But the potter is not the only one in danger. If the glaze is not well formulated and not fired to high enough temperature , lead can leach from the glaze into foods the pottery is used for. Acidic foods such as fruit juice, wine or vinegar can leach lead from a glaze quickly, but even a bland pot of beans can collect some lead compounds as the heat of cooking accelerates the process. How much lead leaches out of a lead-glazed utensil depends on how the pot was made. Again, lead may be a minor component of the glaze, or it may be covered with a harmless non-lead glaze which effectively seals off the poison compounds.
Modern ceramics made by reputable commercial firms are usually harmless.
Such firms have never used lead glazes, have given them up decades ago, or place them under safe glazes where they are rendered harmless. Neither does the problem lie with commercially imported pottery. In addition, FDA regulations mandate that imported items not safe for food-use must have a permanent stamp to that effect, usually on the bottom of the piece. The problem centers chiefly around pottery made by artisans or folk-potters in other countries and brought into the U.S. by individuals for their personal use. In some homes, the family cazuela or cooking pot is an heirloom, passed from mother to daughter.