|Monthly Tech-Tip |
These two bowls are L4558, a 70:30 mix of M370 and IMCO C-Red clay. They were fired to cone 6 using the C6DHSC slow cool schedule. The left bowl is glazed with our standard G2926B, it contains about 20% frit. It is fluxing the clay surface, transforming it to an ugly brown (which is what that body looks like when fired to cone 8). The amber transparent GA6-B Alberta Slip glaze on the right is not doing this at all, even though it also contains 20% frit. In addition, it is much glossier. Both bowls have underglaze sprayed banding, the GA6-B is transmitting that better also.
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.