CASEIN PAINTS. 57 



For white, zinc white, white lead and barium sulphate 

 can only be used in small quantities and must be mixed with 

 the silicate just before use. 



Used for red, chrome red and red lead alter the silicate 

 less rapidly, but still too quickly to permit of their use to 

 more than a limited extent. 



On the other hand, an admixture of casein with silicate 

 paint retards the hardening of certain pigments, especially 

 white lead. The mixture is easily prepared by triturating 

 fresh curd with a little sodium silicate (density, 33 B.) to a 

 uniform mass and then stirring in the remainder of the 

 silicate. 



MILK PAINTS. 



Pigments are mixed with milk and water to workable 

 consistency, and then applied to a surface previously coated 

 with silicate paint. When the milk paint is dry, it is topped 

 with silicate paint by spraying. 



1. White. 2. Grey. 



3 parts milk. 3 parts milk. 



7 ,, water. 7 water. 



10 ,, zinc white. 10 ,, zinc white. 



part lampblack. 



3. Light Green. 4. Yellow. 



2 parts milk. 2 parts milk. 



5 ,. water. 5 water. 



10 zinc white. 10 ochre. 

 5 green earth. 



5. Brown. 6. Red-Brown. 



2 parts milk. 2 parts milk. 



5 water. 5 water. 



10 ,, umber. 10 ,, burnt sienna. 



7. Blue. 8. Black. 



2 parts milk. 2 parts milk. 



5 ,, water. 5 water. 



10 ,, ultramarine. 10 ,, ivory black. 



