|
Garth,
Hard to say if it was human or mechanical error. If it is a cone 6 clay, it should never have gone beyond its maximum temperature of 2232 degrees (F) or it will literally melt to glass. If it is a cone 10 clay that was fired at that temp, it should still be OK. If a cone 10 clay is fired at cone 11, that will cause the same problems. The cone number signifies the absolute maximum temperature that is reached, not a degree more, and the kiln should automatically shut off at that point to keep the temperature from raising any more.
Was the base actually glass - like, or could it be that the piece was set on a dirty shelf that had residue of melted glazes off of other fired pieces and only the very bottom was glassy?
What did you use to smoothe your surface? If it was just a sponge and water, that wouldn't change the color - but any other substance might.
|