Imitating marble.

Scientific American 11, 10.9.1859

Variegated marble may be imitated in all the rich colored veins for which some species of it are distinguished. For this purpose a polished block of marble to be treated is first warmed in an appropriate oven to open its pores, after which the colors are applied. These consist of an alcoholic solution of alkanet root, to produce a rich lavender, a madder lake to make a crimson, indigo to produce a blue, verdigris green and gamboge yellow. They are put on according to the fancy and taste of the artist, so as to form the desired pattern, after which the marble is again raised in temperature to make it absorb the colors, then cooled gradually and afterwards rubbed down to a smooth face with pumice stone and water. The principle of operation is similar to that of staining wood to imitate the rich qualities of mahogany, walnut, satin and rosewood.