any chance your clay has been contaminated with another clay? when i do
glass and mix some from different manufacturers, different coe can cause
random cracks. or doesn't clay do that?
Charles,

Well, I cant say about the clay at college. It IS possible that the clay
has been contaminated there. To be honest the way they reclaim clay isn't
in the best controlled circumstances, and I have often found bits of metal
in the clay that I have been throwing (v dangerous - and nearly slashed my
hand open once). I do check the clay thoroughly for foreign objects now!

As for the teapot, I threw this approx 2 - 3 months ago, and has sat on the
shelf whilst other items got priority. I cannot remember whether I used my
own clay, or the colleges.

So I suppose that contamination may be the key, but I have not seen this in
other students' work.

I leave my mind open.....

Thanks for the response.

JM