CAUTION!!!
 

Do Not Expose These Plates to the Light for a
Longer Time Than Is Necessary.

THE 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 Jje 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.

(^ee  chureli:  "The (.'ticniistry ol" Paint> and Piiiutint^," third edition, |i.ajics

2--.7---'r,.!.)