CASEIN PAINTS. 63 



tion of casein. The coating is waterproof and washable, 

 whilst still leaving the paper sufficiently absorbent to allow 

 the cards to be printed in the usual way. 



The best mixture for this purpose consists of 80 parts of 

 satin white, 16 of casein, 2 to 4 of caustic soda or ammonia 

 and 25 or more of water. The inventor of the preparation 

 believes that the satin white combines with the dissolved 

 casein in such a manner as to render the latter insoluble 

 when the coating has been applied and allowed to dry for 

 some time. 



This coating is said to be particularly useful in imparting 

 to playing cards the desired enamel-like appearance, and to 

 be capable of taking the most delicate multiple colour print- 

 ing. The satin white may be partly replaced by blanc fixe. 



CASEIN COLOUR LAKE. 



The use of casein as a precipitant is advisable in making 

 colour lakes, kaolin being employed as the substratum. For 

 instance, Dreher recommends grinding to paste 30 parts of 

 finely ground kaolin and 20 of lukewarm water, followed by 

 repeating the operation with an addition of 80 parts of dis- 

 solved casein (10 parts of casein, 20 of water and 1 to 2 of 

 ammonia). One hundred parts of dye solution (0'5 per cent, 

 strength) are next added and well mixed, the whole being 

 then treated with 2 parts of a 1 per cent, solution of tin tetra- 

 chloride, added drop by drop. After being washed and 

 pressed, the precipitate is dried at 60 C., or at 80 to 100 

 C. if the dye will stand that temperature. Both acid and 

 basic aniline dyes can be precipitated on any substratum by 

 this method. The resulting lakes are very bright in colour 

 and are very fast to water. Tin tetrachloride may be re- 

 placed by other salts having an acid reaction, such as alu- 

 minium chloride, tin acetate, etc., but the acetate must be 

 freed from any excess of acetic acid, since this exerts a 



