|Monthly Tech-Tip |
Each of these fired fragments is made from a mix of 65 ball clay and 35 nepheline syenite. These are the remnants of a DFAC test done on each (soluble salts concentrate on the outside edge of a disk as it is dried with the inside protected). Clockwise: Spinks Blend, 54S, OM4, M23, Gleason and KT1-4. Each of these ball clays produced a zero-porosity dense fired ivory porcelain at cone 6, they all have remarkably similar appearance. And they all have a high level of soluble salts.
In ceramics, certain compounds in clays and glazes can dissolve into the water, then on drying these are left on the surface.