These bars were fired at cone 10, they were straight when dry. The back one is a cone 10 Grolleg body, the front one is a cone 6 Grolleg body. This simple test is valuable to determine susceptibility to warping in porcelains. If the pyro-plastic deformation is too much, for example, the weight of a handle will pull the round rim of a mug into an oval shape, for example.
The term vitrified refers to the fired state of a piece of porcelain or stoneware. Vitrified ware has been fired high enough to make it very strong, hard and dense.
Warping is a defect encountered in the firing of ceramic ware. Typically the profile of the ware is too extreme for the degree of vitrification of the body.