EFFECT OF TEMPERATURE AND PARTICLE SIZE ON THE DRYING CHARACTERISTICS OF A PORCELAIN MIX

A standard mix of table porcelain was prepared having the following recipe: 35% kaolin, 15% ball clay, 25% feldspar and 25% silica. Three different particle sizes of silica were used: fme particles of average particle size = 0.161 mm, intennediate particles of average size = 0.210 mm and coarse particles of average size = 0.303 mm. Samples were hand mol4ed using 54% water and dried at 45 ± 3% R.H. in a muffle drier with air circulation at temperatures ranging from 80°C to 130°C. Moisture content of samples was followed as function of time of drying and the rate of drying was calculated and plotted against moisture content. Results revealed that the rate of drying in the constant rate region increases with an increase in temperature and a decrease in silica particle size, while both the time duration of that period as well as the equilibrium moisture content decrease with an increase in temperature and a decrease in silica particle size. The critical moisture content also decreased with an increase in temperature. Samples display a drying shrinkage that increases sharply above a certain drying temperature except for coarse silica samples. It was also found that temperature affects drying characteristics more than does silica particle size.