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I sometimes make alcoholic ginger beer and alcoholic lemonade. How would one estimate the abv of something like that? Is it even possible?

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Out of curiosity, what's your recipe for alcoholic lemonade? I've tried to dig up a good recipe and came up blank. –  Pulsehead Jul 15 '11 at 12:29
    
I couldent find anything good online so i made my own; I used 25 lemons (juiced) 500g sugar and 1.2kg Honey 5 tablespoons of artifical sweetener and water to top up to 10L. The yeast I used was champagne yeast. Turned out really nice but was a little too alcoholic, I might omit the sugar next time –  Tom Squires Jul 15 '11 at 12:30

1 Answer 1

up vote 7 down vote accepted

Yup, it can be easily measured using a hydrometer. Simply take a specific gravity reading before pitching yeast and after fermentation is complete. Find the difference between the two values, this will be proportional to the amount of sugar the yeast has converted to alcohol. Multiply this number by 131 and you get the ABV. For example:

You brew a ginger beer with original gravity (OG) of 1.09. After fermentation the final gravity (FG) is 1.01. The alcohol by volume is as follows:

ABV = (OG - FG)*131 = (1.09-1.01)*131 = .08*131 = 10.48%

Alternatively, if you don't have a hydrometer, you can make some educated guesses. If you know about how much sugar you are have, you can estimate the starting gravity using the specific gravity yield of the kind of sugar you are using.

I could go over the math for this, but if you want to make it easy on yourself, just use Beer Calculus. Just add your ingredients and it will estimate OG, FG, and ABV.

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