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

Hi Ken,
I will try this, but the reason I use the hot gun is because the class is
only 2hr duration.

If when leaving the items in the college wet cupboards, you return to find
the cupboards were too wet and your hard work has been reduced to a soggy
mess, or they are too dry and has completely dried out leaving it too hard
to continue work on the following week.

So, because of this, what I always aim to do is complete whatever I start
that session - hence using the hot gun.

Also, I sometimes take the project home to finish off there. I hate leaving
items at the college as they are on constant display to all, often being
moved around, and sometimes we return to find broken pieces. The classrooms
are in constant use (by schools also), and we cannot always rely on the
college staff firing greenware on a regular basis. Sometimes items are left
for a couple of weeks in the kiln room waiting to be fired. I feel sorry
for those who dont have the ability to finish their items at home, like I
can.

However, I have done a test bowl and left it to dry there. I will see if
the results are any different.

If its sooo bad there then why do I attend the college? - Well I like the
company, its great to share ideas, and gain inspiration from others. Being
stuck in my own studio can be lonely, and can easily get stuck in a rutt of
making the same things over and over again. Its great to mix, have a laugh
in the process, try new ideas once in a while, and if you do get a problem -
well a problem shared, is a problem halved! But in this case, everyone is
baffled!

Perhaps too fast drying is the key here, but my ex-tutor used a blow torch
which was far more powerful (on the very same clay) and we had no problems
then.

I'll let you know how the bowl turns out!

Keep the ideas flowing!

JM