Saturday, February 25, 2012

Awesomeness by Volume

Alcohol by volume (which is abbreviated as abv, ABV, or alc/vol) is a standard unit of measurement for determining how much alcohol (or ethanol) is contained in an alcoholic beverage. It is expressed as a percentage of total volume and is used worldwide.

In some countries (mostly French speaking ones), alcohol by volume is referred to as degrees Gay-Lussac, which is named after the French chemist Joseph Louis Gay-Lussac.

In beer, ABV levels range between 2% and 12%, and are usually between 4% and 6%. By comparison, malt liquor is 5%+, barley wine (or strong ales) ranges from 8% to 15%, wine ranges from 9% to 16%, vodka ranges from 35% to 50% and rum ranges from 37.5% to 80%.

A standard-issue hydrometer is used to
measure specific gravity in beer
After the sugary wort (or young beer) is boiled, yeast is added, which begins the process of fermentation. During fermentation, the yeast organisms consume the sugars and produce alcohol. Because the density (or specific gravity) of sugar in water is greater than the density of alcohol in water, it is possible to measure (with a hydrometer) the change in density in order to calculate the volume of alcohol in the solution.

The formula to figure out ABV in beer is: ABV = ((1.05 x (Original Specific Gravity (OG) – Final Specific Gravity (FG))) / Final Specific Gravity (FG) / 0.79 x 100, where 1.05 is the number of grams of ethanol produced for every gram of CO2 produced and .79 is the density of ethanol. An alternative formula that is used by many brewers is: ABV = (OG - FG) x 131.

It’s important to realize that, contrary to popular belief, high specific gravity does not necessarily equal high ABV. The ABV is determined by the difference between the original specific gravity and the final specific gravity.

Here’s to craft-brewed happiness… Cheers!!!

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