why does beer foam stay long in a layer on top of glass, and sodas or other bubbly drinks don’t have this kinda thing?
In: 9
Because beer contains a not-insignificant amount of protein which increases surface tension and allows the creation of the foamy head. Other carbonated drinks don’t have the protein so they don’t form the same kind of head.
It’s the same sort of reason why you can whip up egg whites and they get super foamy.
As a related aside, some beers aren’t carbonated they are *nitrogenated.* Since the ability of a gas to escape a liquid and enter the air is regulated by the amount of that gas already in the air, CO2 escapes readily (because there is only a small fraction of CO2 in air). Since the air is around 60% nitrogen it’s much harder for the gas to escape so the bubbles remain in the drink. This gives beers like Guinness their classic creaminess and allows them to stay bubbly, longer.
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