Kaolin
Description
A type of [[primary clay] formed by the weathering of aluminum silicates, such as feldspars and Nepheline. When pure, kaolin is a soft, white, absorbent powder composed primarily of the mineral Kaolinite, a hydrated aluminum silicate. Impurities, such as iron oxide, silica, and other minerals, can produce yellow, red, blue, gray, or brownish color clays. Kaolin occurs at many locations around the world (France, England, Germany, China, United States, etc.). Kaolin is used to produce fine quality Porcelain and china. It is also used as a base for lake colors and as a filler in paints, pastels, papers, rubbers, cements, and epoxies. Kaolin (as brick dust) has been used as an Abrasive for polishing Gold and other metals. It is also a useful Absorbent for oils and greases and has been used commercially for cleaning fabrics, furs, and carpets.
Synonyms and Related Terms
kaolinite; China clay; Devonshire clay; Pigment White 19; CI 77005; Kaolinit (Deut.); Satinkreide (Deut.); caolín (Esp.); kaoliini (Fin.); kaolin (Fr.); blanc de Chine (Fr.); kaolinis (Gr.); caolino (It.); terra bianca (It.); bolo bianco (It.); creta Eretria (old Roman); bolus alba (old Roman); kaolien (Ned.); caulino (Port.); satinkrita (Sven.); dkar po (Tibetan); bolus alba; porcelain clay; white bole; argilla; paper clay; brick dust; fuller's earth; white bolus; white heart; pipe clay; pipeclay;
Other Properties
Insoluble in water, cold acids or alkalis
Microscopically particles are translucent and colorless with moderate relief. Under crossed polars, particles have low birefringence.
Kaolin fluoresces a pale white.
| Composition | Al2Si2O5(OH4) |
|---|---|
| CAS | 1332-58-7 |
| Mohs Hardness | 2.0 - 2.5 |
| Density | 2.6-2.63 |
| Refractive Index | 1.558; 1.565; 1.564 |
Hazards and Safety
Noncombustible
Mallinckrodt Baker: MSDS
Additional Information
WebMinerals: Kaolinite
Comparisons
Properties of Common Abrasives
Characteristics of Common White Pigments
Sources Checked for Data in Record
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- R. J. Gettens, G.L. Stout, Painting Materials, A Short Encyclopaedia, Dover Publications, New York, 1966
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- Robert Fournier, Illustrated Dictionary of Practical Pottery, Chilton Book Company, Radnor, PA, 1992
- Encyclopedia Britannica, http://www.britannica.com Comment: "Kaolin." Encyclopædia Britannica. 2 Sept. 2004 .
- Wikipedia, the free encyclopedia, at http://www.wikipedia.com Comment: http://en.wikipedia.org/wiki/Kaolin (Accessed Feb. 10, 2006)
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- Art and Architecture Thesaurus Online, http://www.getty.edu/research/tools/vocabulary/aat/, J. Paul Getty Trust, Los Angeles, 2000