I would suggest you allow your ware to dry normally( Slow) Or change your
clay body formulation . Your rapid drying has not cracked pots but rather
created stress lines that turn to cracks upon bisque firing . Glaze firing
rather than curing problem only applifies it as there is difference of
expansion during firing that further stresses cracks in ware . Try same clay
body dried slower or another formulation that isnt as stress sensitive to
rapid drying .
Good Luck
Ken
"JM" wrote in message
...
Hi all,
I have a problem which has left myself, and my pottery teacher as puzzled
as
the pots.

Recently my ware has developed fine hairline cracking during bisque
firing.

All ware is thoroughly dried before firing (when pots are both fired at
college and at home) - so I don't damp is not the problem. One of the
items
has been on the drying shelf for about 2 months!

I have been using a hot-air gun to get some pieces to leatherhard stage
for
turning, but have not held it too close - I know a potter who even uses a
blow torch. So I am not even sure that this is the problem creater.

Thinking that when glazing the glaze might seep in and seal the fine
cracking, but the second firing being hotter opens them up even more.

The cracks are not localised and run in all directions, so are not caused
by
lack of compression.

If I can't get to the bottom of this irritating and frustrating condition
I
could always start a line in jigsaw pots.

Please come up with suggestions of possible causes - as I have exausted
all
known possibilities.

JM