Excess Foam

February 12, 2006 12:40 AM

Why does beer foam more than usual when poured into a Styrofoam cup?

I'm a bartender, and I have plenty of experience pouring draft beer. I know that impurities inside a cold glass will cause foam to form, so I'm positing that the relative roughness of Styorfoam, as opposed to the smoothness of glass, causes the great amount of head I get when I pour beer into my throw-away, fuck-the-environment, politically-insensitive drinking device. Am I right?

posted by BitterOldPunk to food & drink (7 comments total)

I don't know if you're right, but this might account for it: soap, detergent, grease and wax residues actually attack the foam.

So maybe that's part of it? It's not that the styrofoam causes a larger head, it's that glasses may have a residue of detergent or soap, making the heads smaller.
posted by Windigo at 12:55 AM on February 12, 2006

I've found just the opposite, Windigo.

When there is noticeable soap residue on pint glasses, the beer tends to foam. In fact, you can see it forming on the glass at the spots where the residue remains. (I've actually run this demonstration to get our dishwashers to wash our bar glasses twice, to remove this soap scum.)
posted by BitterOldPunk at 1:00 AM on February 12, 2006

My home-brewing, chemistry graduate husband agrees that it's "most certainly" just the roughness of the styrofoam. He also thinks that glasses are usually colder, so the warmness of the styrofoam might have something to do with it too.
posted by web-goddess at 1:03 AM on February 12, 2006

Huh. And all this time I thought it was the other way around. I'm devastated. If I was wrong about this, what else am I wrong about?

However, I am still secure in the knowledge that it you rub your finger on your face, and touch the head of beer or soda, the foam will dissipate. So I have that, if nothing else.
posted by Windigo at 1:44 AM on February 12, 2006

I'm not sure that styrofoam is going to be any warmer. Most people don't store their glasses in the fridge, so they'll be at room temperature.

I suspect you think a glass is colder because it conducts heat away from your hand much more efficiently, your hand being warmer than room temperature and therefore the glass. However, the beer has probably been in the fridge and is colder than the glass, so it would gain heat from the glass much faster than it would gain heat from the styrofoam. To the beer, the glass probably 'feels warmer' than the styrofoam.

Anyway, I agree it'll be the roughness. It gives more nucleation points for the bubbles to form on. See this wiki link (on champagne rather than beer as it happens). I think the styrofoam surface will probably have large enough irregularities.
posted by edd at 2:38 AM on February 12, 2006

Actually I think he was referring to the glasses you get at pubs, but I guess that can vary quite a bit... Fair point, though, edd.
posted by web-goddess at 3:21 AM on February 12, 2006

I've never had beer out of styrofoam, but I know a few places that serve it in plastic cups, and haven't noticed extra head, so I think the roughness can be blamed more than the thermal properties.
posted by RobotHero at 8:59 AM on February 12, 2006