The effects of cold crashing on priming sugar needs

[Malticulous]

I've bottled cold a number of times and used what I thought was the highest temp that the CO2 had stopped gassing off. Near as I call tell it works. Some times the calculated priming temp is 75F and I bottled at near freezing. The difference would be noticeable to me if I was wrong.

 

[MX1]

Just to add some more fuel to the fire....

If you pull up the carb calculator on Beer Alchmey there is a "*" noted next to the Temp input box; the note at the bottom says

*For beers being primed the temperature required in the fermentation tempreature.
For beers being forced carbonated the tempreature required is that of the beer in the keg during carbonation.

Not sure if this helps or hurts the discussion....

Tim

 

[AnOldUR]

I think this is the important point. Given enough time, the colder beer will absorb CO2 back into solution until equilibrium is reestablished, based on Henry's Law. The problem is knowing how much time it takes?.

From Wikipedia on Henry's Law:
At a constant temperature, the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid. An equivalent way of stating the law is that the solubility of a gas in a liquid at a particular temperature is proportional to the pressure of that gas above the liquid.

Thanks for the links. Good reading here.

Although, as you say, the time is very important to our cold crashing application, but wouldn't pressure and volume of the gas available be more important? I'm trying to find something to convince me that any of the CO2 in the head space will be absorbed or if the thermal effects on pressure from chilling a closed system create an equilibrium where the CO2 in suspension remains constant at its pre chilled state.

A question to other who have cold crash in a glass carboy. Does the liquid in your airlock get sucked into your carboy, or just move in that direction, but not enough to empty the chamber?

Am I correct in assuming that head space pressure would drop if CO2 were absorbed?

 

[z987k]

A question to other who have cold crash in a glass carboy. Does the liquid in your airlock get sucked into your carboy, or just move in that direction, but not enough to empty the chamber?

Am I correct in assuming that head space pressure would drop if CO2 were absorbed?

I don't get any suckback. It does however move in that direction depending on atmospheric pressure. The small amount of negative pressure that thermal compression of both the liquid and headspace create is small enough that it is completely negated by day to day(hourly sometimes) changes in atm pressure.

If CO2 were absorbed, naturally the partial pressure of co2 in a sealed environment would also drop which would make the liquid release some co2, there would have to be an equilibrium point somewhere and because we have no idea the amount of co2 in the headspace (and no idea what volumes of co2 are anyways) we have no idea how much residual co2 is in the beer except that it cannot be more that what is possible to absorb at 1atm and the highest temperature ever achieved.

Here's an easy way to look at this:
The beer was fermented and then left to sit after fermentation for 1 week at 68F. This gives us .8 volumes of co2. Lefts say for fun there is .6 volumes in headspace. If you chill the beer to 40F, it will not absorb those .6 volumes because it will lower the partial pressure of co2 in the headspace below 1atm which then changes the amount of co2 the liquid can hold. We would need to extend that chart and find where the partial pressure of co2 in solution equals the partial pressure in the headspace at 40F. Then as kaiser said, this doesn't happen instantly, it takes time to reach that equilibrium point.

And last, why on earth are we referring to co2 in volumes. Volumes! Maybe I should refer to my beer in volumes. I made 123097854320 volumes of beer today. How much is that? No one knows, it's my own super secret standard unit of measurement! If I tell you I put 27oz of hops in 72 volumes of beer, you would ask, how much beer is that, because volumes is not a unit of measurement! I mean seriously, wtf, who refers to something in units that are meaningless. And why does everyone use the useless unit? Did someone decide that the world is unable to comprehend what a liter or cu. ft are?

and after some googling I found that the commonly referred to

"volumes", means liters of co2 per liter of liquid. So L co2/ L beer. Now maybe we can do math if need be. It also means that my .6 volumes in the paragraph above is not used correctly in the slightest, but I think the message is still conveyed.

 

[Gremlyn]

Interesting, so when we are saying we carb 5 gal of beer to 2.5 volumes of CO2, we are really creating ~47 litres of CO2. Of course, this is usually split per bottle. It would make sense that the CO2 to liquid ratio would have to be pretty high to create of a difference to get enough CO2 into solution.

So now we know what volumes are... do we know if we are attempting to get that many volumes into solution or just create that many volumes and get as much in as possible.

 

[conpewter]

I don't get any suckback. It does however move in that direction depending on atmospheric pressure. The small amount of negative pressure that thermal compression of both the liquid and headspace create is small enough that it is completely negated by day to day(hourly sometimes) changes in atm pressure.

If CO2 were absorbed, naturally the partial pressure of co2 in a sealed environment would also drop which would make the liquid release some co2, there would have to be an equilibrium point somewhere and because we have no idea the amount of co2 in the headspace (and no idea what volumes of co2 are anyways) we have no idea how much residual co2 is in the beer except that it cannot be more that what is possible to absorb at 1atm and the highest temperature ever achieved.

Here's an easy way to look at this:
The beer was fermented and then left to sit after fermentation for 1 week at 68F. This gives us .8 volumes of co2. Lefts say for fun there is .6 volumes in headspace. If you chill the beer to 40F, it will not absorb those .6 volumes because it will lower the partial pressure of co2 in the headspace below 1atm which then changes the amount of co2 the liquid can hold. We would need to extend that chart and find where the partial pressure of co2 in solution equals the partial pressure in the headspace at 40F. Then as kaiser said, this doesn't happen instantly, it takes time to reach that equilibrium point.

And last, why on earth are we referring to co2 in volumes. Volumes! Maybe I should refer to my beer in volumes. I made 123097854320 volumes of beer today. How much is that? No one knows, it's my own super secret standard unit of measurement! If I tell you I put 27oz of hops in 72 volumes of beer, you would ask, how much beer is that, because volumes is not a unit of measurement! I mean seriously, wtf, who refers to something in units that are meaningless. And why does everyone use the useless unit? Did someone decide that the world is unable to comprehend what a liter or cu. ft are?

and after some googling I found that the commonly referred to

"volumes", means liters of co2 per liter of liquid. So L co2/ L beer. Now maybe we can do math if need be. It also means that my .6 volumes in the paragraph above is not used correctly in the slightest, but I think the message is still conveyed.

Right volumes would be somewhat equivalent to ppm since it is a reference of concentration.

When I cold crash in primary it sucks in all the star-san in the airlock, so I don't know how much Co2 is absorbed. If the beer absorbs Co2 from the headspace (as equilibrium equations would show) it will then have a mixture of Co2, nitrogen, oxygen etc above the beer. At that point it has to come to equilibrium with that solution instead of pure Co2 so it won't come all the way down to the amount you would think based on the temp and an unlimited supply of pure Co2.

 

[Kaiser]

And last, why on earth are we referring to co2 in volumes. Volumes!

I don’t like the “volumes Co2” measure either. Expressing carbonation as % w/w or g/l CO2 is more practical. Especially if you know that each gram of sugar will get you ~0.5 g of CO2. Just calculate how many gram of CO2 are missing for the desired carbonation and multiply by 2 to get the amount of priming sugar (if you use table sugar) in gram. The conversion between g/l and vol CO2 is easy: 2 g/l CO2 = 1 vol CO2.

Kai

 

[AnOldUR]

If you pull up the carb calculator on Beer Alchmey there is a "*" noted next to the Temp input box . . . For beers being primed the temperature required is the fermentation temperature.

This discussion has run its course, but here's one more thing to add. Rather than just take it at face value, I wrote to Beer Alchmey questioning why they use the method of using fermentation temperature for making carbonation calculations, not the cold crashed temperature. Here is the response.

Hi Herman,

The reason for using the fermentation temperature is that it’s the limit to the amount of residual CO2 in the beer left after fermentation (CO2 is less soluble at higher temps). So we start with the residual CO2 and then work out how much CO2 we need to reach the desired carbonation. If you used the temperature you crash cooled to then the calculated residual CO2 would be higher but as it would be crash cooled there would be very little yeast activity to create additional CO2. So your beer when primed would be undercarbonated.

The CO2 in the head space could be absorbed but it’s unlikely to make much difference on the calculations unless the CO2 was being replenished as it was absorbed (as when force carbonating in keg).

Cheers

Steve Flack
Kent Place Software

As a side note, I also contacted BeerSmith, to ask for an explanation of their instructions, but Brad did not respond to the HBT PM (he might not be that active here), so I just tried an email.

 

[AnonyBrew]

So to get this all straight, if I ferment at 70F until fermentation is complete, then crash cool to 36F for 1 week, then pull the carboy out of the fridge and bottle it within the hour I should be using about 38-40F (guesstimate) for the priming calculator (given that the beer will rise a few degrees while racking, capping, etc.). If it takes me an hour to bottle this makes it difficult since the beer temp. will rise as I bottle. So beer #1 will be at a cooler temp. than beer #50.

If I let the cold crashed beer warm back up to 75F (my room temp.) before bottling, how long does it take the CO2 to outgas before the charts/calcs. can be used? 1 hr? 2 hrs? 8 hrs?

 

[JLem]

So to get this all straight, if I ferment at 70F until fermentation is complete, then crash cool to 36F for 1 week, then pull the carboy out of the fridge and bottle it within the hour I should be using about 38-40F (guesstimate) for the priming calculator (given that the beer will rise a few degrees while racking, capping, etc.). If it takes me an hour to bottle this makes it difficult since the beer temp. will rise as I bottle. So beer #1 will be at a cooler temp. than beer #50.

If I let the cold crashed beer warm back up to 75F (my room temp.) before bottling, how long does it take the CO2 to outgas before the charts/calcs. can be used? 1 hr? 2 hrs? 8 hrs?

if you ferment completely at 70, and then cold crash, use 70 for setermining carbonation. If you use the cold crashed 36 degrees your beer will likely be undercarbonated because there isn't as much residual CO2 in there as the chart says (because all the CO2 was produced at 70 degrees and 70 degree liquid cannot hold as much CO2, most of it was outgassed. Cold crashing for a week will result in minimal additional CO2 absorption.

 

[Malticulous]

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.

 

[BeerSmith]

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

 

[Malticulous]

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:

 

[zakleeright]

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

 

[dontman]

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.

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.

 

[Ketchepillar]

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.

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...

 

[Malticulous]

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.

 

[as_saturn_ascends]

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!

 

[JLem]

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!

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.

 

[as_saturn_ascends]

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.

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.

 

[conpewter]

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.

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.

 

[as_saturn_ascends]

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.

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]

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!

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.

 

[cjalderman]

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?

 

[JLem]

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?

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.

 

[cjalderman]

Awesome, thanks for the reply!