Spodumene as a Flux Component in Sanitary Chinaware Bodies

Four groups of body compositions involving partial replacement of feldspar by spodumene were investigated. In the first group the firing temperature was maintained constant and the clay content was increased at the expense of the flux. In the second group the flint, clay, and total flux (flux was 20y0 of the body) contents were held constant and spodumene replaced 19, 30, and 40y0 of the total flux. In the third group the flux content containing varying proportions of spodumene was increased from 20 to approximately 40% of the body at the expense of flint and the firing temperature was lowered. In the fourth group miscellaneous bodies containing a variety of fluxes, including flotation soda feldspar, nepheline syenite, talc, and whiting in addition to the potash feldspar and spodumene, were tested. The spodumene appeared to have little advantage in lowering the maturing temperature of the 20% flux bodies; however, a spodumene: feldspar ratio of 30:70 appeared to lengthen the firing range. The effectiveness of the spodumene increased as the total flux was increased. A body containing 27% of flux matured at cone 11–12 when potash feldspar alone was used and at cone 8 when 8% of the feldspar was replaced by spodumene. A body containing spodumene, talc, and nepheline syenite matured at cone 3–4 and had a fired modulus of rupture in excess of 10,000 lb. per sq. in. The small amounts of spodumene (up to 8% of the body) had no apparent effect on the stability of the casting slips or similar properties.