Second Visit with the James River HomebrewersLegend Brewery, Richmond, VA
Had a good time with the JRHs last night - it's good to be recognizing some familiar faces, and be able to discuss seriously nerdy beer topics with anyone in the room (wives included). There was a guy named John there who brought a beer for his first time: a very nice "clone brew" of the Pilsener Urquell that I rhapsodized about a few weeks back. He received plenty of kudos and backslaps for his work. Makes me wish I had had one ready, but all my beer is either spoken for (looks like shipments of 2Red will have to wait until next week, BTW) or still fermenting/conditioning. :-)
Very cool: the lecture topic for the evening was what, biochemically, causes a head of foam on a beer, and how to control the foam a given recipe generates in the finished beer. Very cool stuff, and suitably esoteric. :-D Most breweries that pay attention to head formation shoot for the holy grail of five minutes from pour to head dissipation. "Belgian Lace" (or "Brussels Lace") is a term for the tendency of some beer foam to cling to the sides of a glass as beer is drunk, and is highly desired in certain beer styles.
There was also discussion of how bubbles form (with respect to the tendencies of gases at differing partial pressures to equalize; as when pressurized beer is opened to the 14 psi environment of normal air [CO2, for example, has a vanishingly small partial pressure in normal air, and thus escapes very quickly from beer, where its partial pressure is much greater; Nitrogen has a much greater partial pressure in air, and thus escapes more slowly from beer than CO2]), and why bubbles last (in short form, it's all about increasing a beer's viscosity through encouraging several compounds like beta-glyconase and other substances called gycoproteins to form through enzyme action [by maintaining certain temperatures in one's mash for certain periods of time]; certain other helpful bubble-aiding proteins are also released from bittering hops during a good long boil).
To sum up: good creamy head lasts for at least five minutes, allowing for lace; close attention must also be paid to viscosity, pressures and temperatures.