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Alumina Toxicology | Ammonia and Latex Toxicity | Antimony Oxide | Are colored porcelains hazardous? | Arsenic Oxide | Asbestos: A Difficult-to-Repace Material | Ball Clay | BARIUM and COMPOUNDS / Toxicology | Barium Carbonate | Bentonite Toxicity | Beryllium Monoxide Toxicology | Bismuth Trioxide Toxicology | Boron Compounds and Their Toxicity | Brown Stain | Cadmium Toxicity | Calcium Carbonate Toxicology | Carbon Monoxide Toxicity | Cesium Toxicology | Chromium Compounds Toxicology | | Cobalt Oxide and Carbonate | Cobalt Toxicology | Copper Compounds Toxicology | Copper Oxide and Carbonate | Cristobalite Toxicity | Cryolite and Ceramics | Dealing With Dust in Ceramics | Diatomaceous Earth Toxicology | Dioxins in Clays | Epsom Salts | Eye Injuries Due to Radiation | Feldspar | Fighting Micro-Organisms in Ceramics | Fluorine Gas | Gallium Oxide Toxicology | Hafnium Oxide Toxicty | Hydrofluoric Acid Toxicity | Iron oxide and Hematite | Lead Chromate | Lead in Ceramic Glazes | Lead Toxicology | Lithium Carbonate Toxicity | Lithium Toxicology | Man-Made Vitreous Fibers (MMVF) Toxicology | Man-Made Vitreous Fibers Safety Update | Manganese and Parkinsons by Jane Watkins | Manganese in Clay Bodies | Manganese Inorganic Compounds Toxicology | Manganese Toxicity by Elke Blodgett | Manganese: Creativity and Illness by Dierdre O'Reilly | Molybdenum Compounds Toxicology | Nickel Compounds Toxicity | Niobium Oxide Toxicity | Occupational Dermatoses | Overview of Material Safety by Gavin Stairs | Paraffin Toxicology | Perlite Toxicity | Plant Ash Toxicity | Potassium Carbonate Toxicity | Pregnancy and Ceramics | Propane Toxicology | Quartz Toxicity | Quartz Toxicity on Clayart | Rare Earth Compounds Toxicity | Rubidium and Cesium Toxicology | Rutile Toxicology | Silicosis and Screening | Silver Compounds Toxicology | Sodium Azide Toxicology | Sodium Carbonate Toxicology | Sodium Silicate Powder Toxicology | Stannous Chloride Toxicity | Strontium Carbonate Toxicity Note | Sulfur Dioxide Toxicity | Talc Hazards Overview | Talc Toxicology | Thallium Oxide Toxicology | The Use of Barium in Clay Bodies | Thorium Dioxide Toxicity | Tin Inorganic Compounds | Titanium Dioxide Toxicology | Toxicological Assessment of Zeolites | Tungsten Compounds Toxicology | Understanding Acronyms on MSDS's | Uranium and Ceramics | Vanadium and Compounds Toxicology | Vermiculite | Zinc Compounds Toxicology | Zirconium Compounds Toxicity | Zirconium Encapsulated Stains Toxicity

Clay Toxicity

Kaolin is the purest clay that nature offers, one TLV (threshold limit value) quoted for it is 2.0 milligrams per cubic meter of air breathed (primarily because of the potential of associated quartz). By comparison, iron oxide is considered a safe-to-use material at 5.0, tin oxide is 2.0, barium carbonate is 0.5, quartz is 0.1-0.05.

Some books cite the presence of some free silica in kaolin as a silicosis hazard; however, other sources and regulatory bodies recognize no known hazards and consider it a nuisance dust (quartz often less than 1%). Ball clays, on the other hand, can have a much higher quartz content. That being said, the grains are often round rather than angular.

Like many clays, data sheets often caution against slipping on a slippery aqueous suspension if it gets spilled on the floor!

ALLERGIES: Clays are composed of tiny particles of inert minerals (thus insoluble). Some clays are relatively homogeneous (all the particles are the same) and some are composites (containing particles of many minerals). Molds, mildews, and other organisms can make their home in clay, along with their byproducts, and thus cause reactions. Sedimentary clays can contain calcium and magnesium sulfates, these are at least partially soluble and there is thus a possibility of allergy (however sulfates are common additives to many household products are not considered hazardous).

By Tony Hansen
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Related Information

Mold growing in a clay having added xantham gum

This slug is about 6 months old. It contains 0.75% gum. The gum destroys the workability of the clay so it is not useful in this application anyway.

Something gross is growing in this jar of prepared glaze

Even though most prepared glazes contain some sort of biocide, apparently this can still happen!

Mold (actually sprouting leaves) has grown on pugged clay

After 10 months of storage (where there is sunlight).


Materials Kaolin
The purest of all clays in nature. Kaolins are used in porcelains and stonewares to impart whiteness, in glazes to supply Al2O3 and to suspend slurries.
Glossary Micro Organisms
Ceramic glazes and clay bodies can host micro organisms. They can be just a nuisance, a source of worry or can render a product useless. What should you do?

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