Hi, I have just had three pieces come out of my most recent glaze firing and all three looked beautiful coming out of the kiln, then about 24 hours later formed a large ugly hairline crack from the rim of the pot all the way down to the base. I am a relatively experienced potter, I have never seen or had this issue. I am not opening the kiln until it's cool. Anyone know what's going on?
One bowl had a commercially prepared glaze, the other two were my own mixed glazes.
Thank for your help,