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I have this great mulberry syrup I found. I want to prime with it, and I forget how to figure this out with an unknown sugar source. I see that John Palmer's "How to Brew" references measuring the gravity of honey (a variable ingredient) to figure out priming rates in How to Brew, but he mentions you could dilute it and measure it with your hydrometer.

So, say you have some awesome backyard beekeeper's honey or other lovely sticky stuff you want to dilute into a priming liquid. What steps do you take, and what's your math to figure out how to get, say, 2.5 volumes of CO2 into a 3 gallon batch of beer? Or even a 5 gallon batch.

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Why bother running the risk of messing up the priming calculation and ruining a batch based on the chance of adding a tiny bit of extra flavor? Just add some of that syrup to the primary, let it ferment out completely, then prime & bottle as normal. –  Graham Feb 27 at 13:35
    
@Graham - I don't know if it is true, but on HB forums many advise adding honey in the secondary vessel or at priming to retain at least some honey flavor and aroma. If that is good info, would not the same thing be true for mulberry syrup, or other syrups? –  Chino Brews Feb 27 at 20:29
    
@Chino, I've made a honey ale twice now, which has 3lbs of honey added to the primary after primary fermentation stops. That process works great, and should theoretically work for other nicely flavored syrups besides honey. –  Graham Feb 28 at 14:04
    
Thanks for the perspective. I have also racked off a gallon onto an interesting dried fruit while bottling the rest, so using syrups in that way is another possibility. I've enjoyed ciders primed with fresh apple juice, and I once made a pineapple pLambic with pineapple at each stage including fresh squeezed juice to prime -- actually, under-prime. I do think there is a place for characterful priming. –  Gail Williams Mar 11 at 16:58
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1 Answer

up vote 5 down vote accepted

If you follow a process like this, you won't be far off:

  1. Dilute the syrup to create a 10% solution. E.g. add 10g of syrup to 90g of water and stir well.
  2. Take the specific gravity of the 10% solution, e.g. 1.030
  3. Express this as a fraction of a 10% solution of sucrose, which has specific gravity 1.040. So, our example of 1.030 is .75 the gravity of a 10% sucrose solution.
  4. Use a priming sugar calculator to determine how much sucrose to prime with. E.g 100g.
  5. Divide this number by the fraction derived in 3. E.g 100g/.75 = 133g. This is how much of the undiluted syrup you need for priming.

Please note that this only an approximation because we're not accounting for the increase in volume from the added priming syrup. If the syrup is very sweet (like honey), the effect of the additional volume is negligible. If it's not particularly sweet (like fruit juice, e.g.) then the effect is large.

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