The block which serves to apply the adhesive basis of the velvet-powders, bears in relief only the pattern corresponding to that basis, which is formed with linseed oil, rendered drying by being boiled with litharge, and afterwards ground up with white lead. The French workmen call this mordant the encaustic. It is put upon the cloth which covers the inverted swimming tub, in the same way as the common colours are, and is spread with a brush by the tireur (corruptly styled tearer by some English writers). The workman daubs the blocks upon the mordant, spreads the pigment even with a kind of brush, and then applies it by impression to the paper. Whenever a sufficient surface of the paper has been thus covered, the child draws it along into the great chest, sprinkling the flock powder over it with his hands; and when a length of 7 feet is printed, he covers it up within the drum, and beats upon the calf-skin bottom with a couple of rods to raise a cloud of flock inside, and to make it cover the prepared portion of the paper uniformly. He now lifts the lid of the chest, inverts the paper, and beats its back lightly, in order to detach all the loose particles of the woolly powder.
By the operation just described, the velvet-down being applied every where of the same colour, would not be agreeable to the eye, if shades could not be introduced to relieve the pattern. To give the effect of drapery, for example, the appearance of folds must be introduced. For this purpose, when the piece is perfectly dry, the workman stretches it upon his table, and by the guidance of the pins in his blocks, he applies to the flock surface a colour in distemper, of a deep tint, suited to the intended shades, so that he dyes the wool in its place. Light shades are produced by applying some of his lighter water-colours.
Gold leaf is applied upon the above mordant, when nearly dry; which then forms a proper gold size; and the same method of application is resorted to, as for the ordinary gilding of wood. When the size has become perfectly hard, the superfluous gold leaf is brushed off with a dossil of cotton wool or fine linen.
The colours used by the paper-hangers are the following:—
1. Whites. These are either white-lead, good whitening, or a mixture of the two.
2. Yellows. These are frequently vegetable extracts; as those of weld, or of Avignon or Persian berries, and are made by boiling the substances with water. Chrome yellow is also frequently used, as well as the terra di Sienna and yellow ochre.
3. Reds are almost exclusively decoctions of Brazil wood.
4. Blues are either prussian blue, or blue verditer.
5. Greens, are Scheele’s green, a combination of arsenious acid, and oxide of copper; the green of Schweinfurth, or green verditer; as also a mixture of blues and yellows.
6. Violets are produced by a mixture of blue and red in various proportions, or they may be obtained directly by mixing a decoction of logwood with alum.