Priming calculation when adding CO2 during cold crash

[Adra]

I noticed that my beers are overcarbonated. when adding priming sugar i use the calculators and input the highest temperature of my beer after fermentation ended. since i noticed that my beers where more carbonated then they should i started looking for possible causes. I noticed the temperature that the calculators need is a heavily discussed topic, but clear to me. after fermentation ends the beers no longer creates co2 so the highest temp is the temp u use in calculating priming sugar BUT when cold crashing i add co2 to my fermenter to keep positive pressure and avoid suckback. so during my complete fermentation process (including cold crash) i always have 100% co2 in the headspace at normal atmospheric pressure. so.... if i ferment at 70, cold crash at 32 and condition at 65. what temp should i use in the calculators when adding co2 during cold crash

 

[mac_1103]

if i ferment at 70, cold crash at 32 and condition at 65. what temp should i use in the calculators when adding co2 during cold crash

The amount of additional CO2 dissolved in your beer depends on time as well temperature and pressure. So how long are you cold crashing? Unless you crash long enough for the system to reach equilibrium (i.e, >2 weeks), using the crash temp in a priming calculator will lead to undercarbonation.

You might find this discussion interesting.

 

[Bobby_M]

I don't think this can be accurately calculated. It is true that CO2 present during cold crash will raise the volumes of CO2 in the beer but it wouldn't be the same as if you put 32F into the calculator. I would either stop cold crashing or experiment with the calculator by stepping down the "max temp" figure by 10F until you get it approximately right to your taste.

 

[Adra]

The amount of additional CO2 dissolved in your beer depends on time as well temperature and pressure. So how long are you cold crashing? Unless you crash long enough for the system to reach equilibrium (i.e, >2 weeks), using the crash temp in a priming calculator will lead to undercarbonation.

You might find this discussion interest

I cold crash for anywhere between 2 to 5 days at about 0-2psi (i use the SS brewtech chronical fermenter with the pressure release at 2-2,5psi).
since my beers are all over carbonated and i always go to the lower end of the priming sugar calculator this seemed like a likely culprit. i am not a fan of highly carbonated beers so if i have a style that should be carbonated between 2,6-3,2 i always go for 2,4-2,5.
if i do a taste test after only 1-2 weeks of bottle conditioning the amount of carbonation is perfect, but as times goes on it becomes to much

 

[mac_1103]

since my beers are all over carbonated and i always go to the lower end of the priming sugar calculator this seemed like a likely culprit. i am not a fan of highly carbonated beers so if i have a style that should be carbonated between 2,6-3,2 i always go for 2,4-2,5.

ISTM that 2-5 days at 0-2 PSI is not at all the likely culprit, because that is not nearly long enough to reach equilibrium.

Have you ever tasted a beer before you bottled it to see what the carbonation level was like? If you have a regulator that is really accurate, precise and stable at 2 PSI, and you crash for 2-3 weeks instead of days, then your beer should end up with something like 1.9 volumes of CO2. But that would probably create some issues when you try to bottle.

IMO the more likely culprit is that you just don't like your beer very fizzy. Why not try shooting for 2.0 - 2.2 volumes on your next batch? I suppose another possibility is that your beer hasn't completely finished fermenting when you crash and that is causing the additional carbonation, but I assume you're monitoring that.

 

[DuncB]

Are any of the beers dry hopped?
Are you spunding the beers at 2psi and then cold crashing keeping at 2psi.
I think this would increase your apparent vols and hence could skew your carbonation calculator for sugar.
@doug293cz produced a spreadsheet that works well for me with spunded beer that I then also counter pressure bottle and prime for high vols Belgian beers.

 

[user 346130]

Hello,Shotgun Craig here. I have a few questions. I started a dockelwiezen, but decided to modify the recipe by adding 4lbs.of light brown sugar and 2 jars of molasses to the original recipe..I just transferred it to a secondary fermenter today. It started working soon after. I tasted it and it's got a good bite to it. My alcohol level is about 13.8% . I started it a week ago Sunday. Should I add some coffee and sugar to smooth the taste or should I let it finish and deal with it then? Any ideas,thoughts or suggestions will be appreciated. Thanks

 

[mashdar]

Fermenters usually have a much higher area:volume ratio than a corny keg. I think 5 days will basically be at equilibrium if you're in a "normal" fermenter. I'll post empirical backup in a few weeks.

I use a keg carb chart to figure out the CO2 already in the beer. Then I use the priming calculator to get the volumes delta that I need. (The volumes from sugar are fixed regardless of starting CO2, within reason.)

E.g. if I have 1.8 vols residual, and I want 2.5, I adjust the priming calculator to add 0.7 volumes to whatever the "residual" CO2 in the calculator is.

You could also figure ~0.6 volumes per 0.001 gravity, and use PPG for your sugar to get the volumes you want to add.

 

[Adra]

Are any of the beers dry hopped?
Are you spunding the beers at 2psi and then cold crashing keeping at 2psi.
I think this would increase your apparent vols and hence could skew your carbonation calculator for sugar.
@doug293cz produced a spreadsheet that works well for me with spunded beer that I then also counter pressure bottle and prime for high vols Belgian beers.

i dry hopped a Saison a while ago, but i wasn't able to cold crash back then. carbonation of all my beers before i could cold crash was pretty good. i only started to get problems after i could cold crash with added co2 for positive pressure. i think I'm gonna start to never carbonate my cold crashed beers more then 2 vols and go from there. I have a dark mild in the fermenter as we speak, witch i would like to have at 1,8 vol so I'm gonna try to add priming sugar for 1 vol

 

[Adra]

Fermenters usually have a much higher area:volume ratio than a corny keg. I think 5 days will basically be at equilibrium if you're in a "normal" fermenter. I'll post empirical backup in a few weeks.

I use a keg carb chart to figure out the CO2 already in the beer. Then I use the priming calculator to get the volumes delta that I need. (The volumes from sugar are fixed regardless of starting CO2, within reason.)

E.g. if I have 1.8 vols residual, and I want 2.5, I adjust the priming calculator to add 0.7 volumes to whatever the "residual" CO2 in the calculator is.

You could also figure ~0.6 volumes per 0.001 gravity, and use PPG for your sugar to get the volumes you want to add.

a nice formula combining surface area, temperature, pressure, time and co2 would be lovely if something like that exists, havent found anything useful so far

 

[mashdar]

edit: wow. "Fix it" button on Android is basically a "blow up formatting" button.

I just posted a thread two days ago about formulas for pressure : temperature : volumes! https://www.homebrewtalk.com/threads/preferred-co2-concentration-calculation-method.734010/

Describing time may be very hard. With good mixing, it's probably a relatively simple asymptotic with an out-front constant for surface area : volume. But if we can't assume good mixing, it devolves into diffusion, convection, etc. That could devolve into vessel shape, temperature swings, etc being significant. It's possible that the time scale for mixing is short compared to the time scale for CO2 diffusion, but I wouldn't hang my hat on it.

 

[DuncB]

I thought that headspace had also been mentioned for this issue as a factor to consider.

 

[mashdar]

I thought that headspace had also been mentioned for this issue as a factor to consider.

If crashing a spunded beer, it does.

It sounds like OP is maintaining constant pressure from an external source, so the headspace volume won't matter (other than possibly affecting the liquid surface area, e.g. if this was calculus class and the beer was in a cone-shaped fermenter).

 

[DuncB]

Just moved a tafelbier to cold crash.
These ferment very fast as only low abv, I was a little late getting the spund valve on this and the gravity on the ispindel had plateaued,
however a week later with no gravity change the psi is now up to 15.
This unseen fermentation produces a lot of gas, could be a reason for the overcarbonation seen in the bottles.