Saturday, May 16, 2009

I love the fizz of a good cask ale

The Washington DC City Paper recently ran a very favorable review of a cask ale event at an Arlington, Virginia pub.

My ongoing love affair with cask beer led me to this special sampling of Clipper City’s IPA, poured straight from the firkin. Falling directly from quarter-barrel spigot to glass, like Gatorade from God’s own sideline cooler, this fresh IPA swaps its piney bitterness for more rounded, floral hop flavors. Waves of bagel malts roll across the palate, prodded along by the cask’s wondrous not-quite flatness. Uncarbonated beer? Damn right, and it’s firkin time you try it.

The Beerspotter
Ales: Not just for pirates.
By Orr Shtuhl
Posted: May 6, 2009

I responded: well, not quite. Cask ale should never be "uncarbonated." If it were, it would be an unrefreshing pint.

A well conditioned cask ale should contain about 1.0 - 1.4 volumes of carbonation, that is, naturally-produced carbon dioxide (CO2).

As a comparison, draught and bottled beer (whether it's mainstream light beer of fuller-flavored 'craft beer) contain 2.5 (and greater) volumes of CO2. That's more an indication of over-carbonation on their part —approaching gassy soda pop levels—than under-carbonation on cask ale's part.

Look at a well-conditioned cask ale in the glass just after it's been pulled through a handpump or poured directly from a cask. You'll see an upward-cascading curtain of bubbles slowly coalescing into a thick collar of foam. That is indeed carbonation —natural carbonation— formed within the cask by actively fermenting yeast.

You may have heard that complaint that "beer is bloating?" Not so with cask ale. It's neither over —or under— carbonated. It's refreshingly just right.

Firkin Brown Ale: Capitol City Brewing, May 2009
Nut Brown Ale pulled from a firkin at
Capitol City Brewing Company, Arlington, Virginia. 2009.05.15

What's a CO2 volume?
  • A volume of CO2 is the amount of CO2 that has the given volume at a standard temperature (32 °F) and pressure (1 atmosphere at sea level, or about 14.9 pounds per square inch).
  • Thus, a bottle of beer that contains 2.5 volumes of CO2 would contain the equivalent of two and one-half bottles of CO2, compressed into the space of that one beer bottle.
  • One mole (remember your high school physics and Avogadro's number?) of CO2 at 32 °F and one atmosphere will weigh approximately 44 grams and measure 22 liters.
  • Thus, 2 volumes of CO2 in a 12 fluid ounce bottle of beer would be the equivalent of 1.3 grams of CO2.
  • 2.5 volumes of CO2 in a 12 fluid ounce bottle of beer would be approximately 5 grams of CO2 per liter. And so on.
More truth to cask:

No comments:

Post a Comment

Comment here ...