Jar with Stuck LidWhen I made this lidded jar I forgot to put paper or cloth between the jar and the lid while the clay dried. The result is that the lid stuck to the rim of the jar. Since I had not done anything to make it a strong connection- like slipping and scoring, I figured the lid might come free in the firing where a poor connection will usually separate. Of course, it'll only come apart if you DON'T want it to.
If air pockets explode in the kiln this would have blown up, but it didn't. Actually, I've been unable to get it to separate at all. So sad.
So what makes pots blow up? Moisture. As the water expands from the heat of the kiln it needs room and breaks apart the clay. It's the worst enemy of a pot in the kiln. If you make sure the clay is completely dry before you get the kiln over 212 degrees Fahrenheit you should not have any problems.