CASEIN PAINTS. 59 



holds well on, metal, and becomes insoluble in water on 

 drying. 



CALSOMINE WASH. 



This preparation consists of a mineral base in combination 

 with a binding medium having the property of solubility in 

 water and oxidising to a perfectly insoluble product when 

 exposed to the air in the form of a coat of paint. This paint 

 is therefore waterproof, and possesses the properties of oil 

 paint in this respect and in power of standing the influence 

 of the weather. The pigment is a white or coloured powder 

 consisting fundamentally of magnesium silicate or talc, and 

 is added to the binding medium in the proportion of 90 parts 

 to 10. It is also practicable to use 20 parts of lime, 70 of 

 chalk and 10 of binding medium ; and these proportions may 

 be modified in turn. The binding medium is compounded 

 of casein and lime, the former being obtained, as a dry white 

 powder, by treating milk with an acid at 100 F. Sixty 

 parts of this powder are mixed with 20 parts of dry slaked 

 lime, whereupon the casein becomes soluble in water, though 

 this property disappears on oxidation. Any convenient body 

 colour may be incorporated with the mixture, and when the 

 whole is thinned with water it furnishes an easy working 

 and waterproof paint. 



QUICK-DRYING CASEIN PAINT. 



When mixed with such volatile substances as turps, 

 petroleum, benzol, etc., dissociated casein acquires the pro- 

 perty of drying very quickly. Hence, by preparing a solution 

 of casein along with oil or balsam, and thinning it down with 

 petroleum, a product is obtained which is highly elastic as 

 well as quick drying. 



A mixture of 8 parts of this medium, with about 10 of 

 zinc white, lithopone, etc., forms a very useful light paint 

 for outdoor or indoor use on wookwork or metal. It is worth 



