|Monthly Tech-Tip |
The clay is Plainsman M370. Fired at cone 6 using the PLC6DS drop-and-hold firing schedule. The inside glossy glaze is G2926BL. The outside glaze base is G2934BL matte. Both recipes contain 6% Mason 6600 black stain. G2934 is tricky to keep consistent because the matte surface is a product of both the chemistry and the firing schedule. Thus we faced lots of testing when it became necessary to substitute Ferro Frit 3124 for the supposed equivalent, Fusion Frit F-19. Early results showed a little better melting, so the 10-15% glossy we normally add to move the stoney matte toward satin is not needed. However, we still made an 85:15 batch for our more frequent slow-cool C6DHSC firings (otherwise this G2934 mug would have fired too matte). So with the two recipes and two schedules I can produce four surfaces, from gloss satin to stony matte.
This is G2934BL glaze fired using the C6DHSC slow-cool firing schedule, this has enabled too much crystallization. This mark cannot be rubbed off, matte black glazes show the marks more than others. If I had fired it using the PLC6DS free-fall schedule, it would have been glossier. Or, I could blend in a greater percentage of the glossy black. This being said, for this type of piece some cutlery marking can be tolerated.
Random material mixes that melt well overwhelmingly want to be glossy, creating a matte glaze that is also functional is not an easy task.