Ceramics art has a wide variety of hazards. The specific hazards and precautions
may include working with clay, glazing and coloring, firing in a kiln, and potential
leaching of finished ware.
Clays are minerals composed of hydrated aluminum silicates often containing large
amounts of free crystalline silica. The primary health hazard is from repeated breathing
of clay dusts which can cause permanent scaring to lung tissue. Excessive dusts occur
when dry clay is mixed without ventilation or allowed to accumulate on surfaces.
Safety guidelines to minimize exposure to clay dusts:
Alleviate back strain and wrist injuries by practicing good work habits:
- Adjust wheel height to enable work with your back straight.
- Avoid heavy lifting
- Avoid repetitive motions by varying your daily routine.
Glaze contains a mixture of silica, fluxes and colorants. Fluxes and colorants can
be highly toxic by inhalation. Highly toxic glaze constituents include: Antimony,
Arsenic, Barium, Beryllium, Cadmium, Chromium, Cobalt, Lead, Lithium, Manganese, Nickel,
Uranium, or Vanadium.
Safety guidelines to minimize exposure to toxic glaze:
- Use lead-free glazes. If the glaze does not state “lead-free” or “leadless” on the
label, assume it contains lead until proven otherwise.
- Avoid using colorants that are known or probable human carcinogens (arsenic, beryllium,
cadmium, chromium Vanadium, nickel, and uranium). There is no known safe level for
- Know what you are working with. Read the safety data sheet and understand the hazards.
- Mix and weigh glazes in an exhaust hood. Wet glazes are not an inhalation hazard.
Use a wet mop to clean spilled powders.
- Wear gloves when handling wet or dry glazes.
- Perform all glaze spraying in a ventilated booth.
- Wash hands thoroughly after each use.
- Electric kilns and fuel-fired kilns are used to heat the pottery to the desired firing
temperature. Fuel-fired kilns are heated by burning gas (natural or propane), oil,
wood, coke, charcoal or other materials. The fuels produce carbon monoxide and other
combustion gases. Fuel-fired kilns are usually vented from the top through a chimney.
Firing temperatures can vary from as low as 1382°F for raku and bisque wares, to as
high as 2372 °F for stoneware, and 2642 °F for certain porcelains.
- The early stage of bisque firing involves the oxidization of organic clay matter to
carbon monoxide and other combustion gases. Sulfur breaks down later producing highly
irritating sulfur oxides. Also, nitrates and nitrogen-containing organic matter break
down to nitrogen oxides.
- Galena, cornish stone, crude feldspars, low grade fire clays, fluorspar, gypsum, lepidolite
and cryolite can release toxic gases and fumes during glaze firings. Carbonates,
chlorides, and fluorides are broken down to releasing carbon dioxide, chlorine, and
- At or above stoneware firing temperature, lead, antimony, cadmium, selenium and precious
metals vaporize and the metal fumes can either escape from the kiln, or settle inside
the kiln or on ceramic ware in the kiln. Nitrogen oxides and ozone can be generated
from oxygen and nitrogen in air.
- Only personnel who have been instructed in firing procedures may operate the kilns.
A complete understanding of firing procedures and safety components is essential to
avoid personal injuries or damage to the kiln.
Processes such as Raku Firing and Salt Glazing present unique safety hazards and should
only be done outdoors away from air intakes or open windows of buildings. Close faculty
or graduate assistant supervision is required at all times.
Salt glazing involves throwing wet salt into the heated kiln while the bisque ware is being fired.
If sodium chloride salt is added, hydrogen chloride gas is formed which is highly
toxic by inhalation. Hydrogen chloride and water vapor also form corrosive hydrochloric
acid which can corrode metal fittings in the area. Sodium carbonate should be substituted
for sodium chloride as carbon dioxide gas is generated instead of hydrogen chloride.
Raku firing involves firing ware at a low temperature in a regular gas kiln and then removing
the hot pieces and placing them in sawdust, leaves, or other organic materials for
the reduction phase. The reduction phase releases large amounts of smoke and carbon
monoxide and treated materials can also produce highly toxic compounds.
In the event of a kiln-room malfunction (smoke, odor, flame outside kiln, or water
leaks on electric kilns) immediately notify Ceramics staff. In an emergency, evacuate
the studio and contact campus emergency services (828-227-8911).
All mechanical equipment is to be equipped with guards that prevent access to electrical
connections or moving parts, such as belts and pulleys of a vacuum pump. Each worker
should inspect equipment before using it to ensure that the guards are in place and
functioning. Careful design of guards is vital. An ineffective guard can be worse
than none at all, because it may give a false sense of security. Emergency shutoff
devices may be needed in addition to electrical and mechanical guarding. Please reference
the Machine Guarding Program for more information.