A term used in the ceramics industry to signify the degree of vitrification in a fired clay. Mature clays are dense and strong, immature ones porous and weak.
The term Terra Cotta can refer to a process or a kind of clay. Terra cotta clays are high in iron and available almost everywhere. While they vitrify at low temperatures, they are typically fired much lower than that and covered with colorful glazes.
When clay materials and bodies bubble as they melt or over fire. This normally happens in raw materials that contain particulates that produce gases during firing.
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.