Lead Release from Glaze during Firing in a Water-Vapor Atmosphere

Amount of lead release from glaze, changes of the lead concentration distribution and structure in the surface layer of the glaze during firing in a water-vapor atmosphere were investigated. Lead ions in the surface layer of the glaze were released by surface exchange reaction of proton or hydronium ions in water vapor and lead ions at the surface of the glaze during firing in a water vapor atmosphere. Then the proton or hydronium ions which were introduced by the surface exchange reaction were released as water vapor by dehydration reaction, and the silica-rich layer was formed at the surface. This silica-rich layer comes to a protection layer and which makes waterproof of porcelain tableware.