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Assuming full attenuation, is there a way to figure out what gravity reading would be suitable to not use priming sugar, and just allow the excess sugar to create the carbonation? A sub-question would be how much gravity some the 3/4 cup priming sugar add?

Example

The OG on my blonde was 1.052. I used California Ale Yeast (WLP001), which has an attenuation of 73-80%. Therefore, the potential TG is between 1.014 and 1.010.

If I bottle at, say, 1.016, will that be enough to carbonate the beer without adding sugar? 1.020?

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  • Note: the latest reading is 1.011, so I'll be adding sugar, but, I'm still curious.
    – hookedonwinter
    Apr 14, 2010 at 19:48
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    Excellent answer from Tetragrammaton. However, this is one of those "How can I do something far removed from best practice" questions. Too much guesswork. Predicted FG and real FG are two different things. The yeast, beer, and conditions for primary fermentation vary too much. Predicted FG, is just a target number, not a guarantee, no matter how careful you are. Even with Tera's excellent suggestion, you are going to get a huge amount of variability in the resulting carbonation. Bottle bombs and flat pints are going to be the norm, depending on the batch. Downvoted.
    – TinCoyote
    Apr 14, 2010 at 21:05
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    So with that much variability, how does one know to use 3/4 cup priming sugar?
    – hookedonwinter
    Apr 14, 2010 at 21:25
  • PJ the variability isn't from carbonating completely with a known amount of sugar (whether added or residual from the ferment) but the variablity that comes from trying to time you ferment just right that you don't have to much or too little. Calculating the proper gravity at which to bottle is fairly simple. But not many of us are able to be on hand with our beers 24 hours a day. Say the proper gravity is 1.018. Before work you test the gravity and its 1.022, you come home from work and its now 1.015.... you missed it. Probrewers that do this have much tighter/familiar ferments than us.
    – brewchez
    Apr 15, 2010 at 15:20
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    So you're saying the solution is to quit my job and go pro? Done.
    – hookedonwinter
    Apr 16, 2010 at 14:50

1 Answer 1

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You know that your mean potential FG is 1.012 (this is an example, when designing your batch you can predict your FG more or less). You can find the amount of priming sugar needed according to style and temperature from here: http://kotmf.com/tools/prime.php

Now that you know the amount of priming sugar needed, all you have to do is the following:

OG needed=FG+(priming sugar*sugar gravity)/(volume)

All you have to do is insert the values of FG (predicted), amount of priming sugar needed, sugar SG per gallon and your volume in gallons and you've got the requested gravity!

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