How much of a reading change is priming sugar going to make to FG

Discussion in 'General Brewing Discussions' started by Ward Chillington, Sep 20, 2020.

  1. Ward Chillington

    Ward Chillington Well-Known Member

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    So in my distraction of bottling and watching the final stage of the Tour de France; I didn't take an FG reading of my brown ale before I added my priming sugar. I have taken a reading with the priming sugar in the mix and it's not far off the mark from the expected FG by the recipe. What am I looking at folks?
     
  2. Bubba Wade

    Bubba Wade Well-Known Member

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    Assuming 5 oz of sugar per 5 gallons, the priming sugar would increase the specific gravity by about 0.0027. So, if you measured 1.009, your FG would have been around 1.006.
     
  3. Ward Chillington

    Ward Chillington Well-Known Member

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    Thanks Bubba...what's the calculation for that? .0027 points per gallon per once =.0027 = gallon / ounce or .0027 = ounce / gallon??? I was putting 3.5 ounces of corn sugar into 5.25 gallons of 68 ° beer to get 2 units of CO2
     
  4. Bubba Wade

    Bubba Wade Well-Known Member

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    That's the approximate equation and will work for low concentrations of sugar like we use for priming. At higher concentrations, it becomes nonlinear due to hydrogen bonding and such. So for your concentration, adjust by about 0.0018.
     
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  5. J A

    J A Well-Known Member

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    You can assume it generally raises the FG a couple of points in most beers for the purposes of making a reasonable estimate.
     
  6. Nosybear

    Nosybear Well-Known Member

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    According to the ABV calculator, if you add 2 points to prime, the alcohol content is increased 0.26%.
     
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  7. SabreSteve

    SabreSteve Well-Known Member

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    I made the same mistake when bottling the batch I have conditioning now. I just assumed there was going to be no way to get an accurate reading so I skipped the FG reading all together. Good to know for next time.
     
  8. Ward Chillington

    Ward Chillington Well-Known Member

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    OK...so lemme see if I got this .....27 or .26 percent increase so simple algebra says:

    ABV before priming * 1.0026 = ABV after priming so then we can change the equation to ABV before = ABV after / 1.0026

    My FG was 1.011 with the priming sugar in the beer and our handy dandy ABV tool on the site says my ABV is 5.12 with my OG at 1.050 so then ABV before = 5.12 / 1.0026 or 5.10 % ABV is the before priming figure. I'm assuming that since I'm not mixing my measurements and the algebra is all based on the percentage values, this sounds right to me....thoughts...corrections....calls for Ward to RDWHAHB??
     
  9. Nosybear

    Nosybear Well-Known Member

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    You're adding about 2 points of pure sugar to the beer. Before all the math, open the ABV calculator, put in your OG and FG and watch the ABV change. About 0.25%. And RDWHAHB.
     
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  10. Ward Chillington

    Ward Chillington Well-Known Member

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    Yeah...5 10...5.12 close enough, right?!
     
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  11. Nosybear

    Nosybear Well-Known Member

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    5.10-->5.102. About 0.25%.
     

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