|Monthly Tech-Tip |
Bloating. These teapots have been refired to cone 6. This is just a standard porcelain body (feldspar, kaolin, silica, ball clay) that vitrifies fully at about cone 7. The slower the firing the more likely this is to happen (refires must be done more slowly to avoid dunting). This type of bloating is not easy to explain, only a few mitigating measures are obvious (putting ware in a cooler part of the klin, avoiding glazes of very high boron content, using a stoneware or whiteware instead of a porcelain, using higher quality body materials).
Refiring pottery and porcelain comes with many issues that can ruin ware, knowing about these will help you do it successfully.
The term vitrified refers to the fired state of a piece of porcelain or stoneware. Vitrified ware has been fired high enough to impart a practical level of strength and durability for the intended purpose.
Bloating occurs when the off-gassing of decomposing particles in a body has not completed by the onset of density and impermeability associated with the vitrification process.