Dyes and Pigments for Maxwell Disks. 27 
for overwashes of the light blue merely sink through 
and darken the color without improving the hue. A 
moderately saturated solution of the light blue should 
be applied first, and when this is dry covered with one 
or more rather thin washes of the permanent blue or 
new blue). 
Hues between blue and violet. —Winsor and Newton’s 
permane?it blue and some of the more violet-hued arti¬ 
ficial ultramarines, the hues nearer violet washed with 
crystal violet or gentia?i violet . 
Violet. —Crystal violet. 
Hues between violet and red .— Methyl violet ib. washed 
with rhodamin b.; for hues nearer red, rhodamin b. with 
Devoe’s geranium red (dry) or crocein scarlet b. 
While more or less similar in hue to rhodamin b., 
several other aniline dyes, as acid fuchsin, rubin s.> 
rosein , magenta , etc., do not combine satisfactory with 
the violets, the mixture soon becoming dark or dull and 
none of them are quite as pure a purple or red-violet. 
It is most important to remember that disks thus 
colored must be carefully protected from light when not 
in actual use and never exposed to direct sunlight. The 
artificial ultramarines are, of course, permanent, and so, 
practically, are crocein scarlet, gold orange, orange g., 
and auramin—that is to say, are not materially affected 
by the action of light except after very prolonged expo¬ 
sure, though the last named undergoes a change of hue; 
but the green and violet aniline dyes are all very evanes¬ 
cent, rapidly fading and eventually disappearing; light 
blue and rhodamin, while sensitive to light, are far.less 
so than the greens and violets. 
