This color contains the following pigments:
hydrated iron oxide
α-FeO3+(OH) or Fe2O3
Raw Sienna is a moderately dull deep earth yellow with medium tinting strength and excellent transparency. It is one of the basic permanent artists' pigments and is made from a form of limonite clay whose yellow-brown color results from ferric oxides. Raw Sienna is preferable to Yellow Ochre for creating flesh tones, due to its higher subtlety of color when mixed with white. It creates a bright Ochre when mixed with Cadmium Yellow and creates greens and grays when mixed with Ultramarine. Raw Sienna dries quickly.
Raw Sienna has good permanence.
Raw Sienna has no significant hazards.
Raw Sienna has been used as a pigment since prehistoric times, although its current name came about during the Renaissance. It comes from the city of Siena, in Italy, and is short for terra di Siena, meaning earth of Siena. Sienna was famous for the mining and production of earth pigments from the Renaissance until World War II. Due to the depletion of clay deposits in Tuscany, Italian siennas now come from other areas, including Sicily and Sardinia.
iron(III)-oxide, partly hydrated
Brown Ochre provides artists with earthtones from cream to brown and is a dull, dark variety of Yellow Ochre. Its transparency varies widely from opaque shades to more transparent ones, which are valued for their use as glazes. It has good hiding power, produces a quick drying paint, and can be safely mixed with other pigments. The highest quality Brown Ochre comes from Cyprus, where it is yellow in its raw form and is roasted to get the deeper brown-red varieties that result when water is removed. (See Yellow Ochre, PY42/43.)
Brown Ochre has excellent permanence.
Brown Ochre is non-toxic.
Ochre comes from the Greek word ochros, meaning pale yellow. It has been used since prehistoric times, and evidence of its use has been found in some of the earliest known cave paintings in Lascaux, France. It has also been called Goethite, after the German philosopher and mineralogist Johann Wolfgang von Goethe (1749-1832).