Spirit varnishes are coloured with coal-tar dyes soluble in spirit, and usually known as " spirit soluble " dyes. As a rule, very little dye is required. Perhaps the best way to apply it is to make a concentrated solution of the dye in spirit, and add this drop by drop to the varnish till it is sufficiently coloured. The names of some of the dyes are magenta, methyl violet, methylene blue, brilliant green, Bismarck brown, aurantia, eosin, nigrosin, etc.