If you want a root beer float without the extra foam, take a page from the trusty bartender’s manual: Slightly tilt the mug or glass (about 20 degrees) while s-l-o-w-l-y pouring in the root beer.
Claudio Pellegrini, a professor of thermal and fluid sciences at the Federal University of São João del-Rei in Brazil, has calculated the optimal shape for a beer glass to keep the beer cold for ...