CAUTION!!! 
Do Not Expose These Peates to the Eight for a 
Longer Time Than Is Necessary. 
HE pigments used in the preparation of these Plates are the 
* most durable known, those which have been proven unstable 
having been, as far as possible, discarded. The latter include 
carmine and other cochineal lakes, colors of vegetable origin 
(as gamboge, violet carmine, indigo, etc.), and most of the aniline 
or coal tar dyes, though among the last are a considerable number 
which are really more permanent than several colors habitually 
used by artists. Certain colors in this work could not, however, 
possibly be reproduced except by the employment of pigments 
which are more or less sensitive to prolonged exposure to light, 
and hence this caution not to expose the plates unnecessarily. 
(See Church: “The Chemistry of Paints and Painting,” third edition, pages 
257-263.) 
