263. Blood Cement.—Blood Cement, for repairing copper boilers, &c., is made by pounded quick-lime and ox-blood mixed together: it must be applied fresh made, as it soon becomes so hard as to be unfit for use.
264. Diamond Cement.—Diamond Cement, for glass or china, is made by dissolving a quarter of an ounce of isinglass in water, by boiling it to the consistence of cream. Add a table-spoonful of spirits of wine. Use warm.
265. Cement for attaching Metal to Glass or Porcelain.—Take two ounces of a thick solution of glue, and mix with one ounce of linseed oil varnish, or three-quarters of an ounce of Venice turpentine. Boil together, agitating them until thoroughly mixed. The pieces to be cemented should be left untouched, after having been united, for forty-eight or sixty hours.
266. To mend Tortoise-Shell.—To mend tortoise-shell, bring the edges of the pieces to fit each other, observing to give the same inclination of grain to each; then secure them in a piece of paper, and place them between hot irons or pincers; apply pressure, and let them cool. Take care that the heat is not too great, or it will burn the shell.
267. To clean Gold Chains, &c.—Make a lather of soap and water; boil the chain in it for a few minutes, and immediately on taking it out, lay it in magnesia powder which has been heated by the fire; when dry, rub it with flannel; if embossed, use a brush.