There are many cements for repairing china and porcelain. For large articles, plaster-of-Paris worked up with alum solution may be used; or plaster-of-Paris may be stirred into a clear solution of gum arabic. This should be used immediately, but is useless if the vessel to be mended has to hold water. A cement which is said to stand both heat and water is made by calcining and grinding oyster shells. These are then reduced to the finest powder possible with a muller, and the whole is beaten into a paste with white of egg. In using this preparation the broken parts should be pressed well together. A good cement for repairing broken glass is made by placing in a wide-mouthed bottle a small quantity of glue, just covering it with water, and allowing it to stand over-night; next day the excess of water is poured off and the glue is covered with methylated spirit. The bottle is then placed in a pan of water and heated until the glue is melted, then a little whiting is shaken into it, the bottle removed from the pan, cooled, and tightly corked. Sometimes a small piece of gum mastic, together with some ammoniacum, is added to such cements. Another useful cement for the purpose can be made as follows.

Cover 4 oz. of gelatine with strong acetic acid, and, after standing, melt it down by placing the bottle in hot water. Both these cements are ready for use if they are placed for a few minutes in hot water. Another cement for glass, etc., is made by coagulating milk with acetic acid and washing the casein in water. It is then dissolved in a cold saturated solution of borax, and a clear solution obtained, which is mixed with finely powdered quicklime. This should be applied to the broken parts quickly, and the whole bound tightly with cord and gently heated. A sulphur paste for porcelain is made with sulphur, 7 parts; white pitch, 5 parts; bleached shellac, 1 part; glass meal, 7 parts; gum elemi,2 parts; and mastic, 2 parts. Avery strong solution for glass or porcelain may be obtained from casein dissolved in a soluble silicate of soda or potassium. To prepare pure casein, skim the milk of all cream and stand it in a warm place till it curdles. It should then be filtered, washed with water, tied in a. cloth, and boiled in water. It should be allowed to dry on blotting-paper, and can then be kept for a long time.

A waterproof cement for attaching glass to wood, slate, etc., is made by mixing together litharge, 3 parts (by measure); white lead, 3 parts; plastr-of-Paris, 3 parts and powdered resin, 1 part. Make into a paste with boiled linseed oil, and use at once. For a transparent cement, boil isinglass in spirit of wine. A cement to repair porcelain or glass and to withstand heat is made by rubbing up in a mortar white of egg and a little dry lime. Paint this on the broken edges, put the article together, then paint strips of calico with the mixture and lay them over the broken parts outside, and allow to stand for several days. A coat of oil paint could then be put on, and would render the whole waterproof. Silicate of soda or potash (commonly known as water glass) sticks well to glass, and will stand heat. Either of these, however, attacks and slightly roughens the glass. Another heat-resisting cement for glass is the following. Pulverise together in a mortar 1/2oz. of powdered glass and 1 oz. of fluorspar until they are reduced to an impalpable powder, then mix with 3oz. of silicate of soda and work it into a smooth paste, which sets very rapidly. A reliable cement for repairing glass and china goods is a saturated solution of isinglass in pyroligneous acid.

With the following cement, the article is required to dry slowly in a warm place: 10 parts of white lead and 6 parts-of pipeclay, carefully dried, are incorporated with 5parts of boiled linseed oil, heated on a water-bath. To repair a broken washhand basin, cover the outside of the parts to be joined with ordinary oil paint, then lay on a strip of calico, or thin canvas, and paint that outside. This is not very neat, but such a patch lasts for years. A solution of 8oz. strong glue and 3/4oz. Venice turpentine, boiled and well stirred together, will unite glass and metal. To join glass to wood, make a cement by melting loz. beeswax with 1 oz. resin, and stirring into it 1 oz. Venetian red. Use whilst hot, and warm the glass. If the wood is to join the edge of the glass, a groove in the wood will assist in holding it. Roughening the surface of the glass where the join is with emery powder will also help the cement to stick. In cementing white enamel or glass letters on windows, first dust French chalk over the glass, then coat the back of the letters to about 1/8 in. with white lead and japanners' gold size, which should have been mixed together twelve hours before. Press the letters well down, and clean the cement from the edges with a chisel knife.

Another cement for the purpose, and one which dries quickly, may be made by mixing together 1 part white lead, 2 parts litharge, 3 parts boiled linseed oil, and 1 part copal varnish. The following cement has been recommended for uniting china to metal. Melt resin 20 paints, and stir in plaster-of-Paris 2 parts, and boiled linseed oil 1 part. If kept in a closed bottle, this cement may be used at any time by simply heating it.