Alizarin Crimson Pigment
Alizarin Crimson is a red color that is biased slightly more towards purple than towards orange on the color wheel. It is named after the organic dye alizarin, found in the madder plant, and the related synthetic lake pigment alizarin crimson (Colour Index PR83).
The roots of the plant Rubia tinctorum supply the coloring substances that are converted to madder lakes, the principle coloring substance which is alizarin. Alizarin crimson is a red color that is biased slightly more towards purple than towards orange on the color wheel. It is named after the organic dye alizarin, found in the madder plant, and the synthetic lake pigment alizarin crimson (Colour Index PR83).
|Common Names (Dye):
|alizarin, alizarine, purpurin, Rubia tinctorum
|Common Names (Synthetic Pigment):
|1,2-Dihydroxy-9,10-anthracenedione, 1,2-Dihydroxyanthraquinone, Turkey red, Mordant red 11, Alizarin B, Alizarin red
|Common Names (Natural Pigment):
|English: madder lake
French: laque de garance
Italian: lacca di robbia
Portuguese: laca de ruiva
Spanish: laca de rubia
Origin and History
Madder has been cultivated as a dyestuff since antiquity in central Asia and Egypt, where it was grown as early as 1500 B.C. Cloth dyed with madder root pigment was found in the tomb of the Pharaoh Tutankhamun and in the ruins of Pompeii and ancient Corinth. In the middle ages, Charlemagne encouraged madder cultivation. It grew well in the sandy soils of the Netherlands and became an important part of the local economy.
Thompson thinks that the madder lakes were less employed in medieval painting then were the brazil lakes. He says that pure madders, as they are known now, came into use in the 17th and 18th centuries and that they were not important in the Middle Ages [The Materials of Medieval Painting, pp. 123-124].
By 1804, the English dye-maker, George Field, had developed a technique to lake madder by treating it with alum. This turned the water-soluble madder extract into a solid, insoluble pigment. This resulting madder lake had a longer-lasting color, and could be used more versatilely, for example by blending it into a paint. Over the following years, it was found that other metal salts, including those containing iron, tin, and chromium, could be use in place of alum to give madder-based pigments of various other colors.
In 1826, the French chemist Pierre-Jean Robiquet found there were two colorants in madder root, alizarin and the more rapidly fading purpurin. The alizarin component became the first natural dye to be synthetically duplicated in 1868 when the German chemists Karl Graebe and Karl Lieberman, working for BASF, found a way to produce it from anthracene. About the same time, the English dye chemist William Perkin independently discovered the same synthesis, although the BASF group filed their patent before Perkin by only one day. The synthetic alizarin could be produced at less than half the cost of the natural product, and the market for madder collapsed virtually overnight. Alizarin itself has been in turn largely replaced today by the more light-resistant quinacridone pigments developed at DuPont in 1958.
Alizarin crimson is a synthetic lake pigment based on the dye alizarin precipitated onto aluminum.
Preparation of Lake Pigment
Pigments and dyes are not identical, although there are cases in which the same coloring matter which yields a dye or stain may give rise to a pigment. A pigment is, in fact, a substance which is insoluble in the vehicle with which it is mixed to make a paint, while a dye is soluble. A lake pigment is a natural organic pigment prepared when a dye has been precipitated on a powdered, colorless, inorganic substrate. The term derives from the Latin word lacca, used in the Middle Ages to denote both lake pigments and the Lac dye. Because of its transparency, aluminum hydroxide is the most commonly used substrate or carrier. Barites, such as barium sulfate, provide an opaque lake pigment. Other compounds used as carriers are: chalk, clay, gypsum, tin oxide, zinc oxide, white earth, and green earth. Often a mordant, such as tannic acid, lactic acid, or sodium phosphate, is used to fix the dye to the substrate. Madder lake and rose madder for artists' pigments are prepared from madder extract by adding alum and precipitating with an alkali.
Permanence and Compatibility
It is a beautiful transparent red, but impermanent. Alizarin crimson has been rated for lightfastness y the ASTM Alizarin is known to fade upon exposure to strong light, but the darker tones and/or applications without white are more permanent. In fresco, lime destroys alizarin completely. Alizarin requires about 50% binder, dries poorly and should therefore be first mixed with alkali-refined linseed oil and ground finely.
Oil Absorption and Grinding
Alizarin has a high oil absorption rate of 100 to 120 grams of linseed oil for every 100 grams of pigment. Due to the very fine particle size of this pigment, it is difficult to grind and requires many grinds to separate and disperse the pigment in oil and water.
The pigment alizarin crimson is considered to be non-toxic.
|Pigment Red 83 (5800)
|ASTM Lightfastness Rating
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