The method heretofore known for engraving on glass, has been by means of a machine with wheels, of different substances, which have been employed with sand, etc., to grind off some parts of the surface of the glass which is to be engraved on, and then by means of grinding and polishing different parts on the rough surface, the different figures are formed according to the designs given. By this invention, instead of grinding or taking off any part of the surface of the glass, the patentee lays on an additional surface or coating of glass, prepared for the purpose, which, when subjected to a proper degree of heat, will incorporate with the glass to be operated upon, so as to produce an effect similar to that which has hitherto been obtained by means of grinding. When it is required to ornament glass, then, previously to the heat being applied, with an etching or engraving tool such parts are to be taken out as will produce the required effect, and that in a much superior way to the effect produced by the usual mode of grinding, polishing, etc. The materials used are to be melted in a crucible, or other pot, and they are to be made up in the same manner as if used for the making of the best flintglass, broken glass, or, as it is usually denominated, "cullitt", being the principal ingredient in it. Several mixtures are given, of which the first is 160 parts of cullitt, 10 of pearlash, 40 of red-lead, and 10 of arrence.
The second is 120 parts of cullitt, 160 of red-lead, 60 of sand, and 60 of borax.
The third is 70 parts of red-lead, 22 1/2 of sand, and 410 of calcined borax.
When these are subjected to such a heat as to be thereby completely fused, take equal parts of each mixture and grind them to an impalpable powder, for the purpose of being mixed with a menstruum proper for coating the glass.
The menstruum consists of 1 part of refined loaf sugar dissolved in 2 parts of pure water, to which is added, at the time of mixing the powder, about 1/3 part of common writingink; the effect, we are told, produced by this addition of oxide of manganese, used in a small quantity by the glassmakers in making their best flint-glass, because without such an addition the specimens would be of a cloudy or milky appearance. A quantity of this menstruum is used sufficient to render the ground-mixture of a proper consistence for laying on with a thin, smooth surface. When the coating or mixture is thus prepared, the glass is to be coated by means of a camel's-hair brush, or squirrel's-foot, etc. It is then to be exposed to a heat sufficient to produce a semivitrification of the coaty surface, and to incorporate it with the substance or body of glass so coated. But the heat must not be carried higher than this, because in that case a complete vitrification would ensue, and the desired effect of having a surface in imitation of the rough surface produced by grinding would not be obtained; the article must, under such circumstances, be re-coated and submitted again to the fire. If, after the coating has been applied, any borders, cyphers, or other ornaments, are wanted to be executed thereon, then, previously to the heat being applied with an etching or engraving tool, such parts of the coated surface must be chased out as will produce the desired effect, after which the requisite degree of heat is to be applied.
This invention is not only applicable to all kinds of useful and ornamental articles of glassware on which the common methods of engraving have been practised, but may be applied to window-glass and plate-glass of every description, in place of grinding for the purpose of making window-blinds. It is also said to be peculiarly adapted to produce beautiful specimens of art for the windows of altar-pieces, libraries, museums, coach-windows, and for the glass used in ornamental buildings of all descriptions. This invention has another advantage over the common method of the work wearing much cleaner than the work of ground glass, the surface of which being fractured by the action of the wheel, etc., is therefore liable to gather dirt on the rough, unpolished parts of the borders, etc.
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