Many glaze formulas have traditionally used lead as a major element. Even though they can leach into liquids and meals, you should always remember this whenever you are choosing food-safe ceramics. The risk comes from the cumulative consequences of using common functional items continuously. Since most practical ware is fired to higher temperatures, lead, which is widely employed as a flux (melting agent) in lower fired glazes, will either not be present or will have been burnt out during the glaze firing. If you have any doubts or concerns about lead contamination, you should always ask before buying pottery.