15

I've seen people wipe the area around their nose then touch the foam/head on their beer after a bad pour.

Does this make the foam go away faster?

Sklivvz
  • 78,578
  • 29
  • 321
  • 428
dting
  • 395
  • 2
  • 8
  • 1
    Good question. Heck, I have even done this! A related question may be about putting a dash of salt on the foam. Anyone else ever heard of, or seen, this? – JasonR Apr 20 '11 at 20:29
  • 3
    This really does call for an experiment. – Jivlain Apr 21 '11 at 01:00
  • 1
    I volunteer to be the beer drinker! @Brightblades, yes, I have heard about the pinch of salt, although it may have been in regards to the taste of poor quality beers instead of the foam. Not sure. – Larian LeQuella Apr 21 '11 at 01:15

1 Answers1

12

Inserting your finger into any foam will disrupt the bubbles and cause them to come into contact with a separate surface than just the surrounding bubbles. This agitation serves to break bubbles. The addition of oils actually has a basis in fact because of the chemical nature of beer bubbles. This webpage explains

Each molecule of these grain proteins have two ends with different chemical properties; one end is attracted to water, while the other is repelled by water.

As gas bubbles emerge from the beer, nearby protein molecules rearrange themselves with their water-avoiding ends sticking into the gas bubble, away from the liquid. At the same time, the water-loving ends stick out into the beer.

Each bubble of gas is surrounded by a layer of protein molecules which are all lined up in the same direction, strengthening the surface of the bubble.

Oils from your skin stop the foam from overflowing by breaking up the protein layer surrounding each gas bubble. As the water-avoiding ends of the proteins are more strongly attracted to the oil than to the gas they pull out the bubble, weaken its surface, and cause it to pop.

This web page provides an experimental set up you can perform on beer foam. One of the conclusions/discussions says

Soap, detergent, grease and wax residues will kill foam formation and retention actually attack the foam on a head of beer. Fatty substances are attached to the surface on the bubbles. The surface tension on the bubbles is lowered. They will burst. As a result the foamy head disappears, causing the beer to look and taste "flat".

While not totally relevant, it is none the less interesting, scientists have performed mathematical studies of beer bubbles (and who wouldn't want to assist in that research?). As one of the most common beverages, we do spend a lot of time studying it. A subject I endorse.

Community
  • 1
Larian LeQuella
  • 44,977
  • 18
  • 187
  • 208
  • 3
    And again I learned something new. I was convinced that this would have been an urban legend with no basis in actual chemistry or fact. I thought it would be related to the soda can tapping "trick" that was asked earlier. Love it when I learn stuff! – Larian LeQuella Apr 23 '11 at 15:58
  • As an avid home brewer, it's curious to me that anyone would question this. But then again I suppose I spend more time with a pint at my lips than most. Oils from makeup or poorly washed glasses will most definitely destroy the head on a beer, which is a real shame if it's a good beer with a good pour. – Graham Aug 31 '11 at 12:33