“Considering that it would be pointless to dwell at length on these colors, we will limit ourselves to pointing out those whose use is most widespread.
We will say, in substance, that among the coloring materials whose use we discourage, we include both those that rise too much in tone or that blacken, and those that fade or react with certain others by decomposing them. In a word, we reject any color that does not possess the qualities required to ensure complete stability in artistic painting.
We believe we must speak here, in a very particular way, about bitumen, which, as a pigment, is truly the worst material one could imagine. Bitumen acts on white, on madder lakes, and in general on all light toned colors laid over it, as tar would. That is to say, its oily component penetrates them and, over time, gives them a brownish tint. Bitumen never hardens. A relatively low heat softens it. It causes cracks that increase over the years, to the point of reaching several millimeters in width. We would wish for those of our readers who use this very pernicious substance to forget it entirely.
LIST OF COLORS UNSUITABLE FOR ARTISTIC PAINTING
Snow white.
Cochineal carmine.
Carmine lakes.
Calcined madder lakes.
Chrome yellows.
Note: Egyptian mummy has defects similar to those of bitumen.
Weld lake.
Stil de grain (buckthorn lake).
Indian yellow.
Zinc yellow.
Antimony yellow.
Raw sienna.
Green earth or Verona green.
Green ochres.
Paris green.
Scheele’s green.
Schweinfurt green.
Green cinnabars.
Green lakes.
Malachite green.
Cobalt green.
Mineral blue.
Prussian blue.
Violet lakes.
Umber.
Bitumen.
Egyptian mummy.
Ivory brown.
Many other colors could be added to this list, but since they are rarely prepared in oil, we do not think it necessary to mention them.”
