There are colours which purify by fire, such as the yellow oaker, brown red, ultramarine, and umber; all others blacken thereby: But if you burn the above-nam’d colours with a strong fire they change; for the brown red turns yellow, the yellow oaker turns red, the umber reddens also, and white lead becomes of a lemon volour, and is call’d masticot. Observe, yhat the yellow oaker burnt becomes softer and kinder by far than before, and more so than the pure brown red: and reciprocally the brown red being burnt becomes more soft and agreeable than the pure yellow oaker; they are both very good