Process for vitreous enamel coating

Those skilled in the enameling art have tried for years to produce multi-colored articles wherein the colors are overlapping or adjacent to each other by vitreous enamel coating and in a single firing operation, however, the best that has been accomplished before my invention is the production of articles which may have more than one color thereon, provided that such colors do not touch each other, or provided they are not overlapping or superimposed one on the other. .As heretofore practiced, the manufacture of multi-colored vitreous enameled articles has been carried out by a separate firing for each color when it is necessary to overlap or superimpose one color upon another. In the manner in which the colors have been applied in the past, if separate firings are not accomplished, then the finished article will be full of blisters and enamel defects and if separate firings are accomplished the finish will not be uniform, but will be stepped up, each subsequent color coating being higher than the last. Also every time a color coat is fired the color fades out so that the first color applied has changed to an undesirable shade after repeated firings and the colors lose the desired brilliance. Furthermore, there is a limit to the number of firings to which the first coat applied can be subjected, so that the prior process has serious limitations.

In the enameling art, as heretofore practiced, coatings averaged about 1% ounces per square foot of surface, (dry weight); some coatings may run as low as 1 ounce or may go as high as 1% ounces per square foot. The vitreous enamel coating in the present practice should pass through a 40 to 60 mesh screen and in some cases, such as for silk screen work, they are put through a screen as fine as 200 mesh.

A further object of my invention is to produce a multi-colored vitreous enameled article, or one having different hues, shades and different color tone in one firing and having a substantially smooth surface thereon free from blisters and blowholes and other enamel defects.

Another object of my invention is to reproduce vitreous enameled products of various colors, which may be superimposed, one upon the other, by a printing press. My invention generally comprises a wet enameling process wherein I start with a. metal base upon which one ground coat and one or two cover coats of enamel have been applied, this ground coat being a vitreous enamel coating 16 fused to the metal base. I then may apply a fine “wash coating” of frit over the surface to which other colors are to be applied; this wash coating may contain some coloring matter or it may be white. In the wash coating just referred to and in subsequent frits and colors applied to the article thereafter, the particles in the frit and coloring matter may be, and preferably are, of a size to belong to the class of dispersoids; that is, the solution is such that the particles range in size from 0.1 micron to one milli-micron, a micron being equal to .00003937 inch.

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