From the HBD Archive
From: pms@Sun.COM (Patrick Stirling (Sun USHQ Consulting Services))
Subject: Re: The Gravity of the Situation
Date: 1989-08-17 20:56:39 GMT

Papazian in 'The Complete Joy of Homebrewing' (which I recommend) has this
equation:
%age alcohol by waight = (SSG - FSG) * 105
Where SSG = starting Specific Gravity, FSG = Finishin SG.
To convert to volume, multiply by 1.25.

So for Mike's example of Budweiser (gag!) (1.045 - 1.005) * 105 * 1.25
gives 5.25% alcohol by volume, which is pretty close to the number given
in last Sunday's (8/13/89) This World section of the Ex/Chron. This also
bears out Doug's equation (which I didn't see, being a new subscriber).

On another topic, I have difficulty getting my wort to ferment out all
the way. I also find that the starting SG is lower than the recipe said
it would be. I don't have my records to hand but for one attempt at an
English style bitter, the recipe said it started around 1.060 and finished
around 1.016. I actually got 1.052 and 1.022 as far as I remember. Any
ideas on why the low initial reading and incomplete (presumably) fermentation?
This happens a lot (usually in fact). I use dried yeast, and it seems to
get started OK and there's plenty of activity. How critical is the
temparature?

patrick

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