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 Home Brew Forums > apparent attenuation

07-16-2011, 10:50 AM   #1
aragornss
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 apparent attenuation

I all!

I read on "brew like a monk" the leffe blond specification:

Og: 1,064, Alcohol by volume: 6.6%, Apparent degree of Att. : 81%

But how is it possible? Usally I calculate the alcohol by volume in this way:

1, 064 - 1,013 (81% AA) --> 51 / 7.5 --> 6.8% that is different from 6.6%.

Is my formula wrong or is because I use the apparent attenuation and not the real?

Thanks!

Enrico

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07-16-2011, 01:33 PM   #2
MalFet
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Pretty much all math in brewing is based on apparent attenuation, though it is relatively easy to convert between apparent and actual.

The differences you are getting are just a result of when and where you are rounding your values. For example, 81% attenuation of 1.064 is not 1.013, but 1.01216. Your formulas are fine (though sometimes people use (OG-FG)/7.53), but they're just estimates, and even estimates are only as good as your accuracy/precision of measurement.

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