Put milk in a cool place, and after taking off the cream as long as any is formed, remove the skimmed milk to a warm place to coagulate. After heating the curd, place it upon a filter and wash the caseine remaining upon the filter with rainwater until the water running off shows no trace of acid.
To remove the last traces of fat tie the washed caseine in a cloth and after boiling it in water, spread it upon blotting paper in a warm place to dry. It will shrivel up to a horny mass.
When thoroughly dried pure caseine will keep for a long time without suffering alteration. To obtain the caseine in a form suitable for preparing cements it is only necessary to pour water over a corresponding quantity and allow it to stand for some time. Caseine combines with lime to a hard insoluble mass.
Ordinary technical caseine may be readily and cheaply prepared as follows: Skim milk is heated in a copper boiler, if necessary by the introduction of steam, to 122° F. Then add for every 1000 quarts of milk, 3 quarts of crude hydrochloric acid diluted with 5 to 6 times the quantity of water. After coagulation, the whey is drained off, the curd spread out upon an inclined table and allowed to cool. The curd is then washed by pouring cold water over it through a rose, or stirring it up with water in a barrel, allowing to settle, and pouring off the supernatant water. The residue is subjected to moderate pressure. The caseine while still moist is comminuted in a curd-mill and packed in bags. In this state it must be worked at once, as otherwise it spoils readily and is attacked by worms. If it is to be kept for a longer time, it has to be dried. This is effected by spreading it out upon linen cloths and placing it in a drying chamber.
In this manner 8.5 per cent. of moist, or 3.5 per cent. of dry, caseine is obtained which is brought into commerce as technical caseine or lactarine. It being insoluble in water, 10 per cent. of an alkali—soda, borax, or ammonia—has to be added to effect solution. Water-soluble caseine is seldom found in commerce, the consumer preparing it, as a rule, himself.
A purer technical caseine is obtained according to John A. Just’s method as follows: Dissolve, stirring constantly, in 115 quarts of water heated to between 104° and 131° F., 17 to 26 ozs. of bicarbonate of soda and 176 lbs. of moist, or 118 lbs. of dry, caseine, and dry the solution upon a heated revolving metal cylinder. After each revolution of the cylinder, the dry material is scraped off with brushes and by being forced through a fine-meshed sieve yields soluble caseine powder.
Caseine cement which can be kept for a long time. Convert into powder, each by itself, 200 parts of caseine, 40 of burned lime, and 1 of camphor. Mix the powders intimately and keep the mixture in an air-tight bottle. For use, mix some of the powder with the requisite quantity of water and use the cement at once.
Cement for glass. Old dry cheese 100 parts, water 50, slaked lime 20.
Free the cheese from rind, and rub it with the water until a homogeneous mass drawing threads is formed. Then stir in quickly the lime powder, and use the cement at once. It unites not only glass to glass, but can also be used for cementing metal to glass.
Cement for metals. Elutriated quartz sand, 10 parts; caseine, 8; slaked lime, 10, and sufficient water to form a cream-like mass.