Rublev Colours Pigment Luberon Raw Sienna - 4 oz

Natural sienna earth is a yellow pigment with a more or less brownish red tinge in the mass tone and a more or less yellowish undertone. It differs from the yellow ochre by having a much deeper colour, more than twice the tinting power, containing only two-fifths as much silica, only one-third as much alumina and from two and one-half to three times as much iron oxide hydroxide, and in addition to this from one to one and one-half per cent of manganese oxide, to the presence of which is due the difference in colour.

Iron oxide hydroxide is the principal color producing ingredient in sienna earths. The properties of the particular iron oxide hydroxide present in the earth determines its colour. The nature of the iron oxide found in the deposit, rather than its percentage, is critical to the resulting earth colour. Most rock contains some iron oxide. Those bearing the least amounts are limestone, white clay and colourless kaolin. Those containing the highest amounts are the rocks from which metallic iron is extracted.

Warning: The pigment is considered non-toxic, but care should always be exercised when handling the dry powder pigment so as not to inhale the dust.