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Poisons in Pottery


There are poisons in pottery that potters need to be aware of. In this time of readily available information and safety equipment, it is only common sense to pay attention to what can harm yourself or those around you.

Take the time to learn how to protect yourself, your studio visitors, and those who use your wares from the poisonous substances inherent in producing pottery. With simple precautions, you can avoid heartache and trouble.

Remember: always use respirators any time you are mixing dry materials. Also use rubber or latex gloves when mixing and using glazes and stains.


Barium carbonate, which is used by potters, is a dangerous form of barium. Because it becomes soluble in acidic environments, any barium ingested will produce a soluble chloride in the stomach. Barium can also enter the body through inhalation or through broken skin.

Initially, barium poisoning can lead to severe abdominal pain, nausea, diarrhea, and vomiting. Barium poisoning’s predominant effects are to the muscles, in particular the heart. There may be muscle weakness, and severe muscle cramps. More seriously, there can be difficult breathing, high blood pressure, tachycardia, and possibly death.

Glazes which contain barium are not recommended for food ware, as it may leach into foods or liquids.


Borax (boric oxide) is a powerful flux and is used in glazes and occasionally in clay bodies, often in the form of a frit. Chronic exposure to borax can cause asthma, diarrhea and skin conditions.


Cadmium is used as a pigment in glazes. Its point of entry into the body is through inhalation.

Cadmium can cause a number of problems, including lesions in the lung and nasal tissues, respiratory diseases, osteoporosis, cancer and other problems. There is also evidence that cadmium poisoning can damage genetic materials, such as chromosomes.

Do not use on any ware that may be used for food or consumable liquids.


Chrome is used by potters in the forms of green chromium oxide, iron chromite, and potassium dichromate. These are used in slips and glazes as colorants. It will enter the body through inhalation, ingestion, and broken skin.

Chrome poisoning may include problems with the skin, gastrointestinal system, kidneys, and lungs. Iron chromite exposure can lead to acute pneumonia. Chrome can be a carcinogen and extreme levels of exposure, especially to certain types of chrome compounds, can lead to death.


Cobalt oxide and carbonate are used as colorants in glazes, slips, and stains. Cobalt will enter the body through the skin and can cause liver damage and dermatitis.


Copper oxide and carbonate are used as colorants in glazes, slips and stains. It can enter the body through ingestion or inhalation.

Although a necessary element for bodily health, too much copper is toxic. It irritates the skin, eyes, and mucous membranes. Inhalation of dust or fumes can result in irritation of the respiratory tract. In some cases, copper poisoning can lead to cataracts.

Iron and Ferrous Sulfite

Iron, in various forms, is used as a colorant in clays, glazes, slips, and stains. Iron toxicity can include vomiting, upper abdominal pain, pallor, cyanosis, diarrhea, drowsiness, and shock. Children are especially susceptible to iron poisoning.

Ferrous sulfite can be fatal and should be avoided, especially since there are other, much more benign forms of iron available to potters.


Lead is a very powerful flux that enhances glaze coloration and smoothness. It is also a poison which will build up in the bones. It does not flush out of the system; lead can accumulate for years before a fatal level is reached.

If you must use lead, always use it in the form of lead frits. Never use raw leads, such as white, red, or yellow lead. These are extremely toxic. Never use any lead or lead frits in clay bodies, glazes, underglazes, or overglazes for any pottery that is able to hold food or liquid. Lead will leach out into foods and liquids.


Manganese is used as a colorant in clay bodies, slips, and glazes. It is most likely to enter the body through inhalation of the dust and fumes. The primary targets of manganese toxicity are the brain and the lungs. Manganese poisoning can result in pneumonia, paralysis, sleep disturbances, deficits in mental acuity, and can produce Parkinson’s-like symptoms. It can be fatal.


Nickel oxide is used as a colorant. It is very hazardous in case of inhalation, and hazardous in case of ingestion. Nickel oxide is also an irritant to both the skin and eyes. It is known to cause cancer and mainly targets the lungs.

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