The effects of cold crashing on priming sugar needs

I bottled a APA right out of my ice cold (actuary colder) mini fridge today and primed it for 2.5 volumes using 75F for residual C02. I know from experience that it will be close to 2.5 and obviously not the 3.4 that it would have been calculated at 32F.

An interesting discussion - it seems to me if you cold crash the beer even at a standard 1 atmosphere of pressure, it will absorb the CO2 from the headspace.

Basic physics indicates that this case is no different than the closed system keg, except the beer is always at 1 atmosphere of pressure, and (unfortunately) oxygen can be added to the system via the airlock as the fermentation vessel is chilled and CO2 headspace is absorbed by the beer.

I have not done the actual calculation of volumes of CO2 reabsorbed, but I would be concerned that you might absorb the entire CO2 headspace in a small vessel during the cold crash and introduce oxygen into the fermenter via the airlock. This could break the CO2 blanket over the beer, potentially leading to oxidation or potential contamination.

While the contamination risk is low near freezing, I generally try to keep oxygen away from fermented beer. Henry's law tells us that Oxygen is soluble in water, so if you do actually absorb the entire CO2 headspace, then oxygen will be absorbed by the finished beer. This might explain why some cold crashers are seeing lower carbonation in the finished beer than a straight CO2 temperature calculation might dictate.

Personally when I cold crash my beer, I usually will transfer it to a keg and pressurize it a bit first with Co2 to force all of the oxygen out and avoid any potential issues.

Cheers,
Brad

I don't keg. I generally cold crash in secondary with no head space. Suck back is near zero as I would assume is oxidation or carbonation.


Edit:
The Pale Ale I bottled at 32F and primed for a residual C02 at 75F seems to be very near the calculated 2.5 volumes (and T-58 has cleared out of the place--it's done and just a residue.)
T-58 rocks. :rockin:

late noob comment.
Based on the topic, and advanced level of the posters, I"m calling this thread "Crash of the Titans".

z987k said:

However the fact remains that if fermentation is complete and you crash cool, you will not magically get co2 from absolutely nowhere to dissolve into solution. That is physics and it's rather simple, with not much need for math, it's more of a concept.

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This sums up the situation perfectly I believe. Crash cooled beer may absorb a tiny amount of co2 back into solution but the amount of co2 available to reabsorb is tiny and it is not going to pull it out of co2-thin air. The amount of headspace in my carboy while crash cooling is a few ounces. This, if absorbed would account for less than .01 of a volume in the beer.

Saying that because Palmer or BeerSmith say carb level is determined by temp at bottling it must be true is just wrong. They should be corrected so that they stop disseminating false info. There are also credible sources that claim that the warmest temp should be used for calculations.

Especially we here at HBT, who continually claim that we know better than the so-called experts.

I keg and before I crash cooled all of my beers I used the carbing calcs of BS and they worked for me. So before when I kegged my Ordinary bitters BS would tell me to set my regulator at 11 psi to achieve 1.5 vols of carb. My carb level would be perfect at about 7-10 days. I used the temp at kegging even though I would be refrigerating the keg.

When I started crash cooling I went to use BS and it told me to set the pressure at .02 psi(!) to achieve 1.5 vols of carb. Guess what would happen if I set the pressure to .02 on crash cooled beer. Absolutely flat beer.

For corn sugar calcs the numbers are even more stark. BS says to put in NEGATIVE .25 oz of sugar to achieve 1.5 vols of carb at 36 degrees. This is obviously wrong as there is no way that my beer is sitting there just naturally carbed at 1.6 volumes.

In short Beer Smith is wrong in how they calculate carb. If you crash cool and use that temp in determining co2 pressure, or priming amount you will have a different level of carbonation than they lead you to believe.

The implications here that beer will reabsorb dispelled co2 on a drop in temperature imples that in a crash cool situation with small headspace the beer will be subject to oxidation. Based on my own observations alone I disagree with this. My crash cooled beers show no more evidence of oxidation than my non-crashed beers. I have no scientific basis for this observation, just my tastebuds, which I trust.

One of the things I have learned most implicitly from basically living at this website is not to blindly believe as gospel everything said by Parker and Papazian and brewing software.

One last thing to consider. As liquids sit still dissolved gas will tend to come out of solution. Fresh water will lose its oxygen and become stale as it sits. Beer and wine will lose CO2. Wine makers count on this as they know that the longer a wine ages the less necessary it becomes to de-carb it before bottling.

dontman said:

One last thing to consider. As liquids sit still dissolved gas will tend to come out of solution. Fresh water will lose its oxygen and become stale as it sits. Beer and wine will lose CO2. Wine makers count on this as they know that the longer a wine ages the less necessary it becomes to de-carb it before bottling.

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Does it "tend" to come out of solution? Or is it "tending" to equalize with the outside air, which normally just happens to mean off-gassing? I don't really understand what I'm saying but it seems reasonable...

I really think the point is just going with the highest temp the green beer has stabilized at. It's not necessary to be perfect. I usually shoot for 2.5, if I want more carbonation I go for 2.7. If it's Belgian or a German Wheat I go for 3-4. Some others I'd use 2.2 (and that may be high for some English ales.) If I'm off a tenth or two it doesn't even matter but that is the margin of error.

Actually when you think about it the answer is VERY simple! Not that complicated at all:

If you are fermenting a beer at 45F and you keep it at exactly 45F all the way through fermentation then you would use that as your bottling temperature entry in a priming calculator. Obviously because at 45 it holds a certain amount of Co2.

However, If you ferment at 68F and then crash cool to 35F and bottle at 35F you would still use the temp you fermented at 68F because at 68F it only holds a certain amount of Co2. (which is what the calculators ask for! Fermentation temp)

One myth to dispell: The shrinking headspace myth. This is thermal phenomena only! even if the beer absorbs Co2 it is still going to stay the same size. The Co2 is not going to magically dissapear into the beer and there will be less space. It is still in the carboy and takes up the same amount of space weather it is sitting on the beer or in the beer. What you are witnessing is the shrinkage of the molecules. That occurs simply because the temperature is lower.

The reason these recipes (at least for people who bottle condition) ask for the fermentation temp and not the current temp is because once the beer reaches a higher temp say 68F you lose Co2. Dropping the temperature does not give you more Co2. Just like the guy in AnoldUR's letter stated.... you would be undercarbonating because that Co2 has already been released. That is why they build their software that way. And scientifically it makes perfect sense. afterall, fermentation has ceased. if it was still fermenting and generating Co2 you could type that temp in (the fermentation temp)

As you ferment you reach a point where the beer has REALLY absorbed alot of Co2. As fermentation ceases so does the amount of Co2 based on the temperature of the beer. It leaves the fermentation vessel. The airlock will only hold a TINY amount in. Which is why they say commonly that it covers your beer. Its not under any significant pressure at all.

Its that simple! You can witness these exact same things happen as you leave a can of soda or beer on a counter top..... As you watch your windows contract during the winter........ as you type in the temp of the beer at fermentation (which is what they ask for) and get a perfectly carbonated ale.

Could this be true? I am open for suggestions and criticism of course!

as_saturn_ascends said:

Actually when you think about it the answer is VERY simple! Not that complicated at all:

If you are fermenting a beer at 45F and you keep it at exactly 45F all the way through fermentation then you would use that as your bottling temperature entry in a priming calculator. Obviously because at 45 it holds a certain amount of Co2.

However, If you ferment at 68F and then crash cool to 35F and bottle at 35F you would still use the temp you fermented at 68F because at 68F it only holds a certain amount of Co2. (which is what the calculators ask for! Fermentation temp)

One myth to dispell: The shrinking headspace myth. This is thermal phenomena only! even if the beer absorbs Co2 it is still going to stay the same size. The Co2 is not going to magically dissapear into the beer and there will be less space. It is still in the carboy and takes up the same amount of space weather it is sitting on the beer or in the beer. What you are witnessing is the shrinkage of the molecules. That occurs simply because the temperature is lower.

The reason these recipes (at least for people who bottle condition) ask for the fermentation temp and not the current temp is because once the beer reaches a higher temp say 68F you lose Co2. Dropping the temperature does not give you more Co2. Just like the guy in AnoldUR's letter stated.... you would be undercarbonating because that Co2 has already been released. That is why they build their software that way. And scientifically it makes perfect sense. afterall, fermentation has ceased. if it was still fermenting and generating Co2 you could type that temp in (the fermentation temp)

As you ferment you reach a point where the beer has REALLY absorbed alot of Co2. As fermentation ceases so does the amount of Co2 based on the temperature of the beer. It leaves the fermentation vessel. The airlock will only hold a TINY amount in. Which is why they say commonly that it covers your beer. Its not under any significant pressure at all.

Its that simple! You can witness these exact same things happen as you leave a can of soda or beer on a counter top..... As you watch your windows contract during the winter........ as you type in the temp of the beer at fermentation (which is what they ask for) and get a perfectly carbonated ale.

Could this be true? I am open for suggestions and criticism of course!

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I would say that practically this is correct, but still a gross oversimplification. The CO2 does not "magically" redissolve into the beer, but given a long enough time at this colder temp, more of the CO2 will diffuse into the beer - it is "simple" chemistry/physics and is true regardless of the amount of headspace shrinkage. I haven't done the math, but I imagine most people are not keeping their beer at this cold temperature for long enough for the new CO2 equilibrium to be reached. So, in short, the CO2 WILL do back into the beer if given enough time, but you probably don't need to worry about that and should calculate your priming based on the fermentation temp.

JLem said:

I would say that practically this is correct, but still a gross oversimplification. The CO2 does not "magically" redissolve into the beer, but given a long enough time at this colder temp, more of the CO2 will diffuse into the beer - it is "simple" chemistry/physics and is true regardless of the amount of headspace shrinkage. I haven't done the math, but I imagine most people are not keeping their beer at this cold temperature for long enough for the new CO2 equilibrium to be reached. So, in short, the CO2 WILL do back into the beer if given enough time, but you probably don't need to worry about that and should calculate your priming based on the fermentation temp.

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EXACTLY! I think you said it! For me though, I just can't believe that there is enough Co2 in the headspace to account for the difference in volumes of Co2 that I am getting out of a calculator. There simply isn't enough pressure inside the carboy (as a matter of fact there is hardly any) but I will agree that the Co2 is obviously trapped in the headspace and as temperature goes down Co2 absorption goes up.

I just bottled up a test batch of ale that we can test this out on.
According to the priming calculator located at: http://www.tastybrew.com/calculators/priming.html I should have 2.7 volumes of Co2 by adding 4.9oz. corn sugar using the fermentation temperature as a variable; 68F was my exact fermentation temp. I don't believe the beer was ever over 68F. However, if we take into account the temperature at which I bottled my brew,40F, and use that to calculate adding 4.9oz. of corn sugar the calculator gives me the figure of 3.3 volumes of Co2.

Now that is a VAST difference! 2.7 for ferm temps and 3.3 for bottling temp.

Either way, I added 4.9oz. of corn sugar and I will be able to tell the difference between 2.7 and 3.3 volumes of Co2.

I will post the results here in a month or so when I crack it open!

I still think the answer is fairly simple. Wort is saturated with Co2 as the yeast makes it during initial vigorous fermentation and absorbs alot of that. It can hold more at cold temps. But when you warm it up it leaves the wort. While it may absorb minimal amounts from the headspace, I don't believe it is anything worth taking into account in your beermaking.

This is the science forum though! it would be nice if we could have some lab tested experiments. If anyone has the equipment I think the answer would surely be appreciated in the field of beermaking.

as_saturn_ascends said:

One myth to dispell: The shrinking headspace myth. This is thermal phenomena only! even if the beer absorbs Co2 it is still going to stay the same size. The Co2 is not going to magically dissapear into the beer and there will be less space. It is still in the carboy and takes up the same amount of space weather it is sitting on the beer or in the beer. What you are witnessing is the shrinkage of the molecules. That occurs simply because the temperature is lower.

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So how can I get 2.5 volumes of Co2 into beer if it doesn't take up less space when it is absorbed? Also it's not the shrinkage of molecules, it is simply that they have less energy so occupy a smaller space.

conpewter said:

So how can I get 2.5 volumes of Co2 into beer if it doesn't take up less space when it is absorbed? Also it's not the shrinkage of molecules, it is simply that they have less energy so occupy a smaller space.

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how much space it takes up has nothing to do with how many volumes of Co2 you can fit inside of it. I can fit more rocks inside my carboy and the level keeps rising. Although, I am sure it is somewhat relative. (Co2 volume and beer volume)

I never thought of the lesser energy thing. Good post man! Very Interesting. After reading this I am beginning to wonder if JLem is onto something.............. there may just be enough Co2 in the headspace to be absorbed over a long period of time.........

man what good conversation this thread has generated

as_saturn_ascends said:

I just bottled up a test batch of ale that we can test this out on.
According to the priming calculator located at: http://www.tastybrew.com/calculators/priming.html I should have 2.7 volumes of Co2 by adding 4.9oz. corn sugar using the fermentation temperature as a variable; 68F was my exact fermentation temp. I don't believe the beer was ever over 68F. However, if we take into account the temperature at which I bottled my brew,40F, and use that to calculate adding 4.9oz. of corn sugar the calculator gives me the figure of 3.3 volumes of Co2.

Now that is a VAST difference! 2.7 for ferm temps and 3.3 for bottling temp.

Either way, I added 4.9oz. of corn sugar and I will be able to tell the difference between 2.7 and 3.3 volumes of Co2.

I will post the results here in a month or so when I crack it open!

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OK! Results are in..................... 2.7 volumes of co2 without a doubt. Its just about the right carbonation for this style of beer. Just wanted to let you all know the results of my little test for what its worth.

So for clarification, say I need to ramp up the temp of the beer I'm fermenting to the upper 80s during primary, then I let that fall back down to room temp AFTER fermentation is complete. Should I use the max. fermentation temp or the room temp of the beer?

cjalderman said:

So for clarification, say I need to ramp up the temp of the beer I'm fermenting to the upper 80s during primary, then I let that fall back down to room temp AFTER fermentation is complete. Should I use the max. fermentation temp or the room temp of the beer?

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I would use the max temp. As the beer warms up, it is not able to hold as much co2, so the co2 offgasses. This leaves less co2 in the beer, which isn't going back in anytime soon after you return it to room temp. Since the beer now has less co2 in it you need to add more sugar for the yeast to ferment to reach your target carbonation level.

Awesome, thanks for the reply!