POLYCHROME MOSAIC
FIG. 32.—POLISHING MOSAIC
This style of decoration consists of different coloured leathers arranged upon a ground, and is the only one that can properly be called leather mosaic. The work of marking it out is a lengthy one and demands scrupulous exactitude. A finished design is first painted in water-colours and marked with letters which are repeated on
the pieces of coloured leather, so that the exact place is indicated which they are to occupy in the design. It is important in this style of mosaic to obtain a very correct tracing of the design on the groundwork. On a smooth and light ground the tracing-point lightly worked will be sufficient; when the ground is dark or has a grained surface, red or white transfer paper should be used. The most satisfactory method of marking the design is by impressing a stencil of thick paper, but it cannot be employed with morocco leather for fear of crushing the grain too much. A thick stencil, however, carefully used without exerting great pressure, may give a sufficient result without spoiling the grain.
For polychrome mosaic on a smooth ground with an inlay of split sheepskin pasted on Canson paper, the method already described for working mosaic of one colour is the best, but at the same time the directions which are given below for placing the differently coloured skins side by side in position should be followed.
POLYCHROME MOSAIC ON A MOROCCO GROUNDWORK
Morocco leather for inlaying is thinned with the paring-knife, but it cannot be reduced to the excessive thinness of split sheepskin. It possesses, however, the advantage that the extreme edges may be made thinner in proportion for laying one over the other at the point where they meet.
After it is pared, the back of the leather is pasted over and it is pinned out on a board to dry. The different parts of the design to be inlaid are then traced on the various coloured leathers, and cut out in the manner already explained. The difficulty of placing the pieces exactly edge to edge is so great that it is better to allow them to overlap very slightly, but in order that this should not produce undue thickness at the point where they join, the substance of the extreme edges must be further