THE PREPARATION OF PLASTIC MASSES FROM CASEIN. 97 



IMITATION IVORY. 



Milk curd, partly or wholly freed from its aqueous and 

 fatty constituents and broken up into small lumps, is kneaded 

 for about fifteen minutes in nearly boiling water. This treat- 

 ment causes the separation of fatty or granular impurities, 

 and leaves the casein in an almost perfectly pure state as a 

 tough, sticky mass. Care must, however, be taken not to 

 prolong the kneading beyond the proper stage, or the curd 

 will be too soft and pappy. The product may then be pressed 

 out into flat cakes or blocks of any desired shape. 



The casein prepared in this way can be mixed with pig- 

 ments or other materials, such as ivory dust, ground bone or 

 ground porcelain, according to the character of the article it 

 is intended to imitate. The prepared casein is stirred for 

 about ten minutes in hot water, which causes it to soften; 

 and it can then be incorporated with the necessary colouring 

 matter or other ingredients, and the resulting plastic mass 

 cast into moulds. 



The curd, freed from whey, may also be kneaded in its 

 own water of saturation, with a little more if necessary, at 

 a temperature approaching the boiling point. For this pur- 

 pose, the curd should be broken into small pieces, this treat- 

 ment facilitating the removal of fatty and other extraneous 

 matter. By this means, the curd can be worked at a lower 

 temperature and far more cheaply than by the first-named 

 method, and also furnishes a tougher quality of casein. The 

 colouring matters or other admixtures can be incorporated 

 as soon as the fat has been washed out and the mass has 

 been worked, thus saving a special mixing process. The 

 temperature to which the curd containing the water of satu- 

 ration is exposed, is about 120 to 175 F., according to the 

 character of the curd. It is then worked or kneaded for 



about fifteen minutes, with or without the addition of a little 



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