US3035997A - Appliances for cleaning silver and silver-plated articles - Google Patents

Description

y 2, 1962 M. T. H. GROSS 3,035,997

APPLIANCES FOR CLEANING SILVER AND SILVER-PLATED ARTICLES Filed June 25, 1956 United States The present invention concerns durable appliances for removing the tarnish (which consists mainly of a sulphur containing silver compound) from articles and objects made from silver and from silver-plated articles and objects. In particular it concerns durable appliances useful for household purposes. The effectiveness of my appliances is due to the formation of an electrochemical couple of the tarnished silver surface and the metal from which my appliance is made when they are brought into contact in a liquid medium.

It is known that silver may be cleaned electrochemically by forming a couple with a less noble metal. The known processes are however not simple and reliable enough to be well suited for household purposes. I have for instance found that when the silver articles to be cleaned are immersed in water in a magnesium bowl the magnesium soon corrodes, especially at the places of contact with the silver, forming a dark layer which breaks the circuit. In such places spots which are difiicult to remove may even appear on the silver. When aluminium in various shapes is used such layers are also formed, breaking the contact between aluminum and silver, and alkaline solutions have to be used as liquid medium in order to obtain any action at all. This makes it necessary to rinse the silver objects thoroughly after cleaning and, in addition, the coating formed on the aluminium has to be removed after each cleaning procedure. Furthermore plates of Zinc have been used in acid or alkaline solutions. This method also has the disadvantage that the cleaning process has to be carefully controlled and that the silver objects have to be thoroughly rinsed after cleaning in order to remove all remnant of acids or alkalis which would otherwise be harmful to the silver or would at least accelerate the forming of a new layer of tarnish. Although this method may give good results in museums or factories where it can be carried out under expert supervision, it is not suitable for domestic purposes as most housewives would prefer not to entrust their silver to possibly harmful liquids and would wish to avoid the task of preparing solutions of acids and alkalis of defined concentrations.

I have now found that it is possible to produce silvercleaning appliances based on the formation of an electrochemical couple zinc-tarnished silver surface which are effective in water, for instance tap water. These appliances last a very long timealmost indefinitelysince they are only consumed in the actual removal of the tarnish, the liquid medium being free of acids and alkalis which attack zinc.

It is surprising that such a couple should work in water since zinc is more noble, and may therefore be expected to be less effective, than aluminium which only works in alkaline solutions. I have found that in order to obtain an eificient cleaning action with a structure made of Zinc in water it is necessary that the current can pass from a relatively large zinc surface through relatively short distances to the silver surfaces to be cleaned. I have also found that zinc wire is a material very well suited for this purpose since by closely arranging a length of it a structure having a large zinc surface area is obtained which, owing to the flexibility, pliability and softness of the wire can easily be arranged, in the water, in such a manner that it provides short paths for the current to atenr "ire the silver surfaces to be cleaned and which, after the cleaning, can be brought back easily by hand to its original well defined shape.

The essential features of my invention are illustrated in FIGURES 1 and 2 of the attached drawing.

The appliance shown in FIGURE 1 consists of a zinc wire helix on a red, the helix being made say of 50 feet of zinc wire of a diameter of 2 mm. and the rod being for example 2 feet long and 1 inch thick. Owing to the pliability of zinc wire the helix when removed from the rod can be drawn out and shaped for the cleaning procedure in a bucket or sink or the like in such a manner that when it is in touch with the silver objects under Water the current paths from the whole Zinc surface to the silver surfaces are short. After the cleaning is complete the helix can easily be reshaped on the rod on which it is stored.

FIGURE 2 illustrates the manner in which such a drawn out helix can be arranged by being hooked over the rim of a bucket and drawn along its walls and bottom. More than one helix can, of course, be used if desired. After the bucket has been filled with water and the silver articles immersed so that they either directly or indirectly are in contact with the helix the cleaning proceeds evenly.

The drawing therefore shows by way of example a durable appliance (which is the subject of the present invention) for the cleaning of silver and silver-plated articles by immersing them in a liquid medium and therein bringing them into contact with a less noble metal comprising a structure made essentially of zinc and formed in such a manner that, in the said liquid medium, it fulfills the requirements of firstly offering a zinc surface of high specific activity and secondly permitting to arrange, with various amounts and sizes of the articles to be cleaned, the relative position of zinc surfaces and silver surfaces to each other so that Zinc surface of high specific activity is in the vicinity of the silver surfaces to be cleaned, thus allowing the cleaning reaction to take place in Water as the liquid medium and the consumption of zinc to be practically limited to the said cleaning reaction, wherein the relevant parts of the said zinc structure consist of at least one closely arranged length of zinc wire capable of being, by hand, easily adapted to fulfil the said cleaning requirements and of being easily reshaped after use.

Preferably a support is provided for reshaping the zinc wire and retaining it in its shape.

The area of contact between silver and zinc surfaces can be small as the current passes easily from the one metal to the other and no layers breaking the contact are formed. If desired the zinc may be in contact with one silver object only and this one in direct or indirect contact With the others.

By the expression a structure made essentially of zinc is to be understood a structure of which the relevant parts consist of zinc, the Zinc being of substantial thickness so as to make the appliance a durable one.

The expression: the structure being formed to have a surface of high specific activity means a structure whose surface when brought into contact with a silver object in water is capable of producing a current that is considerably greater than the current produced by a, say circular, smooth flat zinc plate of the same surface area in contact with the same silver object.

The following example will explain this: If a smooth flat zinc plate resting on the bottom of a container filled with water is brought into contact with a silver object, the zinc surface facing downwards will not contribute substantially to the flow of the current towards the silver object, because firstly the water has not free access to it and secondly even if its contact with the water were adequate the paths of the cur-rent passing from it round the zinc plate to the silver object would be very long in comparison with the paths from the upper surface. In a struc-, ture consisting of a closely arranged length of zinc wire, on the other hand, the current can pass from every point of its surface to the silver surface'of the object in contact with it on short paths whereby the cleaning efiiciency of the zinc surface is much increased.

According to a preferred mode of execution of my invention such a structure which is specially well suited for household purposes consists of a helix of zinc wire which can be drawn out to the desired length and shaped to surround the silver articles and reshaped on a rod after use.

' I used, for instance, with very good results zinc wire made from a cast billet of Seacliff brand zinc by extrusion, rolling and finally drawing, which wire was of a purity of 99.95%. Zinc wire of lesser purity (99.5%) and zinc wire of higher purity (99.99%) proved also very satisfactory. Zinc wire of various diameters can be used, but I found wire of more than 3 /2 mm. diameter too heavy and stiff and wire thinner than 1 mm. diameter not substantial enough in continued use. The thickness I prefer is between 3 mm. (541) and 1 /2 mm., both limits included. Wire of 2 mm. diameter was very frequently used.

Each of the two ends of a length of about fifty feet of the wire were smoothed in order to protect the silver from being scratched and then the wire was shaped to a helix of about 1 diameter. The length of the helix was about 1 /2 feet when closely wound. Into the helix was inserted a wooden rod of a diameter slightly smaller than the inner diameter of the helix and long enough to protrude at both ends (cg. about two feet long). When notin use the helix is kept on the rod. To keep it from sliding off rubber rings may be pulled over the rod on both ends or wedges may be inserted into the first few tumings of the helix, or the: like; the thinner kind of wire however will keep on the rod by itself. In making different appliances I chose different diameters of the helix according to the thickness and softness of the wire and the length to which I wanted to draw it out during cleaning. I found however a diameter of about 1" to be suitable for all wires of the diameters of lmm. to 3 mm. If in the cleaning process zinc surface of a specially high activity is wanted then, according to a further feature of the invention, the structure may consist of zinc wire helices which are of di'lferent diameter so that they can be pushed into one another. In this case the outer diameter of the inner hel x has to be slightly smaller than the inner diameter of the outer helix.

The lengths of the zinc wire used in making different appliances may diiferin accordance with the amount of silver for the cleaning of which they are usually to be employed. Thus, for the cleaning of household cutlery, for instance forks whose prongs are stained by eggs and the like, a very short helix, say one made of wire of foot length, will be most convenient. Such a small helix may be coiled on the bottom of a jug filled with water and the forks, instead of the usual rinsing after the washing up, inserted between its turns. In general I have found it preferable to use several shorter helices, say three made each from a length of Wire of fifty feet, rather than one three times as long since it is easier to reshape them and also to store and transport them.

:For the cleaning process the helix was removed from the rod, drawn out, if desired, and placed in a bucket made preferably of non-conducting, for instance plastic, material (although stainless steel is also very suitable} in such a manner that every silver surface to be cleaned had some of the Zinc wire near to it. When I wanted to clean so many silver articles that they filled the bucket I hooked one end of the helix over the rim of the bucket and drew the helix to huch a length that I could lead it down along the inside of the wall of the bucket, across the bottom and up the opposite wall Where again I hooked it over the rim. Using a helix of 1 diameter (made of 50 feet of wire of 2 mm. thickness) '1 found it easy to draw it out to about 3 or 4 times its closed length and to reshape it on its rod after cleaning. No difiiculty was encountered in reshaping the helix even when it had been drawn out to six times its closed length. On the other hand, when I had a few small articles only it sufiiced to draw out the helix to such a length, it at all, that, coiled together, it covered most of the bottom of the bucket. In this case I simply laid the silver articles on the coiled helix or inserted them between the coils. In this Way the cleaning of the silver articles proceeded very evenly after the bucket had been filled with water.

The water used was that provided for household use by the municipal authorities in Eton, Buckinghamshire. One sample which was analysed had a hardness of about 360 and contained approximately 56 parts per million chlorine as chloride. Should the conductivity of the water'to be used be too small, as for instance may be the case with rain water or distilled Water, it can easily be adjusted by the addition of very small amounts of electrolytes harmless to the silver surfaces. Such an ad dition can, if desired, also be used to increase the conductivity of tap Water. Very dirty articles should preferably first be freed from grease etc. by washing them with a solution of a detergent or the like. If desired a small amount of a detergent and/ or a Water softener may be added to the bath. df the coat of tarnish is very thick the tarnish does not disappear completely while the article is in the water but is loosened and can easily be wiped away from the surface. The cleaned articles should be very Well dried. I have found that their brilliancy and their resistance to tarnish formation is increased if they are allowed to stand in air some time and then are wiped again. When the cleaning was complete the helix was dried and then put back on the rod and reshaped.

When the helix loses its shine this can, if desired, be restored by rubbing the helix while on the rod with a cloth or brush, for instance a nylon brush, so that the turns make little movements on the rod and towards each other. In this Way the cloth or brush effects the cleaning of the outer surface of the helix, the rod rubs and cleans the inside and the surfaces of the turnings facing each other are cleaned by their rubbing each other. Sandpaper may also be used to restore the pleasing appearance of the appliance.

Since the appliances according to the present invention are used in Water as liquid medium which does not harm the silver and since furthermore the zinc practically ceases to dissolve when the cleaning is completed, it is very easy to control the cleaning process. The cleaning appliance and the silver articles may, if desired, be left in the water for a long time, for instance over night. It must however be emphasized that such long immersions-while never being harmful-are necessary only in cases where the silver is extremely badly tarnished, whereas ordinarily tarnished articles will be cleaned in a matter of minutes or even seconds. Furthermore the cleaning process is very gentle. After cleaning the silver objects need not be rinsed since the cleaning liquid remains practically pure water, and therefore no danger exists that remnants of acids, alkalis or other chemicals remain on the cleaned articles and accelerate tarnishing. After cleaning the silver articles are uniformly bright and exceptionally resisting to formation of tarnish.

The described zinc helix on a rod has many advantages in addition to those already mentioned: It is very easily adaptable for the cleaning of silver objects in varying amounts and of various sizes. It can be used in any kind of vessel. The concentration of zinc surface area near the silver surfaces can easily be regulated, for instance it is possible to put a large part of the helix near those silver surfaces that are more tarnished than others or to insert into the helix at such places a helix of smaller diameter. When the appliance -is not in use it needs very little space which is of importance for its use in the household, for transporting, storing and selling it. Its production is simple and cheap. It is easy to clean. There is no danger of scratching the silver in the cleaning. The Wear of the zinc which is greater on bends and edges than on other points is, with a helix, absolutely even, whereby the duration of life of the appliance is still further prolonged and a still more uniform working is made possible.

Apart from cleaning silver and plate the appliance according to the present invention has proved very successful in cleaning and greatly improving the appearance of articles in Damascened work where the great difference in hardness and chemical activity of gold, silver and iron makes other processes dangerous to the objects. It should however not be used in the cleaning of silver articles that have intentionally been partly blackened by forming sulphur compounds of the silver.

What I claim is:

A process for the cleaning of silver and silver plated articles by immersing them in a liquid medium and therein bringing them into contact with a durable appliance consisting of a detached zinc wire helix, the diameters of the wire and of the helix being so selected in relation to each other making possible adjusting the helix, adjusting it to size to fit the cleaning of various amounts and sizes of the said articles, said helix maintaining its shape when not interfered with, easily and by hand drawing out to a helix of the desired length and shaping it to surround a heap formed by the said articles and, easily and by hand, reshaping to its original length and shape after use.

References Cited in the file of this patent UNITED STATES PATENTS Re. 13,880 Keyt Feb. 16, 1915 577,134 Harrison Feb. 16, 1897 1,074,782 Ennis Oct. 7, 1913 1,093,236 Applcby Apr. 14, 1914 1,139,686 Kcyt May 16, 1915 1,941,040 Mann Dec. 26, 1933 2,451,064 Butler Oct. 12, 1948 2,765,273 Lobos Oct. 2, 1956

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