DEFORMATION - A defect during firing.
Deformation is the changing of the shape caused by stress or strain of overheating when firing pottery. The result can be caused by firing temperatures being too high, so that the work in the kiln can no longer keep its shape. It can be caused by impure clay or faults in the construction of the work and it is most noticeable in flat objects like tiles. Kiln shelves can bend but the standard of kiln ware is now so good that this seldom occurs; it is more likely to happen in hand made work.