Pigment Information:
Cerussite (Natural Lead White)
Alternate Names: lead white, white lead, flake white, and Cremnintz white are names given to synthetic lead carbonate pigment. Latin: cerussa Color: White Colour Index: Pigment White 1 ASTM Lightfastness: Oil: I Acrylic: I Watercolor: Not tested Density: 6.5+ Hardness: 3-3.5 Refractive Index: 2.07 Chemical Formula: PbCO3
Cerussite is natural lead carbonate, and is close in composition to lead white or flake white. The name of the mineral comes from Latin cerussa for whiting. The mineral is found in the oxidation zone of lead deposits usually associated with galena. Cerussite is sometimes found in association with another lead mineral, anglesite, a yellow colored, lead sulfate. Cerussite is a typical secondary mineral. It comes into being by the natural weathering of galenite. Sulfuric acid released in the process dissolves the surrounding carbonate rock, thereby releasing carbon dioxide to form cerussite. At first anglesite (PbSO4) is formed but this mineral is soon transformed into cerussite when it comes into contact with carbonic acid in water. Lamellar or acicular crystals of white or gray color are formed. They have a very high luster due mostly to the lead content. Just as leaded crystal glass sparkles more brilliantly because of its lead content, so too does cerussite. Lead raises the refraction index of cerussite to just over 2.07. Because of its high refractive index, the hiding power of lead white, even in oil, is high. Lead is also responsible for its increased density or specific gravity. Cerussite has one of the highest densities for a mineral. It is over 6.5 times as dense as water. Most minerals average only around three times the density of water.
History of Use: Although the natural mineral cerussite has rarely been noted in paintings, its synthetic counterpart, lead white, is considered to be the most important white pigment in paintings since the time of ancient Greece.
Origin: We get our cerussite from a source in Kazakhstan.
Permanence and Compatibility: Despite cerussite being a carbonate, and hence sensitive to acids, it has an excellent record for permanence. It is unaffected by light. When applied in watercolor technique, however, traces of hydrogen sulfide in the air may cause it to turn black. Although lead white is theoretically incompatible with sulfide pigments, and should form black lead sulfide in contact with them, no examples are readily known. There might be some doubt, however, about mixing orpiment and realgar with lead white, although some identified cases show no discoloration.
Oil Absorption and Grinding: A special feature of lead white is its low oil-absorption rate. According to some it requires only 9 to 13 milliliters of oil to make a workable paste with 100 grams of lead white. It quickens the drying time of oil paints. It can be used with aqueous media such as egg tempera, gum Arabic (watercolor), and with animal glue. It can also be used in encaustic (wax) technique, but does not appear to perform well in true fresco technique.
Toxicity: Cerussite is toxic and care should be used in handling the dry powder pigment so as not to inhale its dust, as well as the pigment dispersed in medium.
 Read cautions about handling pigments
|
New Products
