# Why does the second beer in a glass foam less than the first one?
**URL:** https://boards.straightdope.com/t/why-does-the-second-beer-in-a-glass-foam-less-than-the-first-one/322399
**Category:** Factual Questions
**Created:** [September 19, 2005, 6:23pm UTC](https://boards.straightdope.com/t/why-does-the-second-beer-in-a-glass-foam-less-than-the-first-one/322399 "2005-09-19T18:23:28Z")
**Posts on this page:** 11
**Page:** 1
### Author:  [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)
#### Post date: [September 19, 2005, 6:23pm UTC](https://boards.straightdope.com/t/why-does-the-second-beer-in-a-glass-foam-less-than-the-first-one/322399/1 "2005-09-19T18:23:28Z")
This is an experiment that I have done thousands of time with the same result. You can open a can of beer, pour it into a glass or a plastic cup, and it will foam a lot. You won’t even be able to drink it very well for a couple of minutes. Now take same glass or cup and pour another can of beer into it. It won’t foam nearly as much. The foam will be less high and it will go away much faster. I belive this also happens with beer from a tap.
Why is that?
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### Author:  [@Giles](https://boards.straightdope.com/u/Giles)
#### Post date: [September 19, 2005, 6:31pm UTC](https://boards.straightdope.com/t/why-does-the-second-beer-in-a-glass-foam-less-than-the-first-one/322399/2 "2005-09-19T18:31:09Z")
I’m assumng that you emptied the glass before the second pouring by drinking from it. When that happened, oils from the skin around your mouth got on the glass, and those oils inhibit beer foaming.
(Try this experiment, which I haven’t tried, but which I predict the results of. Take two identical glasses, and put a tiny amount of oil in one, e.g., by dipping your finger in cooking oil, wiping most of the oil off your finger, then tuching the inside of the glass with your finger. Then pour beer into both glasses. I predict that the glass with oil will foam considerably less.)
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### Author:  [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)
#### Post date: [September 19, 2005, 6:56pm UTC](https://boards.straightdope.com/t/why-does-the-second-beer-in-a-glass-foam-less-than-the-first-one/322399/3 "2005-09-19T18:56:31Z")
[QUOTE=Giles]
I’m assumng that you emptied the glass before the second pouring by drinking from it. When that happened, oils from the skin around your mouth got on the glass, and those oils inhibit beer foaming. QUOTE]
I am talking about an emptied glass. That is a pretty good guess although I have never thought of myself as Crisco lips.
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### Author:  [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)
#### Post date: [September 19, 2005, 7:01pm UTC](https://boards.straightdope.com/t/why-does-the-second-beer-in-a-glass-foam-less-than-the-first-one/322399/4 "2005-09-19T19:01:50Z")
Might it not simply be that the glass was _wet_ the second time? Bubble formation is helped by nucleation sites, and a dry glass or cup with lots of dry irregular (on a microscopic scale) sites would provide ideal nucleation points. (You wanna see this effect dramatically? Dump salt into a beer or soda, as in Robert Altman’s film **Three Women**. The salt grains have _[lots_ of nucleation sites)
An easier experiment (which doesn’t result in oily beer) would be to fill a glass with water, then dump it out, then fill with beer, and compare to a similar glass or cup filled dry.
I kinda doubt a little grease from lips would inhibit foam in an entire cup.
> [@](#):
>
> This is an experiment that I have done thousands of time with the same result.
Well, experimentation is most of the fun. Try my experiment several times. With many different varieties of beer. Report back when you’re able.
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### Author:  [@sqweels](https://boards.straightdope.com/u/sqweels)
#### Post date: [September 19, 2005, 7:03pm UTC](https://boards.straightdope.com/t/why-does-the-second-beer-in-a-glass-foam-less-than-the-first-one/322399/5 "2005-09-19T19:03:22Z")
My WAG would be that there’s carbon dioxide left in the glass from the previous beer. Beer bottlers put a puff of CO2 in the bottles before filling them to prevent foaming.
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### Author:  [@crazyjoe](https://boards.straightdope.com/u/crazyjoe)
#### Post date: [September 19, 2005, 7:09pm UTC](https://boards.straightdope.com/t/why-does-the-second-beer-in-a-glass-foam-less-than-the-first-one/322399/6 "2005-09-19T19:09:12Z")
I used to see this all the time when I workled in a restaurant, and my guess is that **CalMeacham** is correct. When the 'tender poured beer into a glass fresh from the dishwashers (ie still damp) it resulted in a lot less foam then those which were dry.
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### Author:  [@crazyjoe](https://boards.straightdope.com/u/crazyjoe)
#### Post date: [September 19, 2005, 7:10pm UTC](https://boards.straightdope.com/t/why-does-the-second-beer-in-a-glass-foam-less-than-the-first-one/322399/7 "2005-09-19T19:10:47Z")
**than** those which were dry. {sigh}
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### Author:  [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)
#### Post date: [September 19, 2005, 7:12pm UTC](https://boards.straightdope.com/t/why-does-the-second-beer-in-a-glass-foam-less-than-the-first-one/322399/8 "2005-09-19T19:12:01Z")
> [@sqweels](#):
>
> My WAG would be that there’s carbon dioxide left in the glass from the previous beer. Beer bottlers put a puff of CO2 in the bottles before filling them to prevent foaming.
Um, no, they put CO2 in the bottles to _make_ them foam… if they didn’t, it’d be flat.
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### Author:  [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)
#### Post date: [September 20, 2005, 12:55pm UTC](https://boards.straightdope.com/t/why-does-the-second-beer-in-a-glass-foam-less-than-the-first-one/322399/9 "2005-09-20T12:55:23Z")
I experimented with dumping various things into soda last night and watching it fizz over – salt does it, sugar. Even sand. MilliCal was much amused. Pepper Mill suggested baking soda, but it was getting too late – maybe we’ll do that tonight.
Haven’t tried the “wet-down-the-glass-and-compare-foam” though, especially with beer (I hate beer). Someone else will have to throw themselves on that grenade.
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### Author:  [@El\_Zagna](https://boards.straightdope.com/u/El_Zagna)
#### Post date: [September 20, 2005, 1:20pm UTC](https://boards.straightdope.com/t/why-does-the-second-beer-in-a-glass-foam-less-than-the-first-one/322399/10 "2005-09-20T13:20:02Z")
I’ve noticed the same thing with champaign. (I don’t mean to suggest that I’m a classier drinker than **Shagnasty** , it’s just that I drink my beer straight out of the can. Drinking champaign straight out of the bottle causes it to foam up inside your mouth and spew out your nose. I know this from experience.)
Wetting the inside of the glass with water reduces the foaming as well as wetting it with beer or champaign. It’s the wetting that matters.
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### Author:  [@chaoticbear](https://boards.straightdope.com/u/chaoticbear)
#### Post date: [September 20, 2005, 1:35pm UTC](https://boards.straightdope.com/t/why-does-the-second-beer-in-a-glass-foam-less-than-the-first-one/322399/11 "2005-09-20T13:35:12Z")
> [@Ethilrist](#):
>
> Um, no, they put CO2 in the bottles to _make_ them foam… if they didn’t, it’d be flat.
I believe that he’s talking about extra CO2, that way, there’s more pressure above the beer, which would help keep more of the CO2 in the beer via the equilibrium etc stuff.