Message 5743 of 22774 in Behind the Bar

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> Hi Dan the Melon Man,
> I followed your link till
> "Why when pouring into a wet glass, do sparkling wine or beer not 
> froth up?"
> that should give me the answer. However, it brings me to an 
> unappropriate site titled with "In the pink". It must be the web 
> site's error.
> I haven't reached the destination.

Bubbles in liquid don't arise spontaneausly. Imagine blowing up a balloon. The 
first part is the hardest. A small blown up balloon has more pressure in it 
than a large blown up balloon. Before the dissolved gas in beer can form 
stable normal sized bubbles it would have to pass the first step of an 
unstable very small bubble. But small bubbles are very improbable in beer as 
their pressure is such high that they dissolve back into the beer. Problem: 
gass bubles will not form.
But, in your beer glass is dust. This dust acts as a nucleation site. A place 
where bubbles can form without the need of the improbable first step of very 
tiny (sphere) bubbles with very high pressures. The glass itself is also a 
nucleation site for bubbles to form. Look at a glass filled with carbonated 
beverage and see the bubbles forming at the surface of the glass. Bubbles can 
also arise as one shakes. 

Wetting the beerglass is to control the foam formation preventing too much 
formation of bubbles. It cleans the glass of dust particles and changes the 
glass surface. Pilsner beers are supposed to be poured in wet glasses to 
maintain as much dissolved carbondioxide. Some beers don't need this and some 
are even supposed to be poured in a dry glass.

Wetting the beerglass also makes it possible to check the glass being clean. 
If you look at the water film against the surface of the glass it should cover 
the whole surface without leaving any dry places. Those dry places are fats on 
the glass and fats make the foam less stable.

There is a lot more information about beer bubbles on the internet. You can 
start with google.