Unlike porcelain glazed pottery is not completely fused together – the glaze is one layer, the body another. Both have different physical features, like density, flexibility, etc. and do not age well. Heat and cold (as well as dramatic changes between both) also don’t play well with glazed ceramics.

The result, so-called “craquelure”, is a fine web of cracks in the glaze which allow all kinds of liquids to seep into the body – from plain dishwater or tea/coffee to various forms of cooking spills including blood.