CHAPTER VIII. 



THE PREPARATION OF PLASTIC MASSES FROM CASEIN. 



LIKE all substances possessing strong adhesive properties, 

 casein is specially adapted for the preparation of plastic 

 masses, which can be moulded, either in admixture with 

 organic substances like sawdust, wood meal, paper, etc., or 

 alone in the form of paste or a more or less dry powder, 

 and set hard when dry. Casein mixed with lime or other 

 alkaline material can be converted, by the addition of a little 

 water, into a plastic mass which, though very gradually, 

 dries in the air to a transparent mass as hard as bone, and 

 can be stained any colour. In this condition it can be turned 

 in the lathe or worked with any other cutting tool. When 

 plastic casein is mixed with other substances, such as organic 

 or finely powdered inorganic materials, the resulting masses 

 are endowed with the property of drying quickly, especially 

 under the influence of warmth. Care must, however, be 

 taken in the drying process, owing to the fact that all masses 

 containing much water shrink and easily crack while drying. 

 The adhesive properties of casein have already met with 

 extensive industrial application. Great success has attended, 

 for example, the attempts made to render celluloid uninflam- 

 mable by admixtures of casein ; and special mention will be 

 made later of the newest celluloid substitute, galalith. This 

 affords an instance of how modern ingenuity has enabled a 

 raw material, hitherto of but slight use technically, to become 



of great industrial utility. 



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