In the winter of 2002-2003 I had a wood stove and a gaz heater on all day. However the temperature used to come drastically down during the night. One bisque firing came out with a crack under each pot in the form of an S like a Zorro sign with a spelling mistake! From then on I decided not to fire bisques during the winter at all.
I've decided to try a glaze kiln.
At first I put the stuff on both sides of each shelf. A bad idea. After a while, it gets hard and flakes of it fall down on the nice glaze of a pot on the shelf below.
Now I use one side of a shelf without any product for bisk firing and the other side with the stuff for glaze firings only.