Joe Sixpack

Joe Sixpack: Beer primer: 16 things to know about foam

W E DON'T pay much attention to bubbles in our beer, unless they're foaming over the coffee table.

When it comes to beer pleasure, though, bubbles are right up there with color, aroma, flavor, body and buzz. So, with the help of West Chester University chemistry professor Roger Barth, Ph.D., author of The Chemistry of Beer (Owl's Nest Publishing); Marty Nachel, whose second edition of Beer for Dummies (Wiley) was just released; and the draft beer gurus at Anheuser-Busch, here are 16 things to know about foam.

1. Foam is the expansion of pressurized carbon dioxide that is created during yeast fermentation. Upon opening a bottle, the pressure drops, bubbles of expanding gas form then burst, allowing dissolved gas molecules to escape the liquid.

2. Zzzzzz . . .

3. Wake up, or it's going to gush all over your coffee table! This phenomenon is not uncommon in homebrews, where bacterial contamination creates excessive bubble nuclei that expand uncontrollably.