and other
stones
are coloured, and the stain is required to be deep, it should be poured on boiling hot, and brushed equally over every part, if made with water; if with spirit, it should be applied cold, otherwise the evaporation, being too rapid, would leave the colouring matter on the surface, without any, or very little, being able to penetrate. In greyish or brownish stones, the stain will be wanting in brightness, because the natural colour combines with the stain; therefore, if the stone be a pure colour, the result will be a combination of the colour and stain.
In staining
bone
or
ivory
, the colours will take better before than after polishing; and if any dark spots appear, they should be rubbed with chalk, and the article dyed again, to produce uniformity of shade. On removal from the boiling hot dye-bath, the bone should be immediately plunged into cold water, to prevent cracks from the heat.
If
paper