Priming Calculator Temps

[nfeuerhelm]

I've been getting back into brewing this year. While working through some different tools figuring out what works for me, I noticed an oddity with priming sugar calculators, that they all use different temps for the calculation.

• Norther Brewer's Priming Sugar Calculator - uses current beer temp
• BIABacus - uses target fermentation temp
• BrewFather - uses peak fermentation temp
• How to Brew - appears to use current temp but doesn't say specifically

I brewed 1 gal of Kolsch style beer with the following steps: ferment at 64f, diacetyl rest at 68f, then cold crash/age to 40f, and it ended up at about 50f after letting it sit before siphoning to the bottling bucket. The calculators give me these weights of dextrose for 2.7vols CO2:

• NB - 23.57g
• BIABacus - 24g
• BrewFather - 30.05g
• How to Brew - 0.72oz/20.4g

I ended up using the BIABacus number for this one and it turned out fine, but now I am curious how close it actually came to my target 2.7vols CO2. There is an ~10g range here for what should be the same result, right? What is the right way to calculate this and/or what is the most accurate calculator? Out of curiosity, does anyone know why conditioning temp or serving temp don't factor in to this?

Thanks!

 

[nfeuerhelm]

So the "Similar threads" thing at the bottom does a better job searching for threads than I did.

The best I have been able to find is that the correct temp to use is the highest temp after active fermentation has stopped but before bottling. Is this correct and if so, which calculators work properly using this temp?

It seems this temp is used to determine how much CO2 is already in solution. I have been using a Cold Crash Guardian more recently. The check valve on this is supposed to open at about 0.5psi. This isn't enough pressure to effect the calculators, correct?

 

[Stormcrow]

Your second to last paragraph sounds spot on to me. The beer releases co2 as the temperature climbs, and with a fermenter that is only under airlock pressure, not much can dissolve back into the liquid from the headspace when cold crashing. The chart i always use for priming is the one found in Palmer's How to Brew. I'm not sure which edition I have, but i keep a bookmark on that page. It's always worked like a charm for me.