AN INVESTIGATION OF THE POSSIBLE USE OF CERTAIN CALIFORNIA CLAYS IN VITREOUS CHINA SANITARY-WARE BODIES1

Abstract

A bonding clay from Riverside County, a plastic fire clay from Placer County, and a washed, white-firing clay from Amador County, were tried in vitreous china sanitary- ware bodies. Descriptions and properties of the clays are given. Twenty trial bodies were tested. The bonding clay and the plastic fire clay were found unsatisfactory for use in this class of ware. Based on laboratory tests, the use of the washed clay from Amador County, to the extent of 10 to 30% of the body mixture, is quite feasible. This would reduce the total production cost of ware manufactured in California plants by 1.0 to 2.5%, depending upon the location of the consumer and the proportion of local clay that can be utilized. A body containing 30% of the washed California clay and no English china clay proved to be as good as the standard type body used for comparison; while another mixture, containing 18% of the washed clay, was superior in many respects to the standard body. The effects of additions of ground biscuit, magnesium and calcium carbonates, and sodium chloride, were also determined. Subsequent commercial tests in a whiteware plant showed that under the conditions prevailing in that plant, from 10 to 15% of the California clay was the maximum that could be used without increasing the vitrification temperature of the body. In this case, the California clay displaced a mixture of china clay and ball clay, rather than the china day alone. It was also necessary to alter slightly the silica-feldspar ratio.