<P> The color of oil paint derives from small particles of colored pigments mixed with the carrier . Some of the earliest known pigments are charcoal (black), iron oxide (rust red), and gypsum (white). </P> <P> Common pigment types include mineral salts such as white oxides: zinc, titanium, and the red to yellow cadmium pigments . Another class consists of earth types, e.g. sienna or umber . Still another group of pigments comes from living organisms, such as madder root . </P> <P> Synthetic pigments are also now available . Natural pigments have the advantage of being well understood through centuries of use, but synthetics have greatly increased the spectrum of available colors, and many are tested well for their lightfastness . </P> <P> Many of the historical pigments were dangerous, and many pigments still in popular use today are highly toxic . Some of the most poisonous pigments, such as Paris green (copper (II) acetoarsenite) and orpiment (arsenic sulfide), have fallen from use . </P>

Who developed the technology of painting with oils