Ceramic art and pottery has a wide variety of hazards. The specific hazards and precautions can be divided into four areas:
- working with clay
- firing in a kiln
- glazing
- potential leaching of finished ware
Working with clay
It is important that you do not contaminate or add any other product or substance into the clay we provide. The only allowable additions to clay are clean water, vinegar (used in slip) or underglazes. Please do not use underglazes without checking with us first, as use of underglaze may affect our ability to kiln fire your work. Also, it is important that you only use clay provided by us If you have clay other than that provided by us, please check with us first before sending for kiln firing.
Clays contain minerals composed of hydrated aluminum silicates and may contain large amounts of crystalline silica. Other impurities may include organic matter, sulfur compounds, ground firebrick, sand, talc, vermiculite, perlite, and small amounts of minerals such as barium carbonate and metal oxides.
As a consequence, working with clay may give rise to a number of hazards which may include:
- There have been known cases of silicosis, or “potter’s rot, from chronic inhalation of large amounts of free silica from clay dust. Silica dust exposure is not known to be hazardous by skin contact or ingestion.
- Chronic inhalation of kaolin is moderately hazardous, and can result in kaolinosis, a disease in which the lungs become mechanically clogged.
- Sand, perlite, grog, and vermiculite contain free silica and are, therefore, highly toxic by inhalation. Vermiculite may be contaminated with asbestos.
- Bags of clay and glaze materials can be very heavy, and lifting can cause back problems.
- Hypersensitivity pneumonia, asthma, or other respiratory problems may occur with exposure to molds growing in wet clay that is being soured or aged in a damp place, in slips that stand for months, or with inhalation of dry aged clay. Molds can cause or exacerbate skin problems and change the workability of clay.
- Hand building with clay for long periods of time could result in carpel tunnel syndrome because of the awkward position of the wrists. Pain, numbness and/or pins and needles in the thumb and first three fingers, are common symptoms. Back problems can occur from bending over work spaces, standing or sitting and inadequate work area ergonomics.
- Hand contact with wet clay can result in abrasion and dryness of fingertips and hands.
- Tools may cause cuts and abrasions.
- Clay scraps on the floor, bench and other surfaces can dry and pulverize, producing an inhalation hazard due to the presence of free silica. Similarly, reconditioning clay by pulverization and sanding finished green ware, can create very high concentrations of hazardous silica dust.
Precautions to reduce risks
- Use premixed clay to avoid exposure to large quantities of clay dust.
- Store clay in a sealed bag or container and away from food preparation and eating areas.
- Avoid working with clay in food preparation or food consumption areas. If you must work at home near these areas, it is very important to wipe down and clean any work areas thoroughly (i.e. to reduce the risk of dry clay powder and dust forming)
- Use safe lifting practices for any heavy items. To prevent back problems, always lift with knees bent.
- Use caustion when using tools that could cause abrasions or cuts
- Wear separate work clothes Avoid materials and designs that may trap dust. Wash these clothes weekly, and separately from other laundry.
- Avoid contact of clay with broken skin. Use a skin moisturizer.
- Exercise and massage may relieve minor muscular pain.
- Keep wrists in unflexed position as much as possible to prevent carpel tunnel syndrome.
- Take frequent work breaks.
- If reconditioning, cut still-wet clay into small pieces, letting them air-dry, and soak in water.
- Finish green ware (that is clay work that has not yet been kiln fired) while still wet or damp with a fine sponge instead of sanding when dry. Do not sand greenware containing fibrous talc.
- Wet mop floors and work surfaces daily to minimize dust levels and prevent dry scraps from becoming pulverized. N95/P2 masks are recommended when cleaning dry clay and dusty areas.
Firing in a kiln
Our kiln technicians carefully manage the primary risks associated with kiln firings. To help us reduce the risks, as stated above, do not add or mix anything into your clay. Use clay and glazes provided by us. Remove newspaper from work. Do not sand kiln fired work. When handling after kiln firing, always wash hands afterwards.
Glazing
Glaze is a mixture of ceramic material containing, water, non-leaded frits, clay, and other minerals and
color pigments. Glaze may contains potential carcinogens, such as Crystalline silica (quartz). An inhalation hazard may be present if:
a) Unfired, dried glaze is excessively handled and allowed to create dust.
b) Mist is present after spray application.
A few pigments may contain small amounts of zirconium encapsulated cadmium and other metals. Other typical ingredients present have no known acute toxicity.
We recommend referencing and reading the glaze manufatoruers product guides (example).
Use similar precautions for working with glazes and outlined above when working with clay.
Potential leaching of finished ware
Works that have been kiln fired must not be used for food or beverages unless they have been glazed appropriately with lead-free non toxic food safe glaze.
References:
https://www.ceramicsstudio.coop/advice-for-working-with-clay-at-home
https://walkerceramics.com.au/health-safety
https://ehs.princeton.edu/health-safety-the-campus-community/art-theater-safety/art-safety/ceramics
