cements, casein - Cements, Casein; cements, casein - Casein or cheese has long been used for forming cements, either in combination with quicklime, borax, or, more recently, with silicate of soda. The most important point that requires attention, in order to secure success, is the freeing of the casein from all oily matter. Therefore, when curd is prepared from milk, use only the most carefully skimmed milk, quite free from cream. When cheese is used, select the poorest, and wash it carefully.
Skim-milk cheese, cut in slices, and boiled in water. Wash it in cold water, and knead it in warm water several times. Place it warm on a levigating stone, and knead it with quicklime. It will join marble, stone, or earthenware, so that the joining is scarcely to be discovered.
Casein, dissolved in soluble silicate of soda or potash, makes a very strong cement for glass or porcelain. Take casein, free from fat, and wash until no longer acid, and silicate of soda solution (waterglass) of each as much as may be needed. Fill a bottle to J of its height with damp casein; then fill the flask with silicate of soda (waterglass), and shake frequently until the casein is dissolved.
Take the curd of skim milk (carefully freed from cream or oil), wash it thoroughly, and dissolve it to saturation in cold concentrated solution of borax. This mucilage keeps well, and, as regards adhesive power, far surpasses the mucilage of gum arabic. It forms a valuable preparation for the laboratory, as when spread on strips of bladder it may be used to stop cracks in glass vessels, and will resist considerable heat.
Add ½ pint of vinegar to ½ pint skimmed milk; when the curd has settled, pour off the liquid, and wash the curd until free from acid. Add the whites of 5 eggs and beat thoroughly; mix with sufficient finely powdered quicklime to form a paste. This is an excellent cement for mending glass and earthenware. It resists water and a moderate degree of heat.
The chief cement used in the island of Sumatra is made from the curd of buffalo milk, prepared in the following way. The milk is left to stand till all the butter has collected at the top. The latter is then removed and the thick sour mass left is termed the curd. This is squeezed into cakes and left to dry, by which it becomes as hard as flint. For use, some is scraped off, mixed with quicklime, and moistened with milk. It holds exceedingly well, even in a hot damp climate, and is admirably adapted for mending porcelain vessels.
In the German cantons of Switzerland, a compound of cheese and slaked lime is used, under the name of Tcaseleim, for laying floors, puttying joiners' work, making blocks for hand-printing cotton and tapestry goods, and other like purposes. The material sets so rapidly, that it is necessary to mix it as the work goes on, which entails trouble and necessitates a certain knack in its use. A Swiss chemist, Brunnschweiler, of St. Gall, has invented a preparation of lime and skim-milk, to which he gives the name of Kaseleim-pulver, whereby these inconveniences are avoided. It is a very fine, dry powder, which keeps well, and for use only requires mixing with water, when it displays all the properties of ordinary quicklime. It sets quickly, and hardens with age. Professor Gintl, of Vienna, reports most favourably of the preparation.
By heating milk with a little tartaric acid, the casein is coagulated. This casein is then treated with a solution containing six parts of borax, to one hundred parts of water and warmed. It speedily dissolves and forms a very tenacious, durable, and inexpensive adhesive medium.