CA1037788A - Electrostatic method of coating glass articles with a powder of glass enamel to simulate a sandblasted or etched appearance - Google Patents

Electrostatic method of coating glass articles with a powder of glass enamel to simulate a sandblasted or etched appearance

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Publication number
CA1037788A
CA1037788A CA199,619A CA199619A CA1037788A CA 1037788 A CA1037788 A CA 1037788A CA 199619 A CA199619 A CA 199619A CA 1037788 A CA1037788 A CA 1037788A
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CA
Canada
Prior art keywords
glass
enamel
article
particles
frit
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA199,619A
Other languages
French (fr)
Inventor
Earl A. Riffle
Herbert C. Shank (Jr.)
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Anchor Hocking LLC
Original Assignee
Anchor Hocking LLC
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Filing date
Publication date
Priority to US36018173A priority Critical
Application filed by Anchor Hocking LLC filed Critical Anchor Hocking LLC
Application granted granted Critical
Publication of CA1037788A publication Critical patent/CA1037788A/en
Application status is Expired legal-status Critical

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Classifications

    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03CCHEMICAL COMPOSITION OF GLASSES, GLAZES, OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C17/00Surface treatment of glass, not in the form of fibres or filaments, by coating
    • C03C17/02Surface treatment of glass, not in the form of fibres or filaments, by coating with glass
    • C03C17/04Surface treatment of glass, not in the form of fibres or filaments, by coating with glass by fritting glass powder
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03CCHEMICAL COMPOSITION OF GLASSES, GLAZES, OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C17/00Surface treatment of glass, not in the form of fibres or filaments, by coating
    • C03C17/02Surface treatment of glass, not in the form of fibres or filaments, by coating with glass
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03CCHEMICAL COMPOSITION OF GLASSES, GLAZES, OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C8/00Enamels; Glazes; Fusion seal compositions being frit compositions having non-frit additions
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03CCHEMICAL COMPOSITION OF GLASSES, GLAZES, OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C8/00Enamels; Glazes; Fusion seal compositions being frit compositions having non-frit additions
    • C03C8/02Frit compositions, i.e. in a powdered or comminuted form
    • C03C8/10Frit compositions, i.e. in a powdered or comminuted form containing lead
    • C03C8/12Frit compositions, i.e. in a powdered or comminuted form containing lead containing titanium or zirconium
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03CCHEMICAL COMPOSITION OF GLASSES, GLAZES, OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C2205/00Compositions applicable for the manufacture of vitreous enamels or glazes

Abstract

METHOD OF SIMULATING A SANDBLASTED OR ETCHED
APPEARANCE ON GLASS ARTICLES

Abstract of the Disclosure A method of simulating the appearance of a sand-blasted or chemically etched surface on a glass article. A
glass enamel which includes both a glass frit component and an inorganic pigment component is prepared in dry powder form, and is applied to the heated article by the electrostatic dry powder spray process. After coating the article is fired to fuse the frit, but the firing is carried out incompletely and at a temperature insufficient for the frit to flow out as smooth continuous film, so that the enamel presents a matte appearance.

Description

.

~03 ~ ~8 This invention relates to a method of applying a matte finish to glass articles. The metllod is especially useful for simulating the appearance of glass that has been sandblasted or chemically etched, because it eliminates several disadvantages of those techniques.
Sandblasting is widely used in the glass industry to impart a rough, "frosted", or matte surface on glass ; articles. It is used in some cases puroly for purposes of decoration or identification, because it provides a distinctive surface treatment. Such use is exemplified by the distinctive . . ~ tra~erna f~
B appearance of the glass containers in whicll "Gilbey'~brand gin is sold. In other instances, a sandblasted surface is used for its functional characteristics, as in electric light globes and fixtures, to diffuse or soften the light from the filament.
The sandblasting technique involves directing a shower of high - velocity abrasive grit particles against the glass surface, which remove chips or fragments so small as almost to be in-visible to the unaided eye. By tlle removal of such microscopic chips, a roughened surface is obtained which creates the desired matte appearance.
The sandblasting tecllnique inherently presents certain disadvantages, some of which are mechanical and others of which are aesthetic in nature. ~linute particles of grit and/or abraded glass remain loosely adherent on t}-e roughened surface.

-2-10377~
These are gradually dislodged from the article as it is subsequently handled or used. Such exfoliation of chips or fragments can create an abrasive environment which greatly increases the rate of wear of equipment used for inspecting, labeling, filling and/or cartoning the sandblasted articles.
For example, grit remaining on beverage containers which have been sandblasted greatly accelerates the wear of certain filling line equipment, loading to much shorter machinery lifetimes than would be obtained if the containers had not been sandblasted.
Because the sandblasting process is essentially one of erosion, it removes the smooth "as manufactured" skin of the glass article, and it reduces the thickness of the glass wall. As a result, the mechanical strength of the article is somewhat reduced. Because of this and the wear caused by adherent grit particles, filling lines are often run at a slower rate when handling sandblasted containers than would otherwise be necessary. Moreover, in use the article will display less durability in response to scratching, impact, and so on.
` Apart from the foregoing "mechanical"
problems caused by sandblastirg, the technique causes certain aesthetic difficulties as well. The loosely adherent particles have

- 3 -,, . . : ... ..
. .

~.Q37~78~3 an affect on the appearance of the surface, and if they are even partially removed as by splash or by wiping, the ap-pearance of the article is quite noticeably changed so that it appears to be streaky, spotted or generally non-uniform.
If a glass bottle which has been sandblasted is l~ashed but is not dried very carefully, it will thereafter look different, and it may look as if it actually were dirty. l`his factor is particularly adverse, from a commercial standpoint, where the article may be exposed to water splash in use (as a beverage container is). Water drops form conspicuous strea~s or spots. The adherent grit could of course be removed in manufacture by a thorough scrubbing, but that is expensive and slow. The grit also tends to wipe off onto cloth, and shows up as a W]litis]l po~dery smear whicll is especially visible on dar~ cloth. While these difficulties are primarily aesthetic rather than mechanical, they are nonetheless of considerable importance to the manufacturer whose product is sold in such containers and wllose customers' preferences may be affected by such factors.
In the glass container industry it is a common practice to ap~ly what is called a "lubricity" coating to glass articles that are to be handled on lligh speed lines.
~s is well known, sucl; coatings reduce the susceptibility of the glass surface to the scratching or abrasion that is .

~ ~037q~8 ~

incidental to manufacture, sllipping, or use. Oleic acid is ¦l often used as a lubricity coating, and is applied as a va~or or sprayed on as a water emulsion for that purpose. If a lubricity coating such as oleic acid is applied to a sandblasted article, the presence of the coating on the glass markedly changes the reflective quality o the surface with the result that the lubricity coated article has an oily appearance. This has limited use of lubricity coatings on sandblasted articles.
Another adverse affect of sandblasting has to do ~ith "labelability", that is, the ability of the surface to receive an adhesive label. The loosely adherent grit particles prevent good adhesion of the label to the underlying glass;
in effect, the label sticks in local areas to grit, rather than to the article. The result is that the label is more readily dislodged or removed. ~loreover, if an improperly applied label (e.g., a misaligned label) is intentionally removed by water soa~ing, tlle water, as already noted, alters the surface, and leaves the container with a changed appearance.
}lence sandblasted bottles tllat have been mislabeled generally cannot be acceptably relabeled. This is a distinctly adverse factor in the beverage industry, since beverage containers are filled before the labels are applied.
By reason of the foregoing, it has been desirable to provide a technique for imparting an 'limitation" sandblasted surface treatment for glass articles. A technique has been 1~;1778~

needed W]liCh will very closely approximate the appearance of a sand~lasted surface, but which will not carry with it the attendant disadvantages of sandblasting. ~xactness of similarity in apl)earance to a sandblasted surface is especially important in the instance of beverage containers, so that bottles with the new surface treat~ent can be sold side-by-side with containers having a sandblasted surface, during a period of manufacturing change-over from one to the other without difference in appearance whic}l migllt imply that the containers are of different quality or contain a product that is different.
It is recognized, of course, that it is possible to impart a roughened appearance to a glass surface, sometlling like a sandblasted appearance, by use of chemical etchants. The surface of a glass article that is sprayed with or immersed in a water solution of hydrofluoric acid is etched and will display a frosted or semi-matte appearance, somet]ling li~e that of~a fine or light sandblast treatment. The visual cor-respondence is not very exact, however, because the acid etclled surface is much finer grained, i.e., less roug]l, and also because etching neither produces nor leaves any C]lipS
on the glass surface. ~loreover, some of the same difficulties attendant the sandblasting surface treatment also accompally etching, and disposal of the waste materials from the etching process is difficult.

' The most serious objection to acid etching is its cost; it re~uires use of expensive etchant, reduces line speed by the considerable time required for contact with the etchant bath, and it requires a final wash.
Against this backyround, this invention is directed to a glass surface treating method which provides the needed substitute for sandblasting and which at the same time avoids virtually all the objections to the latter. It enables a surface condition to be produced which --to the unaided eye-- very closely matches the sandblasted surface.
(There are, however, surface differences not visible macro-scopically but apparent microscopically which impart surprising and unexpected advantages to the product). The new method can be modified to produce a surface of finer "grain", less rough, which closely approximates an etched surface. It thus is useful as a replacement for either sandblasting or chemical etching.
In contradistinction to both sandblasting and chemical etching techniques, the new method involves the addition of material to the glass surface, rather than the `~
removal of material from it. The surface addition is carried out through a particular technique of applying to the surface a glass-containing dry powder of certain characteristics, but only partially fusing the glassy powder so that some of the discreteness of the applied particles is retained.

' ' '' , ' ' `.' ' '': ' ,' ~ roadl ~ ~ 7e~ssed, the method of this invention involves the preparation of a dry powder coating material which is a glass enamel having a low melting glassy `~ frit component and a refractory inorganic pigment component.
The article is preheated to make it electrically conductive, preferably to about 150 to 250F. The enamel is then applied by an electrostatic dry powder spray process. The temperature of the article is insufficient to fuse frit to it, but the powder adheres electrostatically. After coating, the article is fired, but only incompletely. A low firing temperature is used which adheres the frit to the glass; however, although - the firing is carried out above the softening temperature of the frit, the frit is not allowed to flow out into a smooth continuous film. As the result of such incomplete firing, the enamel presents a matte finish. ~ -More specifically, the coating material used in the new method is a fusible particulate mixture consisting ; essentially of a glass frit and a minor amount of a refractory ; 20 inorganic pigment. This material is referred to hereinafter as a "glass enamel". When the frit component is heated so that it bonds to the glass surface, it in turn bonds the pigment particles, which are not fu_ed.

~ ~'' ' '' . .

'~ -~ 8 -103778~
Typically the glassy or frit component includes lead oxide as the major component. 1{igll lead borosilicate frits whic11 are lot. melting are especially useful, and include silica and boric oxide as the other primary components. The frit may and preferably does include soda, alumina, TiO2, and Zr2 or ZrSiO4 as other components. Glass frits of this composition are well kno~n in the art, and are sold by numerous manufacturers. Frits of the ollowing composition : are commercially available, and,are especially suitable:
' wt. % ,, S-iOz 25 to 30%

2O3 5 to 10%
Na2O 3 to 7%
PbO 45 to 55%
ZrSiO4 5 to ,10%
TiO2 2 to 5%
, Al2O3 . 2 to 5%
' In the production of the glass enamel, a glass-making batch, for example of the foregoing composition, is ' compounded and melte~ to form a glass. The molten glass is then quenched in water to form a frit. The frit is reduced to finer particles, as by ball or pebble milling. To the frit is blended an inorganic pigment (usually TiO2, if a "whito" col~ is desired). The piament is usually milled ~ 9 :- .: : : . - .. .. - . -10377t~8 with tl-e frit as an additive, and is not actually a melt component with tlle frit. lt should be noted that the frit may itself contain ~iO2 as a melt component, however that does not act as the pigment.
It is believed important, to obtain the improve-ment in properties described above, that the ratio of frit to refractory pigment be relatively high. ~ood results are obtained wllere the enamel has a frit content of about 99~
and a pigment content of about 1o l~t. ~lore broadly, the %
frit in the enamel may be in the range of about 80-99.5~.
In general, other things being equal, increasing the percent of frit tends to produce a smooth glossier surface, while increasing tho proportion of refractory pigment tends to produce a more matte surface and, if carried too far, can lead totard the same defects as displayed by sandblasting itself.
For use in this invention it is desirable that the frit components of the gl?ss enamel have a softening point .ell belo~ that of the glass article itself, and that it have a coefficient of expansion substantially matching or just below tllat of the glass. Most preferably the frit expansion should be about 5 to 10 x 10-7 in/in/C. less than the base glass in order for it to be in slight compression or neutral in strain on the coated article.
In tlle past, glass enamels have been used for ~et spray application to glass, and for sil~ scrcen application in t~hat is known as the "ACL" process, meaning applied color labelin~. For that purpose they are commonly supplied in the form of a wet slip, containing either water or an organic vehicle. In ACL use, when the enamel has been applied to a glass surface, it is fired to drive off the liquid carrier and to fuse it to form a smooth glossy continuous film that will have an appearance like an enamel paint.
In the practice of this inve]ltion, however, the frit must be used dry, Wit}lOUt a suspending fluid. This is aehieved either by dry milling the glass frit and pigment to form the fine particle material, or by wet milling followed by a drying operation to remove the water or other added fluid.
No additives are required, altllough it may be desirable to incorporate other components for special purposes.
In accordanee with the new met}lod tlle coating material is sprayed onto the article by the use of eleetro-static dry powder spray apparatus. The powder is sprayed, without any liquid component, in the form of a "smo~e" or mist, carried from a powder spraying ''gWI'' by a mild air current. The powdçr is charged electrostatically as it issues from the gun, and the article to be coated is grounded or charged oppositely, so that the charge attracts the powder particles to the article and adheres them to it. The spraying and charging apyaratus may be of known type, and suitable ehar&ing equipment is commercially available as indieated llercinafter .
' . ~ ' . . . . ...
.

It may be desired to apply the matte surface treatment only to selected portions or areas of thc article surface. In that event portions of the article t.~hich are to remain clear are masked. Thc electrostatic charge holds the enamel particles to unmasked glass areas, and to the mask which is removed prior to the subsequent firing operation.
The final iring step is of critical importancc in obtaining the desired matte finish. Conventionally, glass enamels are ired to such extent that the discrete particles completely fuse and coaslece, so that tlley form a continuous, smooth, glossy film. In this invention, however, the particles are "underfired", that is, the duration and/or ~emperature of the firing cycle is restricted so tllat the firing is sufficient to cause the applied coating particles to form a secure bond Wit}
the underlying glass surface, but is insufficient to cause tlle particles to lose all of their discrete individual cllaractcr (as seen under the microscope) or to flow out as a contlnuous smooth film. Por tllis purpose, the peak firing temperature is desirably about ~0 to 300 F. above the softening point of the enamel frit component, but below that of the base ~lass.
It is recogllized tllat, broadly speaking, electro-static powder deposition processes have previously been used to coat glass articles. Refractory particles have been applied by a form of electrostatic dry powder application, to the interior surface of li~ht bulbs, so as to form a frosted . . ~. . . - , 10377~38 finish whic]l cliffuses the light from the filament. I~owcver, the coating material uscd is most commonly silica, as showr for examplc in patents No. 2,811,131; 2,988,458; 2,995,463 and 3,125,457. Other patcnts relating to tlle use of electro-static dry powder spray for coating lamp envelopes show the use of bone ash (No. 2,970,928), and wollastonite and alu~ina (No. 2,878,136) as the coating material. Such materials are essentially infusible at temperatures l>clow the softening point of the glass from which the bulb is made, and the coating particles are not fused or softened but remain as discrete particles which are partially imbeddcd in the softened glass surface. Thcy do not present the rounded contours produced in accordance with this invention.
Apparatus for the clectrostatic dcposition of enamel on an iron bathtub is taught in No. 3,058,443. ~ very smooth surface is of course required, and a rough "sandblasted"
effect would be altoge~}lcr unsatisfactory.
The elcctrostatic application to bottlcs of glass color labels is taught in No. 3,238,053. The patcnt teaches the desirability of preheatillg the glass to a temperature above 752 F. so that the glass will have a sufficient conductivity to accept a cllarge of thc intensity that it will attract oppositely charge(l, relatively cold, glass colors.
The particlcs arc said usually to melt the instant they strike the ~IOt glass and remain fix~d by tllcir own adhcsive. The color is applied through a charged screen, and is fused to "level" it and obtain a glossy pattern.
Dry powdcr enamels for electrostatic deposition on l~eated glass bottles arc taught in Nos. 3,400,000 and 3,437,504.
In the process they disclose, the enamel is applied through an offset platc, whic]l is disadvantageous where a highly curved three-dimensional glass objcct is to ~e coated, or through a charged screen. The powder is fired to form a slick, paintlike surface, which has no relation to a sandblasted surface.
. In No. 3,442,748 silica powder is applied electro-statically to newly formed shect glass, which is then calcndered to adhere thc particles.
No prior art is known whicll shows a method for achieving a matte surface ~y clectrostatic dcposition of dry powder glass color, wllerein the frit is partially or in-completely fused to a degree such that thc particles are adhered but present rounded contours when vicwed under the microscope, and do not coalesce to form a smooth film.
The drawing is a graphical representation of the pre-ferred time-temperature firing cycles for producing a sand~lasted appearance and an acid etched appearance, respectively, on glass articles in accordance with the invention.

The following examples represent specific ~rocesses for carrying out the method of this invention, but they are not to be taken as signifying the only compositions or conditions by wllich the desired results can be ohtained.
; EX/',rl~LE I
This example represents t]le presently preferred tecllnique for imparting a simulated sandblasted appearance to alcollol beverage containers of soda lime glass. Such containers are usually of the following approximate oxide composition:

, Si~2 - 69 to 73.5%
Fe23 ~ .01 to .05%
A12O3 - .5 to 4.0%
CaO - 5.0 to 14.U%
~lgO - 0 to 5.0%
Na2O - 12.0 to 18 K2O - 0 to 4%
~linor Ingredients - 0 to l~o ¦ Tlle specific glass composition used in tllis example had a softening point of 1362 F.
The containers were molded by a conventional press and blow process and were ~enerally square in cross-section, witll rectangular sides and a shoulder portion that tapered conically to tlle finish or closure-receivin~ portion. Three sides, but not tlle fourt]l, of the container were to be finished matte, while the fourtll side was to remain clear.

.. . . ~
- . .: . . ~ . ; , : .

S~Q37~'~8 ; A glass enamel was prepared in dry po~der form from ; a high lea~ ~orosilicate frit in accordance WitJl the oxide composition previously set forth. The softening point of the frit was al)proximately 900~ ~. The frit was mixed with Ti~2 pigment in the ratio of about 99:1. The enamel was prepared in dry powder form by dry milling in a ball mill without addition of water. The frit particles in the enamel ranged in size from sub-micron particles up to about 60 microns; the pigment particles were about l/2 micron in mean size.
The particulate enamel was placed in the hopper of ; an electrostatic dry powder sl~ray apparatus. The particular spraying apparatus used was a commercially available "Gema 720"
system manufactured by Gema A.G. St. Gallen, Swit~erland.
In preparation for coating, the container ~as gripped by a chuck which supported it from the finish or closure receiving portion. The finish and a part of the shoulder surface beneath it were masked. A mask was also applied to the one side wall of the container to W]liCll the matte finish was not to be applied and to the bottom.
The article in the chuck, was preheated to a temperature in tne range of roughly 150-250 ~. Higher temperatures are suitable so long as they do not soften the enamel frit particles to the extent t]lat they would adhere to the ~lass surface, or to the chucking or masking fixtures.

Temperatures as higll as 450 F. have been tested, but such high temperaturcs present no advantagc, require longer prc- ¦
heating, and could present a danger of thermal shock. Specificall~
200 ~. has been found quite suitable. This tem~erature is suf-ficient to establish uniform conductivity of the ~lass surface, as required for the electrostatic dry powder spraying.
The coating apparatus was operated at a material feed pressure of 15 to 20 psi, a dosing pressure of 1~0 psi, and a voltage of 70,000 v. The coating was ap~lied by hand-lleld spray gun, at an average weig}lt of about 0.0004 oz. per square inch.
(Coating weights in the range of abou~ 0.0002 - .0006 oz./in ; are generally useful.~ The powder was not heate~ prior to con-tacting the article, and was essentially at room tempcrature.
l After coating, the powdery coating remained adhered to the glass surface by electrostatic attraction, however, the ~articles were not bonded to thc glass alld could be dis-lodged, as by an air jet. Overspray powder was recovered for rcuse. This permittcd a very llig}l coating use efficiency, and coating utilizations of up to 90% or bctter on a weight basis can be achieved. Reprocessing of the coatin~ is not required for reuse.
The mas~ was removed from that side of the article whic}l was to remain clear. Coating W]liC}I adhered electro-statically to the mask was easily removed by an air jet, so that no fused l)uildup accumulated Oll the mas~. A sharp mask line was present on the container.
. . ~

~ : - -. , The article was then carrie~ into a lehr in W]li it t~as fired. Tlle firing cycle used is shown in the dra~ing as the curve labeled A. Ihe peak temperature (about 1080 F.) exceeded tlle softening point of the frit by ahout 180 ~., but was about 280 F. belo~ the softening point of the glass articles to ~}liCh the enamel was appliecl. To si~ulate sand-blasting, a peak temperature range of about 1000-1100 F. is preferred.
In comparison to the smoothness to ~hich glass enamels are fired iJI applied color labeling, this enamel was incompletely fired. The firing cycle ~-as purposely set so low (and/or so short) that it did not permit the frit particles to fuse together as a smooth film, and they remained essentially as individual particles, but their contours l~ere rounded.
At 200 x magnification in a stereo microscope, the discrete particles appeared as irregular drops on a smootll surface, contacting one anotller at extremities but basically separate.
Under the microscope the appearance can be likened to elongated ~uic~isilver drops on a pla~e, or to a prin~ed circuit board.
The time and temperature of firing are to some extent interrelated, and the same rougll, non-continuous, non-glossy surface condition can be achieved with a shorter but higher temperature firing cycle, or with a lol~er temperature 31a~;~77~19 but lon~er firin~ cvele. In any event. }lowever. the time and temperature conditions must not be so severe as to cause the particles to coalesce entirely and flow out to form the glossy surface that is generally characteristic of an ACL type label.
The container was removed from the lehr after it llad cooled to about 250 F., tllen was remove(l and allowed to cool in air.
. .~, .
CO~IP~RISON TO SANDl'LAS~ED CONTAINER
To the unaided eye, the appearance of the container produced in the manner described in Example I very closely simulated that of a commercially marketed alcoholic beverage container witll a sandblasted surface.
I~'hen viewed microscopically the container treated by the new met]~od displayed the "discrete droplet" characteristic described above. Tlle sandblasted container on the other hand had an altogether different microscopic appearance. Its surface displayed the conchoidal depressiolls characteristic of flaked glass with highly irregular areas around tllem.
The sandblasted material showed pronounced streaking and spotting when water droplets l~ere sprinkled on it; this was far less apparent on the container produced by the new method. hloreover skin oil from the fingers would leave smudges or ingerprints on the sandblasted article which , .

lQ377~
the new article did not display. The sandblasted article left a whitish smear when rubbed against blue cloth, which the new article did not. Labelability of the new article was superior to that of the sandblasted article.
A standard oleic acid lubricity coating was applied to the new surface without affecting its appearance.
The same coating, when applied to the sandblasted container, -~
was immediately apparent, and would be detrimental in marketing.
EXAMPLÆ II
A similar container was coated in the same manner and with the same frit as in Example 1, but it was subjected to a more severe (higher) firing cycle, to produce a finer grained finish closely approximating an acid etched ,~j finish. The specific cycle used for that purpose is shown in -the drawing as the curve labeled B. The peak temperature used was 1160 F. (about 260 above the softening point of the frit, but still 200 below that of the glass container). To simulate etching a peak temperature of about 1125-1200 F. is preferred.
As a contrast, when another similarly coated container was fired at 1300 F., the firt formed a smooth surface bearing no resemblance to an etched or sandblasted surface. -It should be noted that application of the enamel as a wet spray (i.e., admixed with a liquid vehicle) -distinctly does not provide the same appearance. The wet -sprayed surface ; ~ . :

I ~377~18 . is excessively rougll and it does not effectively simulate san~-.. blasting. ~loreover, coating losses are hig}l and mask and chuck eleaning are dificult.
~ ~ Tlle new metllod has been described herein primarily .. in relation to coating of containers. ~rom this disclosure, those skilled in the art will recognize that its utility extends to a wide variety of other products, including light .. , bulbs, lamp globes, cosmetic containers, table ware, and other products on which a matte finish is desired.
~laving described the invelltion, what is claimed is:

, ~ ' , ''~ ,, ,

Claims (9)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. The method of coating a surface portion of a glass article comprising, preparing a glass enamel in dry powder form, said enamel comprising a particulate mixture of glass frit and a refractory inorganic pigment, said frit being of a high lead borosilicate glass, said enamel comprising about 80 to 99-1/2% wt.
frit and 20 to 1/2% wt. pigment, preheating the article to a temperature at which it is sufficiently electrically conductive to be coated by an electro-static dry powder spray, but which temperature is insufficient to thermally adhere particles of said enamel to the article, applying the enamel to the said surface portion by an electrostatic dry powder spray process wherein the said particles are carried by a mild air current from a spraying gun toward the said article, the said particles adhering to the surface portion by electrostatic attraction but not by thermal fusion, the enamel coating on said surface portion being ap-plied to deposit a layer thereon weighing about 0.0002 to 0.0006 oz./in.2, the temperature of said article being in the range of about 150-450°F. for said spraying, and firing the article and adherent glass enamel particles to a peak temperature which is about 50 to 300° F above the softening point of the frit to cause the particles to become fused to said surface portion as discrete droplets but in-sufficient to cause the particles to coalesce to form a smooth continuous film.
2. The method of Claim 1 wherein the firing is at a peak temperature of about 1000-1100° F., for a period of time such that the particles form a surface visually approximating a sandblasted surface.
3. The method of Claim 2 wherein said firing is at a peak temperature of about 1080° F.
4. The method of Claim 1 wherein the firing is at a peak temperature of about 1125-1200° F., for a period of time such that the particles form a surface visually approximating a chemically etched surface.
5. The method of Claim 4 wherein said firing is at a peak temperature of about 1160° F.
6. The method of Claim 1 wherein said glass enamel has the approximate composition:
7. The method of Claim 1 wherein said glass enamel in-cludes TiO2 pigment as a milled component.
8. The method of Claim 1 wherein the glass enamel is sub-stantially at room temperature until it contacts the glass article.
9. The method of Claim 1 further wherein, said glass article is a container having a closure receiving portion, a portion of said container is masked during said spray-ing by a mask which prevents the sprayed particles from contact-ing the masked portion of the container, sprayed particles adhering to the mask electrostatically but not thermally, and wherein the mask is removed from the container subse-quent to said spraying and the particles adhering to the mask are removed therefrom by an air jet.
CA199,619A 1973-05-14 1974-05-13 Electrostatic method of coating glass articles with a powder of glass enamel to simulate a sandblasted or etched appearance Expired CA1037788A (en)

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JP (1) JPS5069118A (en)
CA (1) CA1037788A (en)
DE (1) DE2423187A1 (en)
FR (1) FR2229659B1 (en)
GB (1) GB1465372A (en)

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4158080A (en) * 1978-10-10 1979-06-12 Corning Glass Works Glass enamel fluxes
US4343641A (en) * 1981-03-02 1982-08-10 Ball Corporation Article having a scratch resistant lubricated glass surface and its method of manufacture
EP0137354A3 (en) * 1983-10-06 1985-07-24 VEB Glaskunst Lauscha Process for making electrostatically coated glass objects
ES2081736B1 (en) * 1992-02-26 1996-10-01 Solvi Soluciones Del Vidrio S Procedure for Botelleria tempered glass and in general.
DE69607850D1 (en) * 1996-12-20 2000-05-25 Saga Decor Pont Sainte Maxence A process for producing a glass article for receiving a liquid
ES2154449T3 (en) * 1997-11-17 2001-04-01 Saga Decor Procedure for obtaining objects ornaments in glass packaging and decorated objects produced by this process
FR2825697B1 (en) * 2001-06-08 2004-05-28 Dmc2 France Degussa Metaux Cat email Powder destiny has to be applied on glass articles by electrostatic spraying of way to obtain after firing a frosted appearance similar to that obtained by acid attack
US20190192213A1 (en) * 2016-11-14 2019-06-27 Medtronic Advanced Energy Llc Colored vitreous enamel composition for electrosurgical tool

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1384158A (en) * 1962-12-04 1965-01-04 Owens Illinois Glass Co Method and apparatus for applying electrostatically an image printed on an object, particularly a glass article

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Publication number Publication date
CA1037788A1 (en)
JPS5069118A (en) 1975-06-09
GB1465372A (en) 1977-02-23
FR2229659B1 (en) 1977-10-28
DE2423187A1 (en) 1974-12-05
FR2229659A1 (en) 1974-12-13

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