|Monthly Tech-Tip |
The body is Plainsman M390. These are commonly-used base glazes. The top one is an MgO matte, next down is a calcium matte. They react very differently to these additions. Notice also the difference when titanium dioxide is applied thickly. Tin oxide fires whiter than zircon (e.g. Zircopax). Each opacifier has issues. Tin is expensive. Titanium is difficult to mix into the slurry (screening required), not as white or opaque, variations in thickness produce more difference in results and it can turn blue. Zircon is more likely to cutlery mark, twice as much is required and it amplifies the color of any iron present.
This mug was thrown. But the handle was cast from L4005D, a recipe for an M390-compatible casting body you can make. The fired maturity of this (fired shrinkage and porosity) matches very well with M390. The casting process is superior for certain shapes and ware types (this sacrifices no casting properties because there is no iron oxide in the recipe, it uses Redart instead). These are strong, the handle on this glazeless mug endured a couple of good taps with a hammer and stayed solid. The body fires a little browner in color than M390, which is a product of using Redart, a low-temperature clay, but as long as ware is glazed it looks identical.
Glaze opacity refers to the degree to which it is opaque. Opacifiers are powders added to transparent ceramic glazes to make them opaque.
G2934 - Matte Glaze Base for Cone 6
A base MgO matte glaze recipe fires to a hard utilitarian surface and has very good working properties. Blend in the glossy if it is too matte.
G1214Z1 - Cone 6 Silky Matte
This glaze was born as a demonstration of how to use chemistry to convert a glossy cone 6 glaze into a matte.
G2934Y - Cone 6 Magnesia Matte Low LOI Version
The same chemistry as the widely used G2934 but the MgO is sourced from a frit and talc instead of dolomite. It has a finer surface, less cutlery marking and staining.