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.
Alizarin Crimson, the traditional cool counterpart to Cadmium Red, is a clear ruby-red with a maroon masstone and a bluish undertone. It is the artist's principal deep red pigment, is transparent, and has good tinting strength. It creates bright rosy pinks when mixed with white, a range of purples and violets when mixed with strong blues, can be slow drying when used with oils, and is compatible with all other pigments. Permanent Alizarin Crimson mixes well with Ultramarine in acrylic and watercolor form. Permanent Rose and Quinacridone Rose are possible alternatives on a watercolor palette. Alizarin Crimson is a popular glazing color.
Alizarin Crimson is considered fugitive or marginally lightfast, and the appropriateness of its use in the modern artist palette is a subject of debate. There are many concerns regarding its permanence, particularly when mixed with ochre, sienna, and umber, or when used thinly. It is the least permanent red commonly used by today’s artists. Modern synthetic preparations of Alizarin Crimson have better permanence and lightfastness that the original natural pigment, which was extracted from the madder plant. Quinacridone pigments have been used to create a modern hue that closely matches the original hue, but many artists object that the transparency and handling characteristics are not the same as for the original.
Alizarin Crimson can be slightly toxic if it comes into contact with skin and may cause some allergies. There is no significant acute toxicity.
The word alizarin comes from the Arabic word al-usara, meaning juice. The base ingredient of this pigment is the Madder plant (Rubia Tinctorum). It was used for dyes and inks among craftsmen in Ancient Persia, India, and Egypt as early as 1500 BC In 1804, George Field, an English dye maker, developed Madder Lake by binding madder to alum, a white powder. The German chemists Carl Grabe and Carl Liebermann produced the first synthetic variety of this pigment, most commonly known as Alizarin Crimson, in 1868. They used anthracene, which greatly improved the lightfastness. The Colour Index International designation PR83:1 has been used to identify this synthetic laked pigment.