Release of lead from typical Canadian pottery glazes

Abstract

In recent years intensive world-wide research began into the problem of release of lead and other toxic metals from glazed ceramic ware used for food and beverage service. One such study was conducted in the Mineral Sciences Laboratories, CANMET, to assess the instability of glasses melted from typical glaze compositions in contact with 4% acetic acid. The present study was made to determine the stability of typical Canadian pottery glazes under conditions simulating domestic use and to examine the mechanisms of Pb release and stabilization as a contribution to developing stable, safe glazes. Lead release from glazes in contact with 4% acetic acid was studied as a function of applied glaze thickness and firing temperature. It was shown that the amount of lead release was dependent not only on composition, but also on glaze thickness and firing temperature. The reported inhibiting effect of chromate additions was examined. It was found that lead release from copper-bearing glazes can be suppressed by adding about 0.5% m/m BaCr04 or Cr 203 . The inhibiting effect of the chromate compounds is attributed to modification of the glaze structure.