WARNING! CONTAINS ARSENIC. Please read the MSDS for cautionary statements. Realgar is a natural mineral of arsenic sulfide, usually described as orange red to orange yellow, and is designated as strong orange-yellow in Munsell notation 9.1YR 7.1/11.6. Realgar gets its name from the Arabic words for "powder of the mine" (rahj al ghar). We obtain realgar from deposits in the Hunan province of China, which has an orange color with a scintillating quality of the coarse ground pigment.
Origin and History Realgar is an historical pigment having been found as early as the fourteenth century B.C. as lumps of raw pigment in an Egyptian tomb.
Source It is usually found in mineral deposits of calcite along with orpiment and sometimes with other sulfide minerals, such as cinnabar. Excellent specimens of realgar were discovered in cavities of dolomite in Binnentale, Switzerland, and in calcite voids in Mercur, Utah, U.S. We obtain realgar from deposits in the Hunan province of China where it is found in large druses (cavities in a mineral filled with protruding crystals) of beautifully formed crystals. It exhibits an intense orange red color with a scintillating quality of the coarse ground pigment.
Permanence and Compatibility Early authorities usually described realgar as fading readily, or at least to some degree on exposure to light, and it appears to be less permanent than orpiment. It is said to be incompatible with lead- or copper-containing pigments. Several medieval painting guides do not recommend mixing sulfide pigments with lead white, minium (red lead oxide) or verdigris. It cannot be applied to wet plaster, and hence is not recommended in wet fresco painting techniques. Realgar is synthesized by heating orpiment to a temperature over 150°C or by sublimation of arsenic and sulfur. Although, the manmade mineral closely resembles the color and composition of realgar, it appears to be more susceptible to color change when exposed to light than natural realgar. It can lose its red hue and deteriorate to orange-yellow pararealgar when exposed to light.
Oil Absorption and Grinding No data has been published on the oil absorption properties of realgar. It is difficult to grind because of its micaceous structure. For this reason, it is often quite coarse. It has been suggested to add ground glass to the pigment to facilitate grinding and dispersion in linseed oil.
Toxicity The toxicity of arsenic sulfide pigments has been known for years. Extreme caution must be used when handling the dry pigment to avoid exposure to skin, ingesting it or inhaling the dust. Care must also be exercised while painting with it in any medium.
ASTM Lightfastness Rating
Color: Orange Red Color Index: Not Listed Chemical Name: Arsenic Sulfide Acrylic: Not rated Oil: Not rated Watercolor: Not rated Density: 3.5–3.6 g/cm3 Hardness: 1.5–2.0 Refractive Index: 2.538–2.704
Natural Pigments is a limited liability company based in Willits, California. We manufacture and distribute rare and hard-to-find materials for fine artists and decorators. We specialize in supplying artists' materials that were used in historical painting since pre-historic times up to and including the nineteenth century.
We constantly search for materials and products of the finest quality so that we can bring them direct to you from the source. To do so, we travel the world to find materials specifically for use by professional artists and decorators. We obtain minerals from mines in Afghanistan, Chile, Russia, Ukraine and Uzbekistan, to name a few places, processing these into natural pigments. We purchase resins, gums and plants from India, Kenya and Malaysia to make natural varnishes and painting mediums.
Our mission is to provide the largest variety of natural pigments, paints and other professional artists' supplies, enabling us to bring you a selection that makes shopping for rare and hard-to-find art materials easy. Our objective is to promote the education and use of these materials among artists by providing detailed information for their employment in encaustic, fresco, oil, watercolor and tempera painting.
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