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To Clean Alabaster

Soap well and wash with hot water. If stained, apply fuller's earth, pipe-clay, or whiting, for 3 or 4 hours, then wash off. If very dirty and stained, first wash with aquafortis diluted with water. Or: Take ground pumice stone of the finest quality, and mix it up with verjuice; let it stand for 2 hours, then dip in a sponge and rub the alabaster with it; wash with a linen cloth and fresh water, and dry with clean linen rags. Any kind of marble may be done in the same manner. 2035. Το Polish Marble. With a piece of very fine sandstone, rub the slab 2028. To Harden Plaster with Sulphate of Potassa. If equal parts of common calcined plaster of Paris and of sulphate of potassa be mixed together, they will harden backward and forward, using very fine sand in a moment with less than an equivalent and water, till the marble appears equally weight of water; so much so, indeed, that the mixture cannot be poured out of the vessel.

If, however, 1 part of each of the salts and 2 of water be used, they form a mass which cannot be poured out, and the surface of which will be found coated with a crust of sulphate of potash. The rapidity of hardening, therefore, can be made to vary with the percentage of water, the mass solidifying even if 6 parts of water be used.