LUMINOUS SHOWERS. 159 



varnish, 10 parts precipitated barium sulphate, 8 parts auri 

 pigment, and 34 parts luminous calcium sulphide. 



Luminous colors for artists' use are prepared by using East 

 India poppy oil in the same quantity, instead of the var- 

 nish, and taking particular pains to grind the materials as 

 fine as possible. 



For luminous oil-color paints, equal quantities of pure lin- 

 seed oil are used in place of the varnish. The linseed oil 

 must be cold-pressed, and thickened by heat. All the 

 above luminous paints can be used in the manufacture of 

 colored papers, etc., if the varnish is altogether omitted, and 

 the dry mixtures are ground to a paste with water. 



The luminous paints can also be used as wax colors for 

 painting on glass and similar objects, by adding, instead of 

 the varnish, ten per cent more of Japanese wax, and one- 

 fourth the quantity of the latter of olive oil. The wax 

 colors prepared in this way may also be used for painting 

 upon porcelain, and are then carefully burned without access 

 of air. Paintings of this kind can also be treated with 

 water-glass. 



