US2174198A - Method of producing colored flatware - Google Patents

Description

Patented Sept. 26, 1939 Edward Schramm, Syracuse, N. Y., assignor to Onondaga Pottery Company, Syracuse, N. Y.,' a corporation of New York No Drawing. Application December 30, 1938,

Serial No. 248,579

'5 Claims. (01. 25-156) The general object of the present invention is to provide an improved-method of producing American vitreous china ware pieces, with their entire surfaces or large portions thereof orna- 5 mentally colored. The invention is of especial utility and value when used in the prduction of ornamentally colored American vitreous china' plates, saucers and other flat ware pieces.

The ceramic tableware identified and desig- 0 'nated herein, and not infrequently in the art, by

the term American vitreous china,- is a commercially important type of tableware, produced in large quantities in this country by manufacturing methods which have become standardized to the extent that theycomprise the following steps; namely, the shaping of each ware piece from plastic material of suitable composition, followed by drying, biscuit firing, glaze coating and glaze firing steps carried out in the order named. In lieu of shaping the pieces out of material in a plastic condition, the pieces may be formed by casting in water absorbing molds, into which the material and water mixture is poure'd -while in a fiuid condition. Usually the ware pieces, after their biscuit firing, and prior to being coated with glaze forming material, are sub- Jected to an abrasive, cleaning and surface smoothing treatment, and much of such ware is subjected to underglaze or overglaze decorative treatments.

The material from which American vitreous china is made, is one or another of various mixtures of clay, flint and fluxes such as feldspar, and calciumcarbonate in the form of whiting, the material when fused, slntering together to produce a vitreous non-absorbing body. The fusing and sintering occurs in the biscuit firing operation, which is ordinarily conducted-at a temperature of about 2250" F. In the su fi quentglaze firing operation, the ware pieces are heated to a temperature of about 2050 F. In its application to American vitreous china, the term vitreous" denotes a biscuit fired body condition of virtual non-absorptiveness throughout the body mass, which has such resistance to water absorption that the amount of water which the body can absorb is usually less than .5% of the dry weight of the body. Such vitreous body condition is due to and requires a 'body of suitable composition and its subjection to suitable processing and biscuit firing operations.

To prevent flatware pieces, such as plates and saucers, from sagging and distortion as they soften in the biscuit flring operation, the individual pieces are bedded or supported by pulverant non-fusible material, such ,as sand or clay. Ordinarily plates and saucers are assembled in stacks for the biscuit firing operation, and .the bedding operation involves the placing of the non-fusible bedding material between each two adjacent pieces in the stack. The capacity of the ware pieces to be thus bedded and supported during the biscuit firing operation without adhering to the refractory bedding' material, is a desirable characteristic, and contributes to the satisfactory and relatively inexpensive production of American vitreous china.

A specific object of the present invention, is to provides. method of producing colored chinaware of the type specified, in which the color, characteristic of the invention, is applied as an engobe to the surfaces of the ware pieces after'the latter have been shaped and dried, but prior to the ini-' tial or "biscuit" firing of the pieces, and in such manner as to permit the pieces to be bedded in stacks for biscuit firing, and'to be treated in the subsequent stages of the production of the finished 'ware, in accordance with the standard methods heretofore developed and used in the manufacture of vitreous china not so colored.

The colored engobe used in the practice of the present inventiorl, ordinarily comprises a base and color mixture, preferably applied in water color form, consisting of from 10% to 20% of color material in the form of a metallic pigment or pigment mixture and from to of a base material which is of such nature, in com bination with the added pigment, as to produce in the biscuit firing a vitreous layer, compatible in chemical and physical characteristics with the ware body to which it is applied and inseparably integrated therewith by fusion in the biscuit firing. It is understood that the proportions above mentioned are merely indicative and that, in obtaining the specified results, the practice of my invention is not limited to said proportions.

A further specific object of the invention, is to provide a method of manufacturing American vitreous china, in which the ornamental, surface coloring, material applied to the surfaces of the ware pieces prior to their first or biscuit firing,

' is of such character, and is applied in such manner, that the biscuit firing operation makes the colored coating portion of each ware piece vitreousin the same sense in which the body of the piece is vitreous. The physical structure of a ware piece colored in accordance with the present inventionis thus not significantly different from that of a similarly shaped ware piece which has undergone biscuit firing in the process of manufacture of vitreous china 'in the manner heretofore customary, and without the surface coloring characteristic of the present invention. Moreover, in consequence of the essential similarity in character of the colored slip and body materials, flatware pieces to which the colored slip has been applied may be bedded in stacks for biscuit firing in the manner customary in the production of uncolored American vitreous china, and soften, like the latter, during the biscuit firing operation, without attaining a glassy or sticky condition resulting in objectionable adherence of the bedding material to the ware.

Since ware colored in accordance with the present invention does not differ significantly in physical structure or character from uncolored American vitreous chinaware, ware pieces colored in accordance with the present invention may be treated like uncolored American vitreous chinaware pieces, not only in the biscuit firing operation, but in all manufacturing operations subsequent thereto. Thus biscuit fired ware produced in accordance with the present invention has such hardness and strength that it may be, and in a preferred practical form of the present invention is, cleaned and polished by a tumbling operation, carried out in a tumbling barrel or rotating container substantially filled with ware pieces and abrasive material of a granular nature. More over, ware pieces colored in accordance with the present invention may be subjected to any of the usual underglaze decorative treatments employed in the manufacture of uncolored American vitreous china. The vitreous condition of its colored coating portions facilitates the decorative treatment of the ware subsequent to its biscuit firing and prior to its glaze application, particularly when that treatment comprises the application of decalcomania. The vitreous condition of the colored coating portions of the biscuit fired ware also facilitates the production of ware having a glaze coating of fine quality.

The present invention possesses practically important advantages over the prior methods known to me, of producing American vitreous china ware pieces with their surfaces, or substantial portions thereof, ornamentally colored. The more usual prior methods involve the formation of the ware from colored bat or-body material, the underglaze application of the color to biscuit fired ware, and the overglaze application of the color to glaze fired ware. With a ware piece formed entirely from a' colored bat, it is not possible to obtain a suitably strong color in vitreous china-ware, without high expense because of the large amount of relatively expensive coloring material required. If colored and uncolored bats are pressed together to form a laminated ware piece, less color material is required than when the color is distributed throughout the entire body of the piece, but color cost is still greater than with the present invention, and the laminated articles are difficult to make.

The surface of vitreous china ware can be covered, in whole, or in part, by a color layer applied on the biscuit fired ware prior to the glazing. However, with that process, it is difficult, if the area colored be large, to secure uniformity of color. Furthermore, it ,is practically impossible to impose ordinary underglaze decorative treatments on the surface portions of the biscuit fired ware to which the color layer hasbeen applied, unless after the color layer application, the ware is subjected to a special firing operation, preceding the regular glaze firing operation. As previously explained, ordinary underglaze decorative treatments can be applied to biscuit fired ware to which color has been applied in accordance with the present invention, with substantially the same freedom and ease as they can be applied to uncolored biscuit fired ware.

The overglaze application of the coloring agent involves a third firing of the were in a decorating kiln at a temperature of about 1350 F., and necessarily results in a relatively high cost of production. Furthermore, the overglaze color application, like the usual overglaze decorative effects, rubs of! or wears away in time.

Color applied to ware in accordance with the present invention does not wear or rub of! because it is protected by the glaze, which is not affected by the color, and like the glaze coatin of ordinary uncolored American vitreous china, is transparent, strong and wear-resistant.

Color effects have also been obtained by using colored glazes, but this method has distinct limitations, especially as applied to American vitreous china, due chiefly to the difficulty of applying the coloredgla'ze with uniformity on a virtually non-absorbent body, and to the fact that the coloring matter in the glaze may adversely affect properties of the finished glaze, and to the further fact that colored glazes necessarily tend to mask underglaze decorative treatment effects.

In another known method of obtaining colored ware, first a colored engobe and then a coating of transparent colorless glaze forming materials, are applied to the dried but unfired ware, after which the latter is subjected to one fire operation simultaneously affecting the body, engobe, and glaze. The use of this method is limited by the difficulty often involved in the application to the unfired ware of the two coatings-the engobe and the glaze-and the method is not usable in the production of fiat ware pieces which must be em-- bedded in refractory material for the biscuit firing operation, as the bedding or supporting material would adhere to the glaze surface. Another disadvantage of the last mentioned method, is that desirable decorative treatments such as commonly are used in the chinaware industry, cannot be readily applied to ware so treated prior to its firing.

A very important feature of the present invention is the practical application of one decorative color treatment superimposed on another decorative color treatment, at reasonable cost. Heretofore this has been practical as applied to the manufacture of American vitreous chinaware,

only by the use of methods involving either pigmented bodies, overglaze decorations, or base layers of color applied on the biscuit fired ware, which layers must be given an additionalfiring to fuse the color, before applying another color treatment thereon. The objections to the first two methods mentioned, have been made clear above. The objection to the last mentioned method is, of course, the added expense of the additional firing which it requires. The present invention makes practical, and at reasonable expense, an unlimited number of desirable combinations of colored decorative treatments, one superimposed on the other, and all applied underglaze, thereby being protected by the glaze from wearing of! in service.

A preferred and inexpensive method of carryis to use a guard .of suitable material and contour to cover that portion of the ware piece which is to be left in the natural body color, and then to apply the colored engobe to the balance of the piece by spraying the engobe thereon by an fair b I The invention has certain practicallydesirable characteristics not. previouslyv mentioned. For one thing, it permits proper protection of delicate colors. In the usual method of applying underglaze color to biscuit fired wares, certain colors, notably, delicate pinks, yellows and light greens, are of such nature that there is a tendency to their destruction by the action of the glaze in the glost firing operation, and a tendency for such 'colors to come from the glost firing kiln with nonuniform color values. With the present invention, delicate colors can be immutably fixed in the biscuit firing operation, so as not to be subject to alteration in the subsequent glost firing.

The invention permits of new color combinations in that it is readily practical to combine the use of an engobe of any desired color' applied in accordance with the present invention with the use of certain regular underglaze colors which require the subsequently applied glaze materials to be of a special character suitable for the protection and development of the particular underglaze colors employed, and not suitable for certain other such colors, since, in general, the engobe color is not adversely affected by the use of the special glaze materials required to protect sible with the invention to obtain brilliant reddish browns, in conjunction with delicate pink and green underglaze decorative effects.

' Q Having now described my invention, what I claim as new and Patent, isz' 1. The method of producing surface colored American. vitreous china warewhich consists in shaping said ware froin'body, material in a moist condition and of such composition as to be fused and sintered by a biscuit firing operation into a hard vitreous body characteristic of American vitreous chinaware, drying the shaped ware and thereafter coatingthe ware surface to be colored with an engobe comprising a pigmented material, biscuit firing the coated ware, said pigmented material being of such composition that it is fused and sintered by the biscuit firing operation into a colored surface portion of the ware in permanent adherence, and similar inhardness and in its vitreous character, to said fused and sintered body, coating the biscuit fired ware with glaze forming material, and then'glaze firing desire to secure by Letters and develop the said regular. underglaze decorative'color applications. For example, it is pos-,

a surface.

the ware at a temperature below the biscuit firing temperature.

2. The method of producing surface colored American vitreous china ware which consists in shaping said ware from body, material in a moist condition and of such composition as to befused and sintered by a biscuit firing operation into a hard vitreous body characteristic of American vitreous chinaware, drying the shaped ware and thereafter coating the ware surface to be colored with an engobe comprising a pigmented material,

biscuit firing the coated ware, said pigmented material being of such composition that it is fused and sintered by the biscuit firing operation into a colored surface portion of the ware in permanent adherence, and similar in hardness and in its vitreous character, to said fused and'sintered body, applying, a decorative design to the engobe treated surface of the biscuit fired ware, then coating the ware with glaze forming material and then glaze firing the ware at a temperature below the biscuit firing temperature.

3. The method of producing surface colored American vitreous china flatware pieces, which consists inshaping said pieces from body material in a moist condition and of such composition as to be fused and sintered by a biscuit firing operation into a hard vitreous body character-' istic of American vitreous chinaware, dryingv said pieces and thereafter coating the surfaces to be colored with anengobe comprising a pigmented material, and further drying-the ware pieces, bedding the ware pieces in stacks with pulverant non-fusible material interposed between adjacent pieces in the stack, biscuit firing the bedded stacks,said engobe being of such composition that it is fused and sintered by the biscuit firing operation into ,a colored surface portion of the ware integrally connected with,

and similar in hardness and in its vitreous character to said fused and sintered body, without gobe covered portions of the surfaces of the biscuit fired ware pieces prior to coating said pieces with glaze forming material.

5. The method specified in claim 1, in which, prior to being coated with the glaze forming material, the biscuit fired ware pieces are cleaned and polished by. a tumbling action and decorative designs are superimposed on the engobe covered portion of the cleanedand polished ware