Ceramic Mug

Ceramic is the material that made the mug the default vessel for a hot drink, and the reason is thermal: fired clay holds heat in its own mass and releases it slowly, so the drink stays warm for longer than the same volume in metal or glass. The glaze on top is a fused glass layer, which is why a ceramic mug takes coffee, tea and tomato soup without staining or holding a flavor from yesterday. Handle the rim carefully, since that is the thin edge where a chip starts, and a chipped rim is the one flaw that makes a mug unpleasant to drink from.