Fuller's earth is any clay material that has the capability to decolorize oil or other liquids without chemical treatment. Fuller's earth typically consists of palygorskite (attapulgite) or bentonite.
Modern uses of fuller's earth include absorbents for oil, grease, and animal waste (cat litter) and as a carrier for pesticides and fertilizers. Minor uses include filtering, clarifying, and decolorizing; and as filler in paint, plaster, adhesives, and pharmaceuticals.
The name reflects the historic use of the material for cleaning or "fulling" wool by textile workers called "fullers". In past centuries, fullers kneaded fuller's earth and water into woollen cloth to absorb lanolin, oils, and other greasy impurities as part of the cloth finishing process.
Fuller's earth is also sometimes called "bleaching clay", probably because fulling whitened the cloth.
Occurrence and composition
Fuller's earth consists primarily of hydrous aluminum silicates (clay minerals) of varying composition. Common components are montmorillonite, kaolinite and attapulgite. Small amounts of other minerals may be present in fuller's earth deposits, including calcite, dolomite, and quartz. In some localities fuller's earth refers to calcium bentonite, which is altered volcanic ash composed mostly of montmorillonite.
In 2005, the United States was the largest producer of fuller's earth with an almost 70% world share followed at a distance by Japan and Mexico. In the United States fuller's earth is typically derived from deposits of volcanic ash of Cretaceous age and younger (glacial clays do not form fuller's earth). Fuller's earth deposits have been mined in 24 states.
In the United Kingdom, fuller's earth occurs mainly in England. It has been mined in the Lower Greensand Group and the Vale of White Horse, Oxfordshire. The Combe Hay Mine was a fuller's earth mine operating to the south of Bath, Somerset until 1979. Other sites south of Bath included Frome, Lonsdale, Englishcombe, Tucking Mill and Duncorn Hill. Although these sites had been used since Roman times, William Smith developed new methods for the identification of deposits of fuller's earth to the south of Bath. Other English sources include a mine near Redhill, Surrey (worked until 2000), and Woburn, Bedfordshire, where production ceased in 2004.
Hills, cliffs, and slopes that contain fuller's earth can be unstable, since this material can be thixotropic when saturated by heavy rainfall.
In addition to its original use in the fulling of raw fibers, fuller's earth is now utilized in a number of industries. Most important applications make use of the minerals' natural absorbent properties in products sold as absorbents or filters.
- Decontamination: Fuller's earth is used by military and civil emergency service personnel to decontaminate the clothing and equipment of servicemen and CBRN (Chemical Biological Radiological Nuclear) responders who have been contaminated with chemical agents.
- Cleaning agent: In the Indian subcontinent, it has been used for centuries to clean marble. As a good absorbent, it removes dust, dirt, impurities and stains from the surface and replenishes the shine of the marble. It has been used numerous times to clean the Taj Mahal, India with positive results.
- Litter box: Since the late 1940s, fuller's earth has been used in commercial cat litter.
- Film industry: Fuller's earth has been used extensively for many years in motion pictures for a variety of applications. In the area of special effects, it is used in pyrotechnics explosions and dust clouds, because it spreads farther and higher than most natural soils, resulting in a blast that looks larger. It is also safer than naturally occurring soil, should the blast spray hit actors. The material was used in the tornado sequence in The Wizard of Oz as the artificial twister plowed its way toward the farmhouse. Fuller's earth is also widely used by the make-up, props, wardrobe, and set dresser departments, because it is considered a "clean" dirt, safer to use around people, and it cleans up easily. However, health concerns in this regard have been debated. Fuller's earth is available in small quantities by make-up suppliers for use in making the face and body appear dirty. It is used by props technicians to make furniture look dusty. Wardrobe dressers use a small, loose-mesh cloth bag filled with fuller's earth to apply it to clothing to make it appear dusty. Set dressers use fuller's earth to change paved streets into dirt roads, to create dust trailing from a moving vehicle over a dirt road, or to indicate a vehicle trail over untraveled ground.
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