72 CASEIN. 



present, the whole being well mixed and left to stand until 

 the thicker, heavier constituents have settled down, where- 

 upon the supernatant liquid, which forms the medium, is 

 separated by decantation. This liquid has not the slightest 

 action on the most sensitive body colours, and its binding 

 power is unaffected by formaldehyde. It makes the colours 

 thoroughly workable and imparts great durability, so that 

 they can also be used for outdoor work, being able to stand 

 the weather. These colours are also suitable for use in calico 

 printing, since they are insoluble in water when once dry. 

 The sedimental matter can be ground and used as a cover paint. 



THE PREPARATION AND APPLICATION OF CASEIN PAINTS. 



To prepare artists' colours with casein, all that is neces- 

 sary is to take one of the media just described and mix it 

 with the appropriate pigments. The pigments most suitable 

 for white are : baryta, white lead, China clay, Paris white, 

 lithopone and zinc white ; for yellow : cadmium yellow, 

 chrome yellow, chrome, golden or pale ochre, Naples yellow, 

 " satinober," Schiitt yellow and Terra di Siena ; for red : col- 

 cothar, carmine, chrome red, fast red, Indian red, madder lake, 

 red lead, signal red, Terra pozzuoli, vermilion and vermilion- 

 ette ; for brown : asphaltum, Cassel brown, dark ochre, man- 

 ganese brown, Terra di Siena, umber, Vandyck brown ; for 

 blue : Berlin blue, Bremen blue, indigo, cobalt blue, blue-green 

 oxide and ultramarine ; for green : chrome green, chrome oxide 

 green, green earth, cobalt green, permanent green, Schwein- 

 furt green, and emerald green ; for black : ivory black, bone 

 black, lampblack and Paris black. 



To prepare small quantities, the binding media is mixed 

 with the dry pigments on a plate or sheet of glass, or else they 

 are ground with a muller or in a paint mill. The resulting 

 paint is thinned down to a workable condition with boiled 

 and recooled water at the time of use. 



