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Safely Handling Clays and Glazes

Clay:

Clays are composed of minerals composed of silicates, often containing varying amounts of crystalline free silica. Depending on the source of the clay, the minerals it may contain true clays, sources of silica, and small amounts of additives to impart color, prevent mold, or give texture.  Additionally, some clays may contain materials such as metal oxides, vermiculites, talcs, and fire brick.

While clays are not considered hazardous by themselves, working with the material over time can expose the artist to some potential hazardous conditions.  The primary hazard associated with clay occurs when mixing dry clays or when wet clay begins to dry.  The fine dust that results from dry clay may contain silica, which presents a respiratory hazard to the artists.  Any process that creates or involves exposure to dust should be minimized or avoided.

Artists should strive to work in well ventilated areas when working with clay.  If possible, the artist should work with pre-mixed clays.  When working with dry clay, the artist should employ wet methods to prevent exposure to the dusts.  Additionally, the artist should use wet methods (sponges, mops) when cleaning floors and surfaces after working with clays.  Sweeping should be avoided.  If a vacuum is used in the studio, it should be fitted with a HEPA (high efficiency particulate air) exhaust filter to help prevent dusts from re-entering the air.  

Finally, if the artist chooses to use respiratory protection, they must schedule a respiratory fit test with EH&S to ensure that the proper respiratory protection is chosen for the task at hand.  For more information, contact EH&S at x4-8749.

Glazes:

Glazes that are used to color or finish clay pieces typically contain a mixture of silica, fluxes, and colorants.  Common fluxes may include lead, barium, lithium, calcium and sodium, and are used to lower the melting point of silica.  The actual colorants, which are an assortment of metal oxides, such as chromium, cadmium, antimony, and nickel, usually account for a small percentage of the glaze by weight. 

Glazes present exposure hazards during the application of the glaze to the substrate.  The artist should strive to apply the glaze by hand in a well ventilated area.  The use of sprays to apply glazes should be discouraged, but if necessary, the area should be well ventilated and the artist should wear proper personal protective equipment.  Additionally, the artist should be careful when using glazes containing lead on clay pieces intended to be used with food.  Improperly fired glazes may cause the lead to leach out of the clay piece and into the food item.  Care should be taken to read and follow the manufacturer’s instructions when using glazes with lead.

Finally, because of the toxicity of some glazes, care must be taken to ensure the proper disposal of such glazes.   As with all materials used in the studio, an SDS must be made available for each different type of glaze used.

Waste materials must be placed in a properly labeled container and closed when not in use.  
The waste will need to be disposed of properly through EH&S through the chemical/hazardous waste pickup form. 
Please refer to our hazardous waste guidelines, the 5Ls, for further guidance.  
If you have specific questions as to how to dispose of your waste, please consult your Safety Coordinator or Environmental Health & Safety at x4-8749.