Blow Out Big Time - sometimes even cooked rice does not work!

This is one time when even cooked rice added to my paperclay did not survive the bisque fire. Large chucks from the sides of my hand pinched bowl blew out during the bisque fire. I cannot figure out what is causing this as the piece was bone dry when it entered the kiln. It had also been drying in my studio for several weeks prior to the bisque fire. These kind of failures happen once in a while (about 5 - 10% of the time) and I'm still trying to find out the common underlying factor.

I use left over cooked rice and sometimes I let the rice dry out for several days. When I leave the rice out for too long, they start to dry out and get hard and crusty. Then I rehydrate them to soften them up again so I can wedge them with my paperclay. Could this affect the outcome? Perhaps some moisture still remains within the clumps of rice causing the blow out.

This method of making my hand-formed bowls and cups takes so much longer to make than if it had been thrown on a wheel. The successful end product, however, it worth the effort.