Reduction of Lead Leacing from Porcelain Overglaze Decoration by Firing in a Water-Vapor Atmosphere

Recently, the amount of lead leaching from tableware has come under strict regulation. Firing in a watervapor atmosphere has been shown to reduce greatly the leaching of lead by some investigations. However, the mechanism of the reduction of lead leaching has not been discussed. In this study, the effectiveness of water-vapor in reducing the lead leaching was confirmed. Furthermore, in order to understand the role of water-vapor in reducing the lead leaching, the amount of lead vaporized from PbO and lead-containing glasses was measured between 750 and 900°C in dry and water-vapor atmospheres. The amount of vaporized lead increased about ten times in the water-vapor atmosphere for PbO. For the lead-containing glasses, the enhancement of lead vaporization was also observed in the water-vapor atmosphere. The change of surface composition due to the vaporization of lead is thought to be the cause of the observed reduction in lead leaching.