Expert: Sam Kelly - 12/20/2008

Question
My helper didn't close my kiln all the way and the cone 6 duncan clear glaze bubbled and looks frosty on the pieces. Can I just refire them? Should I coat them again? The pieces are a cassarole dish and lid and small jewelry boxes with lids.

Answer
Hi Joan, all you can do is refire as they are. What you are seeing is an under fired pot, did not get to temp.
Refiring will bring it all together for you, there may be slight differences than pots fired correctly the first time so I suggest a soak at top temp. To let everything bubble up and settle down before cooling down.
You need a guard cone to watch, one cone higher that you want to fire to, as soon as cone 6 goes down back the heat off( not very much) so it does not get any higher(stays the same)and let it soak at that temp. When the guard cone is half way down turn the kiln off. Do not soak for more than 1 hour no matter what, even if the guard cone has not mooved.
I use gas so I can do these things, if you have electric you will just have to play and watch.

Sam