Abstract
ABSTRACTPurpose.—The effects of CaO content in clay between 0.15 and 8.22% and the salt glazing temperatures between cone 02 and 10 on some properties of salt glazes were studied.Brightness.—As low as 1 % CaO will prevent clays from taking a bright glaze at low temperatures. Clays containing CaO can best be glazed at high temperatures, above cone 5, providing the Fe2O3 content is low. The type of glaze a clay containing CaO will take may be approximately predicted by calculating G in the following equation in which x1 x2, x3 and x4 represent the percentages of Al2O3, SiO2, Fe2O3 and CaO in the calcined clay and T represents the salt glazing temperature in °C. image When G is greater than 0, bright glazes were produced, when between −0.1337 and 0, semi matt glazes were obtained and when below −0.1337 matt glazes were produced.Color.—Clays high in both CaO and SiO2 produced greenish yellow glazes at cone 7 on clays containing 5.32%, Fe2O3 as is represented by the following equation: image When A is greater than 0, the greenish yellow glazes were obtained.Thickness.—Raising the salt glazing temperatures and lime content increased the thickness of the glassy and fused portion on the surface of the clays.
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