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Hazards in Pottery: Glaze Toxicity

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A few things may be largely overlooked in pottery and ceramic arts making; possible hazards. While there are many possible hazards in every step and in materials used for pottery art; from the clay itself, to glaze and pigments, all the way to firing techniques that can be hazardous to the health of the potters as well as users/customers. Which is why it is SUPER important to learn and get educated.

This time we’ll be focusing on the possible hazards of glaze toxicity and how to avoid them. This is especially important in making tableware pieces, so as not to endanger yourself and customers.

courtesy of Parkland College

Glazes are usually a mixture of silica, fluxes (to lower the melting point of silica), and colorants. Common fluxes are lead, barium, lithium, calcium, and sodium. When it comes to luster or metallic glazes that are fired in reduction atmosphere, these glazes often contain arsenic, mercury, and other highly toxic solvents. There are many reported cases of lead poisoning from ceramic making and from Leaching in tableware (when dangerous substances are transferred into food through tableware). These hazards can definitely be avoided, if handled with care and caution.

Manganese in a clay body. courtesy of

-Lead compounds are highly toxic by inhalation or ingestion. Symptoms of lead poisoning include damage to the nervous system, kidney, anemia, and more. Lead CAN LEACH especially in tableware IF not fired properly or the glaze composition is not correct. Lead can also leach through contact with acid or acid in food. It is very important to understand the composition of the glaze used or avoid this substance completely in tableware making.

-Glaze that are labeled as (lead-safe) means that it won’t leach after firing. However, it is still toxic during handling and making process, take extra precaution in the studio.

-Barium and Lithium are also highly toxic through inhalation, make sure you use masks in the studio to avoid health hazards.

-Some colorant compounds of certain metals such as Arsenic, Beryllium, Cadmium, nickel, and uranium are known to be human carcinogens.

-Cobalt, Lead, Lithium, and Manganese (often present in clays and pigments/glaze that are dark in color) are toxic by inhalation.

courtesy of Amaco Brent

There are definitely precautions that can be taken to avoid these health hazards. In making tableware, you can choose to use glazes and pigments (colorants) that are “Lead Free” to avoid leaching. It is best to only use lead glazes in non food ware pieces.

Also learn the composition of the glazes and how much (in percentage) of these substances can be used in production and future use for consumption. To find out the content of the glaze you purchased, you can directly ask the producer. Not to mention, learn the correct technique of firing when using certain glazes is very important.

These are various health hazards that are present in pottery making. This does not mean you have to avoid them altogether, but it only shows how important it is to be educated and keep learning more about the materials that you are using. In the end, it’s for your safety and your consumers!

Enjoy exploring pottery

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