This section is from the book "The Tinman's Manual And Builder's And Mechanic's Handbook", by Isaac Ridler Butt. Also available from Amazon: The Tinman's Manual And Builder's And Mechanic's Handbook.
This species of work is exquisitely beautiful when done with taste and judgment, and is so like marble to the touch, as well as appearance, that it is scarcely possible to distinguish the one from the other. We shall endeavor to explain its composition, and the manner in which it is applied; but so much depends upon the workman's execution, that it is impossible for any one to succeed in an attempt to work with it without some practical experience.
Procure some of the purest gypsum, and calcine it until the large masses have lost the brilliant, sparkling appearance by which they are characterized, and the whole mass appears uniformly opaque. This calcined gypsum is reduced to powder, and passed through a very fine sieve, and mixed up, as it is wanted for use, with glue, isinglass, or some other material of the same kind. This solution is colored with the tint required for the seagliola; but when a marble of various colors is to be imitated, the several colored compositions required by the artist must be placed in separate vessels, and they are then mingled together in nearly the same manner that the painter mixes his color on the pallet. Having the wall or column prepared with rough plaster, it is covered with the composition, and the colors intended to imitate the marble, of whatever kind it may be, are applied when the floating is going on.
It now only remains to polish the work, which, as soon as the composition is hard enough, is done by rubbing it with pumice-stone, the work being kept wet with water applied by a sponge. It is then polished with Tripoli and charcoal, with a piece of fine linen, and finished with a piece of felt, dipped in a mixture of oil and Tripoli, and afterwards with pure oil.