Message 15381 of 39188 in General Discussion

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> Following the theory, you can choose to say the ice crystals form a 
> lot more points of .. um ... effervescence.
> http://dictionary.reference.com/search?r=2&q=effervescence
> hence foam more. OTOH a mildly chilled class may melt the 
> condensation almost immediately (between the chiller and the tap) and 
> 'wet' the glass for a smooth pour. Wild-assed-guesses all the way 
> here.
> 
> vuo-fin ? Darcy/doneil ? (some of our mixology chemists)
> 
> Strangely, I noticed/thought of this when serving a champagne 
> tonight. I actually had to wash the glass (no glassware, lipstick) 
> and avoided drying inside. -> A near-full glass of champers in one 
> pour. 

Basically, what's happening is that the surface of a dry glass is actually 
rough on a microscopic scale. This provides a surface point where a bubble can 
form. The best way to think of it is that 'rock candy' experiment we all did 
in grade school. i.e. you make a super concentrated solution of sugar water 
and then put a string in it and the crystals grow. The string has many more 
points for the sugar to grow on than the glass. 

Anyway, water has surface tension which forms a smooth barrier between the 
glass and the beer. Think of it as lubricant. The beer pours down the 
lubricated surface and the number of CO2 bubbles is reduced. 

Also, depending on you establishment, the cleanliness of the glass plays a 
huge part. Even slightly dirty glasses will produce a lot more foam. A 
perfectly clean and dry glass made of good glass should not foam that much. 
Think champagne crystal, it does actually play a role in great champagne, they 
just don't sell them to be elite.

Darcy