254. Cement and Ground Glass Imitation.—In half-a-pint spirits of wine steep one ounce of isinglass twenty-four hours, then dissolve it over a slow fire, keeping the vessel covered that the spirit may not evaporate (for this purpose a double saucepan should be used, the outer one containing water, after the manner of a glue-pot; or the solution may be made in a jar with a lid, tied over also with bladder, and placed in a saucepan of water—the water should surround the jar to the height of two inches or more, but not so high as to float it). When the isinglass is completely dissolved, add the juice of garlic, obtained by pounding in a mortar six cloves of the root, and straining through linen. Mix well, and cork close for a short time. The mixture will then cement either glass or crystal.
254a. Cement to resist Fire and Water.—Half-a-pint each of vinegar and milk, simmer them together till the curd separates. Strain, and with the whey mix the whites of five eggs well beaten up. The mixture of these two substances being complete, add sifted quick-lime, and make the whole into the consistence of putty. Let it be carefully applied—that is, to lay it on every part of the broken edges, and to make the edges fit exactly; as soon as it is perfectly dry, it will be found to resist both heat and moisture. Whatever the article was originally calculated to bear, it is again fitted to bear as much as if it had never been broken.
255. To imitate Ground Glass.—Rub the glass over with a lump of glaziers' putty, carefully and uniformly until the surface is equally covered. This is an excellent imitation of ground glass, and is not injured by rain or damp. It is useful for kitchen windows, &c.
256. To cement Broken China.—Mix some oyster-shell powder with the white of a fresh egg, to the thickness of white paint, lay it on thick at the two edges and join them as exact and quick as possible, then put it before the fire till the china is quite hot, and it will cement in about two minutes. Pour boiling water into it directly, wipe it dry, scrape it clean on both sides with a penknife, and it will appear only as a crack. Mix no more than you can use for one or two things at a time; for if the cement grows hard, it will be spoiled. The powder may be bought at the apothecaries'; but it is best prepared at home, which is done as follows:—Choose a large, deep oyster-shell; put it in the middle of a clear fire till red-hot, then take it out and scrape away the black parts; pound the rest in a mortar as fine as possible; sift and beat it a second time, till quite smooth and fine.
257. Obs.—In cementing china and glass, first heat the portions, and when the cement is applied, press them closely together, as the thinner the cement is, the more firmly it holds.