76 CASEIN. 



with colour that has merely been mixed with water without 

 any casein medium. At the same time the under layer is 

 kept well moistened with water throughout the entire process. 

 If the dried paint is to be topped, the surface must be sprayed 

 with the casein medium diluted 8- to 10 -fold with water, and 

 the paint applied as above. 



In painting pictures on outside work, the casein medium 

 prepared with the assistance of oil, balsams and fats or wax 

 and resin is used. For the first coating on absorbent sur- 

 faces this is mixed with ordinary amber varnish which im- 

 proves the drying and furnishes a handsome gloss. 



If, on the other hand, drying is to be retarded in order 

 to be able to work the colours together longer, then a little 

 oil is added to the medium or the same is mixed with oil 

 paint. Should the surface nevertheless get too dry, the 

 true shade of the colours may be revealed by moistening 

 with turps. 



To coat the pictures with glossy varnish, as though they 

 were oil paintings, a coating of glossy varnish or some other 

 thick varnish must be brushed in, and when this is dry it 

 should be covered by a second coat of varnish. 



The varnish may be replaced by a coating of wax solu- 

 tion, the dried layer being heated to melting point in order 

 to increase the durability and powers of resistance. The 

 same purpose is also served by the paint soap and impreg- 

 nating varnish, as well as the formaldehyde solutions already 

 mentioned, though these can only be used on casein paintings 

 that are free from fatty matters. 



A fixative of this kind can be prepared by dissolving 

 casein in methyl alcohol, or by treating an aqueous solution 

 of casein and borax with absolute methyl alcohol free from 

 acetone, the solution being left to stand for a long time and 

 separated from the sediment. 



According to Chialiva and Dupot, in their patent specifica- 



