distally to a level, such that article holder 800, along with any articles (not shown) that can be placed on hooks 810, is immersed in its entirety within the fluidized powder (not shown) contained in fluidized bed reactor 300. In some embodiments, article holder 800 remains in fluidized bed reactor 300 for a predefined time period t2.

In some embodiments, a second temperature threshold is defined such that article holder 800 remains in fluidized bed reactor 300 until the temperature measured by the at least one fluidized bed heat sensor or the at least one motion unit heat sensor, reaches said second temperature threshold. In some embodiments, second temperature threshold is lower than first temperature threshold.

In some embodiments, fluidized bed reactor 300 comprises at least one fluidized composition level sensor. In some embodiments, fluidized bed reactor 300 comprises at least one fluidized composition consumption sensor. In some embodiments, the at least one fluidized composition level sensor is indicative of fluidized composition consumption. In some embodiments, the at least one fluidized composition consumption sensor is separate from the at least one fluidized composition level sensor, based on other indicative parameters, such as powder weight.

In some embodiments, threshold values set for either fluidized composition level sensor or fluidized composition consumption level are used to whether the amount of powder in the fluidized bed reactor 300 needs to be adjusted. In some embodiments, threshold values set for either fluidized composition level sensor or fluidized composition consumption level are used to define the time period during which article holder 800 remains in fluidized bed reactor 300.

In some embodiments, the method further comprises of phase VII, similar in its configuration to the configuration of Figure 17E, in which main rod 110 is displaced proximally to a level, such that article holder 800 is positioned at a level essentially equal to its level in phase V. First 152a and second 152b plate closures are displaced to be in contact with one another to prevent heat loss from heating unit 200 (similar to the configuration of Figure 3A), and second heating step initiates, during which heating unit 200 is generating heat for either a predefined time period or to reach at least the second temperature threshold, as defined hereinabove.

In some embodiments, the heat generated by heating unit 200 in phase VII is essentially equal to the heat generated by heating unit 200 in phase V.

The term "essentially equal", as used herein, refers to values being in the range of ±10% from one another. In some embodiments, heating lasts for a predefined time period t3, after which first 152a and second 152b plate closures are displaced away from each another (similar to the configuration of Figure 3B) to allow movement of article holder 800 from heating unit 200 to fluidized bed reactors 300.

In some embodiments, a third temperature threshold is defined such that heating lasts until the at least one heating unit heat sensor or the at least one motion unit heat sensor, reaches the third temperature threshold. In some embodiments, the third temperature threshold is essentially equal to the first temperature threshold. In some embodiments, the third temperature threshold is different from either the first temperature threshold or the second temperature threshold.

A final phase of the method, in some embodiments, comprises the step of displacing elongated transport member 110 either proximally (if final phase occurs right after phase VI) or distally (if final phase occurs right after phase VII), such that article holder 800 is placed at a level essentially equal to its level in phase IV (similar to the configuration in Figure 17D). In some embodiments, article holder 800 is removed from placement section 140 when positioned outside of fluidized bed reactor 300. In some embodiments, article holder 800 is removed from placement section 140 when positioned inside the placement unit. In some embodiments, either the door of the placement unit or door 314 can be opened, thereby allowing access for the removal of article holder 800 from placement section 140 (similar to the configuration in Figure 17E).

In some embodiments, phase IV is followed directly by phase VI, thereby skipping the displacement of article holder 800 to heating unit 200 and heating the articles that can be placed on hooks 810 prior to initiation of fluidization. In some embodiments, employing a method of initiating the fluidization of phase IV without the heating of phase V, necessitates execution of phase VII as described hereinabove.

In some embodiments, the method is followed by an additional step of washing (see Figures 15-16), such that if placement section 140 of elongated transport member 110 is at a level within fluidized bed reactors 300, it is displaced distally such that lateral movement of fluidized bed reactors 300 will not interfere with elongated transport member 110. Washing unit 900 is displaced, for example via displacement of base platform 130, to a washing state, such that washing unit 900 is aligned and potentially concentric with elongated transport member 110. This is followed by displacement of elongated transport member 110 in the distal direction, that article holder 800 is placed at a level within the internal space of washing unit 900, thereby enabling washing of the articles held by article holder 800 therein.

Reference is now made to Figure 18. Figure 18 constitutes a block diagram of functional components of dealloying apparatus 100, in some embodiments. Dealloying apparatus 100 comprises a microcontroller 1430, configured to control the operations of leverage unit 1440, heating unit 1450 and fiuidized bed reactor 1460. In some embodiments, microcontroller 1430 is further configured to control the operations of washing unit 1470. In some embodiments, microcontroller 1430 is further configured to control the operations of base platform 1480. In some embodiments, microcontroller 1430 is further configured to control the operations of a camera (not shown).

In some embodiments, leverage unit 1440 is similar in function and connectivity to leverage unit 116. In some embodiments, heating unit 1450 is similar in function and connectivity to heating unit 200. In some embodiments, fiuidized bed reactor 1460 is similar in function and connectivity to either one of fiuidized bed reactors 300, 300^a, 300^b, 300^c, 300° or 300^e. In some embodiments, washing unit 1470 is similar in function and connectivity to washing unit 900. In some embodiments, base platform 1480 is similar in function and connectivity to base platform 130.

Microcontroller 1430 may be configured with a processing unit and a memory (not shown). The processing unit may be a single or multi-core processor, which may be general purpose or specifically adapted for use in dealloying apparatus 100. The memory of the processor may be volatile or non- volatile memory or a combination thereof.

In some embodiments, microcontroller 1430 can be programmed with specific instructions by an operator 1410, through a user interface 1420. In some embodiments, operator 1410 can control the functionality of microcontroller 1430 in real-time through user interface 1420 and receive feedback regarding functionality of microcontroller 1430 and inputs received by microcontroller 1430 from at least one of: leverage unit 1440, heating unit 1450 and fiuidized bed reactor 1460 through user interface 1420. In some embodiments, operator 1410 can further control the functionality of microcontroller 1430 in real-time through user interface 1420 and receive feedback regarding functionality of microcontroller 1430 and inputs received by microcontroller 1430 from any of: washing unit 1470, base platform 1480 and the camera. As used herein, the term "user interface" refers to an interface that enables information to be passed between a human user (such as operator 1410) and hardware or software components (such as microcontroller 1430).

In some embodiments, operations of leverage unit 1440 controlled by microcontroller 1430 comprise at least one of: positioning, acceleration and speed of leverage unit 1440, wherein positioning affects distal and proximal displacement of elongated transport member 110. In some embodiments, positioning affects vertical displacement of elongated transport member 110 along the z axis.

In some embodiments, either one of positioning and speed of leverage unit 1440 can be manually controlled by operator 1410.

In some embodiments, at least one of position and speed of leverage unit 1440 is transmitted in real-time to microcontroller 1430, which can affect follow-up commands sent by microcontroller 1430 to leverage unit 1440, as well as be reflected on user interface 1420.

In some embodiments, leverage unit 1440 comprises at least one motion unit heat sensor (not shown). In some embodiments, at least one motion unit heat sensor is located in the vicinity of placement section 140. In some embodiments, the at least one motion unit heat sensor can be a thermocouple, a thermometer, an IR sensor, or a thermistor. In some embodiments, data read by the at least one motion unit heat sensor can be transmitted in realtime to microcontroller 1430, which can affect follow-up commands sent by microcontroller 1430 to leverage unit 1440, as well as be reflected on user interface 1420.

In some embodiments, dealloying apparatus 100 further comprises at least one camera (not shown), configured to monitor at least one performance of at least one component of dealloying apparatus 100. In some embodiments, microcontroller 1430 is configured to receive inputs from the camera and adjust performance of at least one component of dealloying apparatus 100 according to the received input.

In some embodiments, operations of heating unit 1450 controlled by microcontroller 1430 comprise at least one of: displacement of first 152a and second 152b plate closures, away from one another or towards each other, representing an open (similar to the configuration in Figure 3B) or close (similar to the configuration in Figure 3A) state, respectively, and temperature control, i.e. heat generation, of heating unit 1450. In some embodiments, heating unit 1450 comprises at least one heating unit heat sensor. In some embodiments, the at least one heating unit heat sensor can be a thermocouple, thermometer, an IR sensor, or a thermistor. In some embodiments, fluidized bed reactor 1460 comprises at least one fluidized bed heat sensor (not shown). In some embodiments, the at least one fluidized bed heat sensor can be a thermocouple, thermometer, an IR sensor, or a thermistor. In some embodiments, data read by the at least one heating unit heat sensor, the at least one fluidized bed heat sensor, or the at least one motion unit heat sensor, can be transmitted in real-time to microcontroller 1430, which can affect follow-up commands sent by microcontroller 1430 to heating unit 1450, as well as be reflected on user interface 1420.

In some embodiments, operations of fluidized bed reactor 1460 controlled by microcontroller 1430 comprise at least one of: activation and deactivation of fluidized bed reactor 1460, and control of gas flow through gas flow inlet (not shown) into fluidized bed reactor 1460. In some embodiments, fluidized bed reactor 1430 comprises at least one fluidized composition level sensor (not shown). In some embodiments, fluidized bed reactor 1430 comprises at least one fluidized composition consumption sensor. In some embodiments, the at least one fluidized composition level sensor is indicative of fluidized composition consumption. In some embodiments, the at least one fluidized composition consumption sensor is separate from the at least one fluidized composition level sensor, based on other indicative parameters, such as powder weight. In some embodiments, data read by the at least one fluidized composition level sensor or the at least one fluidized composition consumption sensor, can be transmitted in real-time to microcontroller 1430, which can affect follow-up commands sent by microcontroller 1430 to fluidized bed reactor 1460, as well as be reflected on user interface 1420.

In some embodiments, operations of base platform 1480 controlled by microcontroller 1430 comprise at least an automatic displacement of the base platform 1480, so as to place either fluidized bed reactor 1460 or washing unit 1470 in alignment with leverage unit 1440.

In some embodiments, operations of washing unit 1470 controlled by microcontroller 1430 comprise at least activation and deactivation of washing unit 1470. In some embodiments, washing unit 1470 comprises at least one liquid level sensor (not shown). In some embodiments, data read by the at least one liquid level sensor can be transmitted in real-time to microcontroller 1430, which can affect follow-up commands sent by microcontroller 1430 to washing unit 1470 or base platform 1480, as well as be reflected on user interface 1420.1n some embodiments, operator 1410 can select a representative parameter in user interface 1420, said representative parameter being a parameter set with predefined values for at least one of the operations of any of: leverage unit 1440, heating unit 1450, fluidized bed reactor 1460 or any combination thereof. In some embodiments, a representative parameter having a set of predefined values for specific operation as described hereinabove, represents a desired outcome for articles placed in dealloying apparatus 100. For example, a representative parameter can be a desired hue or color for a specific type of jewelry placed in dealloying apparatus 100.

In some embodiments, dealloying apparatus 100 is devoid of microcontroller 1430, such that at least some of the functions performed by microcontroller 1430 as disclosed hereinabove can be performed manually by an operator.

The following examples are presented in order to more fully illustrate some embodiments, of the invention. They should, in no way be construed, however, as limiting the broad scope of the invention.

EXAMPLES

Example 1: General gilding process and color measurement

A "K" Karat yellow gold alloy in the form of a disc having 19mm diameter and 0.8mm thickness, at least one side polished, was inserted into a device as described above containing a composition of powdered nitrate and ammonium salts. The gold alloy disc had a hole, such that it can be hooked on a holder. The heating unit was pre-set to a predefined temperature, which is also referred as 'predefined first temperature threshold'. The gold alloy was placed on the holder then heated in the oven until reaching a temperature, which is referred as 'first temperature'. When reaching the first temperature, the holder together with the sample were immediately moved to the fluidized composition of NH₄CI and KNO₃ in the fluidized bed reactor module. The sample remained in the fluidized composition for a period of time referred as 'Predefined time period t2' and then moved to the oven for 'predefined time period t3'. After predefined time period t3 in the oven, the holder with the sample were moved to the washing unit for immediate washing for predefined time period t4. After predefined time period t4 in the washing unit, the holder with the sample were moved to home position.

Thereafter, the sample was detached from the holder and washed with tap water. Then the sample was entered into a rotary tumbler containing highly polished stainless steel balls, water and soap for about 1 minute. The samples were measured using an x-rite Q60 spectrophotometer under D65 illumination (daylight illumination), in SPIN mode (including the specular component of the measurement) and in 10° observer mode (represents the human chromatic response across the visible spectrum) and were evaluated for gold enrichment of the surface through examination of their color distance from the target color. The distance between two colors is a metric measure in color science. It allows quantified examination of color differences. Common definitions make use of the Euclidean distance in a device independent color space. The distance is calculated as:

where L*, a* and b* indicate color parameters in the L*a*b* color space; 'L' for lightness and 'a' and 'b' for the color opponents green-red and blue-yellow, respectively, and where the subscripts 'alloy' and 'target' indicate the measured alloy and target color respectively. The smaller the ΔΕ (distance from target color, e.g. from the color corresponding to 24K gold), the closest the sample to target color.

Example 2: Detailed parameters and color maps

The above described process was employed on several gold alloy discs, each having a karat value of either 21K, 18K or 14K, while varying the process parameters through the device interface as depicted in Table 1 for 21K gold alloys, Table 2 for 18K gold alloys and Table 3 for 14K gold alloys. Varying the process parameters resulted in different hues for each kind of alloy as represented in Figures 19-21 and Tables 1-3.

Table 1 : depletion gilding of 21K gold alloy

[1] not considering L* Table 2: depletion gilding of 18K gold alloy

[1] not considering L^:

Table 3: depletion gilding of 14K gold alloy

[1] not considering L^:

As seen in Tables 1-3 and in Figures 19-21 , the process yields high gilding of gold alloys having various fineness levels. Specifically, the significantly lower levels of distance from pure gold witnessed for the gilded alloys indicate that they have similar visible properties compared to pure gold. Moreover, even the relatively low fineness 14K alloy was able to get closer to pure gold color after the process, which indicates that alloys having lower karat values are good candidates for gilding that provides sufficient results.

Example 3: Color decay of the gilded alloys in response to abrasion

In order to evaluate the surface quality of the alloys after depletion gilding process, gilded alloys were subjected to an abrasion test. The test compared the depletion gilding technology (trend line marked in circles) with the standard competing technology of gold electroplating (trend line marked in squares). The alloys gilded by the depletion gilding technology were prepared according the process of Example 1 and the specifications in Table 1, referring to alloys #1 , #2 and #3.

In the test, a gilded alloy was abraded using porcelain stones rotating with the sample in a rotary tumbler and monitored for its color decay as a function of abrasion time. Figure 21 is a graph depicting the alloy color degradation as a function of abrasion time in rotary tumbler with porcelain stones. The X axis indicates the abrasion time while the Y axis represent the normalized color distance from color after gilding. For example, the value of 0.5 on Y axis indicates 50% decay in color from the starting point which is the gilded sample.

As can be seen in Figure 21 in both technologies color is decaying due to the abrasion as a function of its time. Further, the rate of color decay is comparable, with a small advantage to the depletion gilding technology, in the time period starting in 50 minutes and ending in 250 minutes. It is concluded that the color stability toward abrasion of gold products gilded as above is at least in the level of quality of other gold alloys, which are approved for jewelry.

Example 4: Gilding durability of the gilded alloys

In order to evaluate the durability of the alloys after depletion gilding process, 18K and 21 K alloys were gilded as in Example 1. The 21 K alloys were gilded according to the specifications in Table 1, referring to alloys #1, #2 and #3; and The 18K alloys were gilded according to the specifications in Table 2, referring to alloys #1 , #2, #3 and #4. Samples were maintained up to 354 days in laboratory environment having 50-70% relative humidity. Table 4 presents the color change of gilded alloys over time.

Table 4: color changes in gilded alloys

distance compared to the color right after gilding

As can be seen in Table 4 color is very slowly decaying as a function of time. Further, even after prolonged periods (almost one year), the color is substantially maintained at a very low distance compared to the freshly gilded sample. Example 5: Tarnish resistance tests

In order to evaluate the tarnish resistance of the gilded alloys, a 14K gold alloy and an 18K gold alloy were gilded as described in Examples 1 and 2. The test compared the alloys gilded according to the depletion gilding technology of Example 1 with alloys, which underwent gold electroplating.

Both electroplated, depletion gilded and reference untreated alloys were hanged over an aqueous solution containing 2% ammonium sulfide. The solution was then heated to 60°C and the alloys were maintained in the corrosive environment for 45 minutes.

Figures 23A-F show the resulting alloys after the tarnish test. Figure 23 A is a photograph of a 14K non-gilded alloy after the exposure to ammonium sulfide. Figure 23B is a photograph of an electroplated 14K alloy after the exposure to ammonium sulfide. Figure 23C is a photograph of a 14K alloy, which underwent the process of Example 1, after the exposure to ammonium sulfide. Figure 23D is a photograph of a 18K non-gilded alloy after the exposure to ammonium sulfide. Figure 23E is a photograph of an electroplated 18K alloy after the exposure to ammonium sulfide. Figure 23F is a photograph of a 18K alloy, which underwent the process of Example 1, after the exposure to ammonium sulfide.

Figures 23A-23F indicate that alloys treated according to the process of Example 1 were not affected by the corrosive ammonium sulfide environment, unlike the electroplated alloys that showed discoloration at some areas over the alloy surface.

Example 6: Surface element concentration of the gilded alloys

In order to evaluate the gold enrichment in the gilded alloys, a gold alloy gilded according to the procedure described in Example 1, according to the specifications depicted in Table 1, was examined using the In-depth XPS technique. This technique gradually sputters a material and measures the concentration of elements as a function of the sputtering cycle of the examined material. The sputtering cycle is in correlation with the depth of the material, as each cycle penetrates deeper therein. In general, efficiently gilded alloys should present higher concentration of gold in the outer layer of the material than in its inner layers. In this case, the gold concentration should be decreased when penetrating towards the bulk until reaching the original gold concentration of the alloy. The results are graphically presented in Figure 24A, which depicts gold percentage vs. sputtering cycle; Figure 24B, which depicts copper percentage vs. sputtering cycle; and Figure 24C, which depicts silver percentage vs. sputtering cycle. Generally, the elemental composition of the surface is examined starting with the outermost layer, penetrating until reaching up to 50nm into the alloy.

Indeed, as can be seen in Figure 24A, the outmost layer of the gilded alloy is highly enriched in gold (about 96% w/w), whereas upon the sputtering of the alloy into more inner layers, the relative proportion of gold was reduced. Consequently, after 15-20 sputtering cycles the gold concentration in inner layers of the gold alloy stabilized at about 87-88% w/w, which is the original proportion of gold in 21K golden alloys. Conversely, the proportion of the base metal, copper, was increased upon penetrating deeper layers of the alloys (Figure 24B). This indicates that copper is removed in the process described herein from the surface of gold alloys, but not from core layers, thereby allowing integrity of the alloy's core. Specifically, the XPS measurements show that the gold-enriched outer layer of the alloy contains only 3% w/w copper and after 10-15 sputtering cycles the copper concentration in inner layers of the gold alloy stabilizes at about 10% w/w, which is the original proportion of copper in the 2 IK alloy that has been used. Interestingly, the measured proportion of silver was generally constant in the range of 0.015 - 0.02 (i.e. 1.5% - 2% w/w) in different layers of the alloy. This phenomenon may be explained by the relative inertness of silver to chemical corrosion, which is higher than that of copper, but still lower than that of gold.

Example 7: Depletion gilding of gold coins to various colors

The process described in Example 1 was employed on several similar 18K gold coins, while varying the process parameters through the device interface. Varying the process parameters resulted in different hues for each kind of coin as represented in Figure 25. The results indicate the changing the parameters of the process yields high gilding of coins having various fineness levels. Specifically, copies of the original untreated 18K gold coin were subjected to the process of Example 1, under different conditions, leading to four gilded coins, each having a different color. Specifically, the measured color distances of the four gilded coins form the original untreated coin were: 7.72, 15.84, 16.16 and 21.33, based on the process specifications.

One of the coins, which was the closest to pure gold, had color parameters of L*=81.24 a*= 10.74 b*=38.52, the significant distance of the treated coin indicates that it has similar visible properties compared to pure gold. The various distances from the original coins, as shown above, are showing that varying process parameters can lead to different colors, between that of pure gold and that of 18K gold.

Example 8: Depletion gilding of gold alloys having different compositions

The process described in Example 1 was employed on four 9K gold alloys having different compositions. Each of the alloys consists of about 37.5% gold and 62.5% base metal compositions, where the base metal compositions include zinc, silver and copper in different proportions. The commercial names and base metal compositions of the alloys are specified in Table 5.

Table 5: base metal compositions of commercial 9K gold alloys

After undergoing the process according to Example 1 , the four different alloys were enriched in gold, thus approaching the target of 18K color. The starting and end colors and process parameters are shown in Table 6.

Table 6: de letion gilding of 9K gold alloys

g e In order to evaluate the gold enrichment in the gilded alloys, the gilded OG130A gold alloy presented in Table 6 was examined in the In-depth XPS technique as described in Example 6. The results are graphically presented in Figure 26A, which depicts gold percentage vs. sputtering cycle; Figure 26B, which depicts copper percentage vs. sputtering cycle; Figure 26C, which depicts zinc percentage vs. sputtering cycle; and Figure 26D, which depicts silver percentage vs. sputtering cycle. Generally, the elemental composition of the surface was examined starting with the outermost layer, penetrating until reaching up to 50nm into the alloy.

Again, as can be seen in Figure 26A, the outmost layer of the gilded alloy is enriched in gold (about 75-80% w/w), whereas upon the sputtering of the alloy into more inner layers, the relative proportion of gold is reduced. Consequently, after 6-15 sputtering cycles the gold concentration in inner layers of the gold alloy stabilized at about 40% w/w, which is close to the percentage of gold in 9K golden alloys.

Conversely, the weight percentages of the base metals, copper and zinc, were increased upon penetrating deeper layers of the alloys (Figure 26B and Figure 26C). This indicates that copper and zinc are removed in the process described herein from the surface of gold alloys, but not from core layers. This trend is more pronounce with the more reactive zinc. Specifically, the XPS measurements show that the gold-enriched outer layer of the alloy contains only 10% w/w copper and no detectable amount of zinc. After 4-15 sputtering cycles the copper concentration in inner layers of the gold alloy stabilizes at about 50% w/w and the zinc concentration at about 5-6%. The measured proportion of silver was reduced upon sputtering from 12% in the external layer to about 4% in the inner layers. This may be explained by the relative inertness of silver to chemical corrosion, which is higher than that of copper and zinc, which constitute the majority of mass in the examined 9K alloy. In conclusion, 9K alloys, which are relatively gold poor were gilded to form alloys which resemble 18K gold alloy both visibly (distance < 2) and in composition (>75%) in their outer layer. The process is shown to be compatible with practically any base metal, commonly used in the yellow gold jewelry industry.

Example 9: Depletion gilding of different forms of gold alloys

It was also of interest to see whether the depletion gilding process is suitable for gilding stamped coins and jewelry items having common structural constraints. Example 9A: Two standard bullion coins were subjected to a depletion gilding process. The coins after gilding are presented in Figure 27. It is seen that two goals were achieved: first, the surface of the gold coins became substantially gilded; and second, the stamping on the coins was maintained without any visible damages or alterations. Example 9B: A gold ring having a rough surface and groves of about 0.5mm was subjected to a depletion gilding process. Generally, it is a challenge to efficiently gild objects having rough surfaces, such as this type of rings. It is a further challenge to successfully gild object having grooves using electrochemical plating, as it tends to result in non-uniform plating. The ring after gilding is presented in Figure 28. It is seen that the goal of successful uniform plating was achieved.

Example 9C: A gold ring having cubic zirconia gemstones was subjected to a depletion gilding process. The ring after gilding is presented in Figure 29. It is seen that two goals were achieved: first, the surface of the gold ring became substantially gilded; and second, the gemstone was maintained without any visibly damages or alterations. Example 9D: A gold plate was subjected to a depletion gilding process. The plate after gilding is presented in Figure 30. Again, it is seen that the goal of successful gilding was achieved, such that there are no visible differences between the gilded plate and a pure gold plate.

Example 9E: A standard bullion coin was subjected to the gilding process disclosed herein. The coin before and after gilding is presented in Figure 31 A and Figure 3 IB respectively. It is seen that two goals were achieved: first, the surface of the gold coins became substantially gilded; and second, the stamping on the coins was maintained without any visible damages or alterations.

Example 9F: A gold leaf having a grooved surface with groves of about 0.5 mm was subjected to the gilding process disclosed herein. Generally, it is a challenge to successfully gild objects having grooves using electrochemical plating, as it tends to result in non-uniform plating. The leaf before and after gilding is presented in Figure 32A and Figure 32B respectively. It is seen that the goal of successful uniform gilding was achieved.

Example 9G: A gold ring having a non-uniform surface was subjected to the gilding process disclosed herein. The ring before and after gilding is presented in Figure 33A and Figure 33B respectively. Generally, non-uniform surface may result in a non-uniform gilding. However, it is seen that the goal of successful uniform gilding was achieved using the process of the current disclosure.

Example 9H: A gold necklace pendant was subjected to the gilding process disclosed herein. The pendant before and after gilding is presented in Figure 34A and Figure 34B respectively. It is seen that the goal of successful uniform gilding was achieved using the process of the current disclosure.

Example 10: Abrasion resistance test according to BS EN12472

An abrasion resistance test was conducted according to the BS EN12472 standard. The test according the EN 12472 standard is a metric test, where success is achieved when ΔΕ (color distance upon abrasion, i.e. of the tested item before abrasion versus the item after abrasion) is lower than 5.

In the test, two 9K alloys (9K-SCA5 and 9K - OG130A) were gilded according the process of Example 1 ; two similar 9k gold alloys were electroplated with 24K gold; and two similar 9k gold alloys were not gilded. The color parameters of all six alloys were measured and recorded and the alloys underwent the abrasion, following a second color measurement. The color recordings are given in Table 7. In the abrasion step, the tested alloy was abraded using walnuts and abrasion paste as detailed in BS EN12472. "9K-SCA5" refers to a standard 9 karat alloy with an SCA5 master alloy that is composed of 18 wt Ag, 64 wt Cu, 18 wt Zn. "9K-OG130A" refers to a standard 9 karat alloy with an OG130A master alloy that is composed of 12%wt Ag, 71%wt Cu, 17%wt Zn.

Table 7: color changes in gilded alloys upon abrasion

color difference between the same test alloy, prior and after the abrasion test As it can be seen, both the alloys, which underwent the depletion gilding process of Example 1 have ΔΕ significantly lower than 5. As a result, the process passed the BS EN12472 abrasion resistance test. It is further noted that samples #1 and #4, which were gilded according to Example 1, showed the lowest ΔΕ values among the examined samples.

Example 11: Synthetic perspiration test according to ISO 3160-2

A synthetic perspiration test was conducted according to ISO 3160-2 (section 8.4) standard. The test according the ISO 3160-2 (section 8.4) standard is, a qualitative test, where success is defined if no dramatic stains appear on the surface of the tested items as a result of synthetic perspiration. During the test, samples are hanged above a solution containing materials as specified in the standard for a certain period of time in a specific temperature, according to the standard specifications.

In the test, two 9K alloys ("9K-SCA5" and "9K - OG130A", which are as defined above) were gilded according the process of Example 1 ; two similar 9K gold alloys were electroplated with 24K gold; and two similar 9K gold alloys were not gilded. The color parameters of all six alloys were measured and recorded and photographs of the alloys were taken. Thereafter, the alloys underwent the synthetic perspiration test, following a second color measurement and photographing. The color recordings are given in Table 8, and the photographs are presented in Figs 35A-35F and Figs 36A-36F.

Table 8: color changes in gilded alloys upon perspiration

color difference prior and after the procedure.

Figure 35A is a photograph of the 9K-SCA5 alloy after going through the gilding process of Example 1 , but before undergoing the synthetic perspiration test. Figure 35B is a photograph of the same 9K-SCA5 alloy after undergoing the synthetic perspiration test. It can be seen that no stains appear on the surface of this alloy after the test. In contrast, both the electroplated alloy (Figure 35C - before test; and Figure 35D thereafter) and the non-gilded fresh alloy (Figure 35E - before test; and Figure 35F thereafter) got stained after the synthetic perspiration test, which proved the superiority of the current technology in this aspect.

Similarly, Figure 36A is a photograph of the 9K-OG130A alloy after going through the gilding process of Example 1, but before undergoing the synthetic perspiration test. Figure 36B is a photograph of the same 9K-OG130A alloy after undergoing the synthetic perspiration test. It can be seen that no stains appear on the surface of this alloy after the test. In contrast, both the electroplated alloy (Figure 35C - before test; and Figure 36D thereafter) and the non-gilded fresh alloy (Figure 36E - before test; and Figure 36F thereafter) got stained after the synthetic perspiration test.

Example 12: Hardness test

A standard hardness test was conducted using HMV-G 20DT Micro Vickers Hardness Tester by Shimadzu Corporation. The Vickers test is a metric Vickers hardness test. Success in the test is achieved when Hv > 70 (the hardness of sterling silver).

In the test, two 9K alloys ("9K-SCA5" and "9K - OG130A", which are as defined above) were gilded according the process of Example 1 ; two similar 9k gold alloys were electroplated with 24K gold; and two similar 9k gold alloys were not gilded. The hardness of all six alloy was measured as detailed above. The results are sown in Table 9. Table 9: hardness of gold alloys

Generally, the hardness of gold alloys gilded according to the process of Example 1 is comparable with electroplated and non-gilded alloys, which is sufficient for common jewelry purposes of gold alloys. Example 13: Corrosion test according to ISO 9227:2012 section 5.2

A corrosion test was conducted according to ISO 9227:2012 section 5.2 standard. The test according to ISO 9227:2012 section 5.2 standard is a qualitative test, where success is defined if no dramatic stains appear on the surface of the tested items as a result of the corrosion procedure. During the test, samples are sprayed with neutral salts for 24 hours as specified in the standard specifications.

In the test, two 9K alloys ("9K-SCA5" and "9K - OG130A", which are as defined above) were gilded according the process of Example 1 ; two similar 9K gold alloys were electroplated with 24K gold; and two similar 9K gold alloys were not gilded. The color parameters of all six alloys were measured and recorded and photographs of the alloys were taken. Thereafter, the alloys underwent the corrosion test, following a second color measurement and photographing. The color recordings are given in Table 10, and the photographs are presented in Figures 37A-37F and Figures 38A-38F.

Table 10: color changes in gilded alloys upon corrosion

color difference prior and after the procedure.

Figure 37A is a photograph of the 9K-SCA5 alloy after going through the gilding process of Example 1 , but before undergoing the corrosion test. Figure 37B is a photograph of the same 9K-SCA5 alloy after undergoing the corrosion test. It can be seen that no stains appear on the surface of this alloy after the test.

Similarly, Figure 38A is a photograph of the 9K-OG130A alloy after going through the gilding process of Example 1, but before undergoing the corrosion test. Figure 38B is a photograph of the same 9K-OG130A alloy after undergoing the corrosion test. It can be seen that no stains appear on the surface of this alloy after the test. Example 14: Climate test

A climate test was conducted to ensure that items gilded according to the current technology are adequately preserved upon exposure to hot and humid environments. The climate test is a qualitative test, where success is defined if no dramatic stains appear on the surface of the tested items because of the climate exposure procedure. During the test, samples are exposed to 92% humidity environment at temperature of 55 °C for 120 hours.

In the test, two 9K alloys ("9K-SCA5" and "9K - OG130A", which are as defined above) were gilded according the process of Example 1 ; two similar 9K gold alloys were electroplated with 24K gold; and two similar 9K gold alloys were not gilded. The color parameters of all six alloys were measured and recorded. Thereafter, the alloys underwent the climate test, following a second color measurement and photographing. The color recordings are given in Table 11, and the photographs are presented in Figures 39A-39C and Figures 40A-40C.

Table 11 : color changes in gilded alloys upon subjecting to climate test

color difference prior and after the procedure.

Figure 39A is a photograph of the 9K-SCA5 alloy after going through the gilding process of Example 1 and the climate test. It can be seen that no stains appear on the surface of this alloy after the test. In contrast, the non-gilded fresh alloy got stained after the climate test (Figure 39C), which proved that the current technology provides better protection from the environment, compared to untreated samples..

Similarly, Figure 40A is a photograph of the 9K- OG130A alloy after going through the gilding process of Example 1 and the climate test. It can be seen that no stains appear on the surface of this alloy after the test. In contrast, the non-gilded fresh alloy got stained after the climate test (Figure 39C), which again proved that the current technology provides better protection from the environment, compared to untreated samples.

In both samples treated according to the process of Example 1 and undergoing the climate test (Figures 39A and 40A) the color difference prior and after the procedure remained low (around ~1) which indicates that the color remained substantially unchanged.

The foregoing description of the specific embodiments, will so fully reveal the general nature of the invention that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation and without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. The means, materials, and steps for carrying out various disclosed functions may take a variety of alternative forms without departing from the invention.

Claims

A process for dealloying a gold alloy, the process comprising:

heating a gold alloy having an outer surface to a first temperature of at least 150°C for a first time period;

wherein the process further comprises immersing said gold alloy in a fluidized solid composition comprising at least one salt.

The process of claim 1 , wherein the step of heating said gold alloy for the first time period precedes said immersing said gold alloy in a fluidized solid composition.

The process of claim 2, further comprising heating said gold alloy to a second temperature of at least 150°C, for a second time period, following said immersing.

The process of any one of claim 1 to 3, further comprising washing the gold alloy following said immersing.

The process of any one of claim 1 to 3, wherein the gold alloy comprises between 20% to 97% gold and at least one base metal.

The process of any one of claim 1 to 3, wherein the at least one base metal comprises any one or more of silver, zinc and copper.

The process of claim 1 to 3, wherein the fluidized solid composition comprises a plurality of salts.

The process of claim 1 to 3, wherein the fluidized solid composition comprises two salts.

The process of any one of claims 7 and 8, wherein the fluidized solid composition comprises at least one salt having a pKa below 11.

The process of any one of claims 7 and 8, wherein the fluidized solid composition comprises at least one salt comprising nitrate (N(¾^~), chloride (CI ) or sulfate (S0₄ ^~2) ions.

The process of claim 1 , further comprising providing a solid composition comprising the at least one salt and fiuidizing said solid composition in a fluidized bed reactor, thereby obtaining the fluidized solid composition.

The process of claim 1, wherein the steps of heating and immersing occur simultaneously.

13. The process of claim 1, wherein the step of heating occurs prior to, and/or during said immersing.

14. The process of claim 5, wherein said outer surface comprises, prior to said immersing, a first amount of the at least one base metal, and wherein following said immersing said outer surface comprises less than 80% of said first amount.

15. The process of any one of claims 1 to 3, wherein said heating is carried out for a period of time within the range of 1 second to 120 minutes.

16. The process of claim 1 , wherein said gold alloy is selected from the group consisting of jewelry, coins and decorations, wherein the item of jewelry is selected from the group consisting of rings, necklaces, watches, earrings, nose rings, body piercing rings, collars, chains, charms and bracelets.

17. A dealloying apparatus, comprising:

a heating unit comprising a heating unit internal shaft having at least one heating unit opening, said heating unit is configured to generate a temperature of at least 150°C;

a fluidized bed reactor comprising a freeboard and a fluidized bed internal shaft having at least a proximal opening; and

a leverage unit comprising an elongated transport member, said leverage unit is configured to drive the elongated transport member through the at least one heating unit opening into the heating unit internal shaft, and from the at least one heating unit opening, through the at least one fluidized bed proximal opening into the fluidized bed internal shaft.

18. The apparatus of claim 17, wherein the at least one heating unit opening comprises a heating unit proximal opening and a heating unit distal opening, and wherein the leverage unit is configured to drive the elongated transport member through the heating unit proximal opening along the heating unit internal shaft, and from the heating unit distal opening, through the fluidized bed proximal opening and into the fluidized bed internal shaft.

19. The apparatus of claim 17, wherein said elongated transport member is formed as a rod.

20. The apparatus of claim 17, wherein said elongated transport member further comprises a placement section configured to accommodate an article holder.

21. The apparatus of claim 17, wherein the fluidized bed reactor further comprises a gas distribution unit configured to distribute gas flowing therethrough.

22. The apparatus of claim 21, wherein the fluidized bed reactor further comprises a mesh sieve and a distributor, wherein the distributor is flexible, soft and comprises a plurality of apertures.

23. The apparatus of claim 21, wherein the gas distribution unit comprises an inlet tube fitting, and at least one nozzle body connected to a nozzle head, wherein the nozzle head comprises at least one outlet orifice, and wherein the inlet tube fitting is configured to allow gas flow into the gas distributor unit, through the at least one nozzle body, towards the at least one orifice of the nozzle head thereof.

24. The apparatus of claim 21 , wherein the gas distribution unit comprises at least one outer distribution tube and at least one inner distribution tube having at least one outlet orifice.

25. The apparatus of claim 17, further comprising at least one motion unit heat sensor attached to the elongated transport member.

26. The apparatus of claim 18, wherein the heating unit further comprises at least one heating unit heat sensor.

27. The apparatus of claim 18, wherein the fluidized bed reactor further comprises at least one fluidized bed heat sensor.

28. The apparatus of claim 17, wherein said fluidized bed reactor further comprises a fluidized composition level sensor.

29. The apparatus of claim 17, wherein said apparatus further comprises a camera.

30. The apparatus of claim 17, wherein said fluidized bed reactor further comprises a fluidized composition consumption sensor.

31. The apparatus of claim 17, wherein said heating unit further comprises a first plate closure and a second plate closure adjacent to the at least one heating unit opening and configured to be displaced between a close state and an open state.

32. The apparatus of claim 17, wherein said apparatus further comprises a washing unit.

33. The apparatus of claim 17, wherein said apparatus further comprises a microcontroller configured to control at least one operation of any one or more of the leverage unit, the heating unit and the fiuidized bed reactor.

34. The apparatus of any one of claims 26 and 30, wherein the microcontroller is further configured to control at least one operation of the camera.

35. The apparatus of any one of claims 29 and 30, wherein the microcontroller is further configured to control at least one operation of the washing unit.