|Monthly Tech-Tip |
The glaze is G3933A, and the clay body is Plainsman Coffe Clay. The front tile was fired using the C6PLST schedule that just goes to cone 6, holds for a short time and then free falls. The body is stained with raw umber, that material has a high LOI and gases right around cone 6. During the short hold at cone 6 the glaze percolated and foamed up with bubbles. The shut-off froze that in place. The mug behind was fired using the C6DHSC drop-and-hold and slow-cool-firing. The drop-and-hold shuts off the gas expulsion of the umber and gives the glaze a chance to shed the bubbles. The slow cool gave it lots more time to smooth out and heal every single pinhole - the result is dramatically better.
A kiln firing schedule where temperature is eased to the top, then dropped quickly and held at a temperature 100-200F lower.