CAUTION!!! 



Do. Not Expose Thkse Plates to the IvIGht 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 "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.) 



