The effect of copper oxide addition and the heat treatment temperature on the microstructure of zinc containing soft porcelain crystal glazes
There have been a number of detailed studies on soft porcelain glazes containing zinc oxide (Karasu et al 2000 and 2001, Karasu and Turan 2001a and b). In those investigations, both the effects of heat treatment parameters and additions of different type of colouring agents (such as CoO, CuO, Μ ηθ2, T1O2 and Fe203) into glaze compositions on the macro and micro-structure of final products were studied. Colouring agents play a role of fluxing at glaze maturing temperatures. Therefore, high fluidity of coloured glazes facilitates crystallisation on cooling. It was reported that higher crystallisation temperature (1180°C) produces plate-like zinc crystals unlike lower temperature (1080°C) leading to spherical shapes in soft porcelain glazes. No matter what colouring agent is incorporated into the glaze, these two types of formation does not change.