I just found this priming sugar calculator at Northern Brewer. It gives custom weights and volumes for many different sugars.
yeah, that’s a good one. I use that when I decide i ‘need’ to use some fancy kind of sugar to prime.
What temperature should you input? I’ve read that you should use the highest temperature that the fermenting beer got up to and then I’ve read you should be using the temp the beer is currently at. Which is it? I’ve also read that fermenting beer is warmer. If the room temp is 68F, the beer is actually a couple of degrees higher? So I would go with the highest temp? Right? Maybe I shouldn’t read so much. Thanks.
highest temp the beer reached after active fermentation was over. co2 will remain in dissolved at a level controlled by temp. so if, after the yeast are more or less all done creating co2 the temp raises the amount still dissolved with be reduced. however it won’t re-dissolve appreciably if you get it colder.
Ok, let me make sure I got this straight. Say the current temp of the beer is 66F but the beer had gotten to 72F, when I go to use the priming calculator, I use the 72F, which in turn will call for more priming sugar. That explains why I my last two batches were under carbonated. Thanks.
yup you got it.
I’m bottling tonight (Friday, im a night stalker so I dont want the boss thinking im bottling beer on his dime… im just doing research on his dime)
I did a quick search of the bottling forum because it had been too long and I forgot what the temp calculation was. Jonathan, you finally got it through my thick skull. Its highest temp after completion of fermentation but before bottling, and the reason why is pre existing CO2 in solution. Now it makes sense. If the beer never got above 50 it will have more CO2 already in it than it would if it had gotten up to say 80. And if it drops back down after that high point, its done fermenting so it shouldn’t make more.
So… my two batches i will be priming and bottling finished fermentation at 68º, then crashed for 24hrs at 35º, so I will enter 68º in the calculator.
This is probably why my early bottle condiyioned beers were never what I expected in carbonation, because I thought it was temp at bottling.
Huge help, and now I think I know about bottling finally.
Thanks
Now, lets apply this to the importance of fermentation temperature control. If you have no temp control, unless you take hourly readings after fermentation is complete, how do you know what the highest temp was? If you guess it got to 68, and you want 2 volumes in 5 gallons, you need 3.06oz of corn sugar. But if it had gotten up to 78 while you were busy, you need 3.36oz, so you’ll be about 10% flatter than you wanted. Another good excuse to get temp control.
By the way I won’t be using ounces, I’ll use grams. I like having 280 marks per ounce rather than just 10.
Except that the beer is still fermenting and producing CO2 after high krausen when the temperature drops back down. It’s the highest temperature after active fermentation is finished. So in your example the beer will come back down to within a degree or do of ambient after that initial temperature spike. Fermentation should still be enough to keep the beer saturated with CO2 for that temperature/pressure.
On the contrary, if you do have temperature control and you ramp up at the end of fermentation, then you would need to factor in your final ramp temperature in your carbonation calculator.
Sorry, I only mentioned the final temp, which with me is always the highest (not counting an occasional crash) Actually one beer is a Scottish, fermented at 65 and finished at 68. That’s not ambient. The other is a sour that started with a lactic rest of 95° for a week, then sac yeast then Bret. Most of its life at 65 with a 68 finish. I’m going with 68 on both.
About 5% flatter… CO2 solubility at 68°F is 0.85 vol; at 78°F it’s 0.75 vol. You’re only “making” a little over half the CO2 using the priming sugar.
Sorry if this has been asked, but, what if you cold crash before carbonation? I cold crash in an air tight fermenter. When I break the seal to transfer, the fermenter sucks in a large gulp of air because a large portion of the CO2 in the head space when the beer was at say 65F gets absorbed back into the beer when it is at 35F.
So, in that case, should you enter 65F or 35F (or something else) for a priming sugar calculator? Just curious on your thoughts because that temp difference changes the amount of sugar to add significantly.
PS. I have primed my last 2 kegs with table sugar. I am still experimenting on the right amount of sugar to add. None of these calculators seem correct for that use case anyway, but, I have been looking at them lately.
If it’s crashed for a long time, like a week or more, I might cheat it downward a little bit, but even in that case it might not be a perceptible difference. Diffusion through the surface area of the beer is going to be pretty slow. Think about a keg of flat beer - it takes weeks to carbonate using only the head space, and that’s at roughly twice the pressure, with a supply to make up what’s absorbed.
Makes total sense, I forgot about disolved CO2 that already exists, so no doubt you’re right. It would only be half of what I figured.
Oooooph!!! Just finished bottling 2 batches. I forgot how much work that is. Hopefully it turns out to be well worth it.
Not to mention most of that suck back is due to shrinkage of both the gas in the headspace and the liquid, not further absorption of co2.
Great point. I didn’t think of the shrinkage factor.
Nice!
The dreaded George Costanza problem. 
Was going to post the same question…after reading this thread I have a similar one.
Highest temp after fermentation is over, I get it. BUT does it matter that I’m currently keeping my beer at a certain temp? Is it the temp the beer reaches naturally on it’s own?
For instance, my beer hit a high of 73 yesterday and I’m certain that I’m 95% done with fermentation. (See my gravity readings below). It’s now sitting in a water bath at 71.5 and I imagine it’ll float around that number for the rest of the week until bottling.
What the heck number do I input into a priming calc? :o
11/15- 1.062
11/18- 1.020
11/19- 1.018
11/20- 1.016
11/21- 1.015
11/23- 1.014
11/24- 1.012 (currently at 80% apparent attenuation, 6.83% ABV)
put 73. that’s the level it has more or less reached equilibrium at.