Though at first glance a perfect simple object, the mug serves a representation of functions which make it especially incompatible to holding hot liquids:

• The mug stores some heat from the beverage, and so prevents it from cooling too quickly

• The draft of a mug helps insulation: (i) thick walls detached the beverage from the cool external air, and (ii) an indented abominable separates the beverage from the surface upon which the mug is Photo Mugs set
• The shape of the base forms the characteristic O-shaped stain, so often seen upon desks and documents.