Many Colours Are Apt To Change From The Action Of White Lead And Other
:
ON COLOURS AND PIGMENTS GENERALLY.
lead pigments, &c., principally those which are altered by light and
air.
Many, too, cannot safely come into contact with iron, or ferruginous
pigments; especially the yellows of arsenic, the lakes of cochineal, and
the blues and greens of copper. With these an iron palette knife is best
avoided, one of ivory or horn being used instead. The latter, indeed, is
preferable in all cases, several pigments being slightly affected by
iron, cadmium yellow among the number.