RE: archivalness of gum
<< I think gamboge, lakes, etc. are also names of tones, not pigments, tho some pigments could be so named, I suppose... >> I believe many of them are originally pigments of dyes. Like gamboge is a plant. I have use true gamboge in painting. It is in a form of a stick (they take the liquid (sap?) from the plant and put in in a thin bamboo trunk and after it dries, they break the trunk to get the gamboge out). You "grind" it like you grind an ink stone, but it is not actually grinding, it is more like dissolving. Gamboge is not permanent, so today it is replaced by more permanent synthetic version, so gamboge becomes a tone name. Lakes are all plant dyes and so are very fugitive too. Today's lake are indeed hue/tone names made from synthetic mixes. Same with indigo which originally was made from indigo plant. It has a beautiful purple tone, but it is also fugitive. Today's indigo is a mixture of prussian blue and quinacridone red. Those who are used to true indigo sometimes complain that the synthetic indigo is too colorful (the true indigo is more muted), but this can be fixed easily by adding just a touch of black; so today's indigo is also a hue name. Dave
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