When most people think of porcelain, they think of a velvety translucent white surface. But Gillian Parke was interested in that white surface, but with a little more texture.
In today’s post, Gillian shares her technique for getting a very coarse surface texture from a clay body typically chosen for its creamy smooth consistency. – Jennifer Harnetty, editor.
I usually work in stages on a set of pieces using Highwater Clay’s Helios porcelain with coarse Custer feldspar (1-10 mesh, Seattle Pottery Supply) and 50-80 mesh molochite wedged in. Throwing with the inclusions requires using a substantial amount of water to provide sufficient slip for lubrication. This helps prevent both finger cuts and tears in the turning clay. However, the piece will lose its strength and collapse due to the low plasticity of porcelain if too much water is used.
Each stage is thrown on the wheel and allowed to dry. Before removing the piece from the wheel, the feldspar and molochite matrix is exposed with a metal rib or trimming tool. This also serves to remove the surface slip. After assembling the piece, it is completely dried and wax resist is painted onto areas that will eventually be glazed. Underglaze is then applied to the unwaxed clay areas. The underglaze is removed from the surface with a damp sponge, leaving an underglaze patina that accentuates the feldspar and throwing lines.
Wax resist is again applied to the dry surface. Using a needle tool, lines are etched through the wax, revealing the clay below. After wiping clean with a damp sponge, black underglaze is applied to the inlaid line. After bisque firing to cone 07, wax resist is applied to black inlay lines so that glaze will not cover the line and affect the color. Glazes are applied by pouring, dipping and/or brushing. The resulting piece is then fired in a gas kiln to cone 10 in reduction.
Feldspar inclusions result in pearl-like eruptions covering the surface of the vessel. This surface is painted with various luster overglazes and fired in an electric kiln to cone 017 multiple times per layer of surface treatment.