A thin paste made of one of the graining powders and water is spread by means of a spatula upon the watch parts held upon the cork. The cork itself is placed upon an earthenware dish, to which a rotating movement is imparted by the left hand. An oval brush with close bristles, held in the right hand, rubs the watch parts in every direction, but always with a rotary motion. A new quantity of the paste is added two or three times, and rubbed in the manner indicated. The more the brush and the cork are turned the rounder becomes the grain, which is a good quality; and the more paste added the larger the grain. When the desired grain is obtained, the pieces are washed and then scratch-brushed. The wire brushes employed, which usually come from Nuremberg, are made of brass wires as fine as hair, very stiff and springy. It is necessary to anneal them upon an even fire to different degrees; one soft, or half annealed, for the first operation or uncovering the grain; one harder, for bringing up the lustre; and one very soft, or fully annealed, used before gilding for removing any marks which may have been made by the preceding tool, and for scratch-brushing after the gilding, which, like the graining, must be done by giving a rotary motion to the tool.
Decoctions of liquorice or saponaire are employed in this operation.
(6) Silver powder, 1 oz.; cream of tartar, 4-5 oz.; common salt, white and clean, 13 oz.
(c) Silver powder, 1 oz.; cream or tartar, 3 oz.; common salt, white and clean, 2 lb.
All these substances should be as pure as possible, and perfectly dry. Cream of tartar is generally dry common salt often needs, before or after it has been pulverised, a thorough drying in a porcelain dish, in which it is kept stirred with a glass rod. The mixture of the three substances must be thorough, and effected at a moderate and protracted heat. The graining is the coarser the more common salt there is in the mixture; and it is the finer and more condensed as the proportion of cream of tartar is greater, but it is then more difficult to scratch-brush.
(a) If it happens that the same watch part is composed of copper and steel, this latter metal requires to be preserved against the action of the cleansing acids and of the graining mixture, by a composition called resist. This consists in covering the pinions and other steel parts with a fatty composition, which is sufficiently hard to resist the tearing action of the bristle and wire brushes, and insoluble in the alkalies of the gilding bath. Yellow wax, 2 oz.; translucent colophony, 3 1/3 oz.; extra fine red sealing-wax, 1 1/3 oz.; impalpable iron peroxide or polishing rouge, 1 oz. Melt the colophony and sealing-wax in a porcelain dish upon a water bath, and afterwards- add the yellow wax. When the whole is thoroughly fluid, gradually add the rouge, and stir with a wooden or glass rod. Withdraw the heat, but continue the stirring until the mixture becomes solid, otherwise all the iron oxide will fall to the bottom of the mixture. The flat parts to receive this resist are slightly heated, and then covered with the mixture, which melts and is easily spread. For covering steel pinions, employ a small gouge of copper or brass fixed to a wooden handle. The metallic part of the gouge is heated upon- an alcohol lamp, and a small quantity of resist is taken with it.
The composition soon melts,, and, by turning the tool around the steel pinion, this becomes coated. Use a scratch-brush with long wires, as their flexibility prevents the removal of the composition. When the resist is to be removed after gilding, place the parts in warm oil or tepid turpentine, then in a very hot soap-water or alkaline solution, and, lastly, in. fresh water. Scratch-brush and dry in warm saw-dust of white wood. The holes of the pinions are cleaned and polished with small pieces of very soft white wood, the friction of which is sufficient to restore the primitive lustre. The gilding of parts composed of copper and steel requires the greatest care, as the slightest rust _ destroys their future usefulness. Should some gold deposit upon the steel, it should be removed by rubbing with a piece of wood and impalpable pumice-dust, tin putty, or rouge.
(b) When it is desired to obtain gildings of several colours upon the same object, resists, generally made of some kind of varnish, are used. After having gilt an article of a uniform red or green colour, it is covered with a fat varnish, made drying by the addition of lead chrornate, at those places which are to resist the action of the new bath. By means of resists and successive baths, several different shades can be obtained upon the same object. The resist varnishes are applied with a brush or pencil, and should be thoroughly dried in a stove before placing the object in another solution. These varnishes may be coloured with various oxides or coloured salts, in order to facilitate their use upon those places which should be sharply marked; lead chromate and artificial ultramarine blue are well suited for the purpose. Resist varnishes are also used for preserving the reverse parts of articles which have to receive the -gilding only on the front. When the operation is finished, the resist is easily removed by washing, first with essence of .turpentine, gasoline, benzine, or benzole, and then with alcohol; when benzole is used, it is sufficient to wash the article in boiling water, and then to dry it in warm sawdust of fir-wood. It comes out perfectly clean.
This is not always the case with rectified turpentine, and it may be necessary to plunge the object into a hot alkaline lye, then to rinse and dry it in warm saw-dust.