Definition:Vitreous

Vitreous — or vitrified — describes a ceramic body that has been fired to a temperature high enough for the clay particles to partially melt and fuse into a dense, glass-like, non-porous mass. Porcelain and stoneware are vitreous; earthenware is not, which is why earthenware requires a glaze to be waterproof. Vitrification is what gives fine porcelain dog figurines their characteristic hardness, translucency, smooth surface, and resistance to staining — qualities that distinguish them from the more porous earthenware body used in Staffordshire and similar traditions. The degree of vitrification varies by clay body and firing temperature: hard-paste porcelain is more fully vitrified than soft-paste; high-fire stoneware is vitreous while low-fire earthenware is not. When examining an unglazed area on a ceramic dog figurine, the density and smoothness of the exposed body indicates whether the piece is vitreous.