glaze

In ceramics, a thin coating for pottery and porcelain, which gives the object a protective finish and helps to keep it from leaking and chipping. Glaze is applied by dipping a formed ceramic item into it or by painting onto the surface. It is fixed by firing in a kiln.

Different mineral glazes will react variously with the surface of the ceramic, according to the minerals present in the clay. Glazes may be alkaline, lead, leadless, tin, salt, or feldspathic. Glazed pottery is first known from the mid- to late-Neolithic period in Egypt, where glass was first made.