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Is this a viable method?: In theory you can calculate an estimated ABV by using the formula 17*X%*YL. This means that 17 gr sugar produces 1% alc. in 1 liter mash. So if you know at what alc.% your yeast gives in and how many liters mash you make you can derive how much sugar you should add to reach there.

To know for sure when all sugar is consumed by the yeast, using a hydrometer and the formula that 2,7 gram sugar is 1° Oechsle in 1 liter mash, you would be able to know when all sugar is gone.

If you keep track of consumed sugar on the hydrometer scale, and when it finishes bubbling as predicted - would you be able to verify the ABV with a refractomer measuring plain % alcohol??

  • I think where you'd run into trouble here would be knowing the % that your yeast gives in. Correct me if I'm wrong but doesn't it depend on the sugar volume in the wort? So there isn't an exact % rather how much it's going to work with the sugar available (ie. attenuation). – fitzy101 Apr 15 '15 at 10:19
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Yes and no (sorry).

It depends on the kind of sugar used, as well as the yeast. You could get close with grapes or honey, as nearly all the sugar will ferment. But malt/malt extract would always have a good amount of unfermentable sugar in it, adding uncertainty in addition to the yeast.

Now, if you know your yeast and your fermentables very well, then yes you can do this in a way. Every good brewer or beer recipe will predict the resulting alcohol, based on some version of the above formula.

As far as checking finished product with a refractometer, see this link.

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It's far easier to use (OG-FG)*.132

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