|Monthly Tech-Tip |
The white and colored mugs are made using the G2934 base, the transparent and purple one using the G2926B base. These are fired to cone 6 using the PLC6DS schedule. This is M340S REV, a cone 6 buff stoneware with 0.2% 60-80 mesh granular manganese added. The body has been formulated to stop a little short of typical fired maturity to assure no blistering at cone 6 (a common issue with manganese speckle additions). Of course, one can wedge the granular material into a buff stoneware body but, again, choose one that is not too vitreous (or bloating could occur). Experiment with percentage and particle size to get the desired speckle density.
This is actually quite easy to do: Just wedge the clay over the manganese spread out on the board, when the board is clean turn the slug sideways and cut and layer about 20 times (to get 1 million layers). Then wedge normally. Only 0.2% manganese is needed (as a percentage of the dry clay). Since pugged clay contains 20% water it is easy to calculate the dry weight of this piece. For example, suppose this weighs 2 kg: 80% of that is 1.6 kg or 1600g. 0.2% of 1600 is 3.2 grams. Shown is the kind of mug I get. The outside glaze is G2934Y silky matte (opacified with tin) and inside glaze is G2926BW glossy white. It was fired at cone 6 using the PLC6DS schedule.
In ceramics, it is used primarily in clays and glazes to achieve fired speckle (including the brick industry).