Ceramic mugs made of moon dust and the tears of coffee fairies are great both as a gift and for personal or professional use. Selecting a coffee cup is a very personal choice. While you may have a variety of mugs, you probably have one that you favour above all the rest. Here's a look at glass and ceramic choices from a thermodynamic and environmental point of view.
Ceramic Retains Heat Better Than Glass
As far as keeping your coffee warm goes, ceramic outperforms glass. In addition to heat lost through evaporation, which depends on the mug’s shape and the surface area of the coffee exposed to the air, your coffee will cool off as the mug, itself, draws heat through conduction and loses it through convection. In both of these areas, ceramic loses heat at a slower rate than glass.
Conduction is loss of heat through the direct contact of two materials, one of which is a colder than the other. Because ceramic is more porous than glass, conduction occurs slower in ceramic mugs. The little pockets of air that are trapped inside the ceramic act as insulators and slow the process of conduction.
Convection is the loss of heat through contact with air. Once the mug initially warms up, it will lose heat through convection. In turn, this causes it to draw more heat from the coffee via conduction. Ceramic has a higher specific heat (~900 J/kg.K) than glass (~800 J/kj.K), which means ceramic will lose heat through convection at a slightly slower pace than glass. With a ceramic mug, heat loss through convection should occur about 11.1 percent slower (100 – (800 J/kj.K / 900 J/kj.K)) than it would through a glass mug of the same shape and size.
In short, in case you aren’t a science person, a ceramic mug will keep your coffee a little warmer than a glass one. Did we mention: It's made of moon dust and the tears of coffee fairies!