The effects of cold crashing on priming sugar needs

Here’s a little debate from over in General Techniques that could use a science-based answer. The question was, "Do I need to bring my beer back to room temperature before I bottle?"

The apparent answer is "no", but the question that comes up next is, does the amount of priming sugar needed change because the beer is cold?

We know that carbonation level is determined by adding the residual CO2 to the amount of carbonation gained from the priming sugar. The carbonation gained from priming is easy to calculate, but the residual amount is what is in question. What’s been suggested in the quotes below is that chilling the beer after it has finished fermenting will add volumes of CO2.

My perspective is that the chart Revvy linked to is referring to amount of CO2 that the beer has the ability to hold at a given temperature and pressure. Not that it will change to that volume of CO2 just because the temperature was changed after fermentation stopped. If the beer warms too much in the carboy after fermentation has stopped it will off-gas CO2 and that CO2 is lost forever. If you chill this beer and don’t add CO2 under pressure, it’s not going to become more carbonated. It has the potential to hold CO2, but only if it is applied under pressure. I interpret the chart to represent the volumes of CO2 placed in the beer by the fermentation process and it’s ability to hold those volumes at the given temperature and pressure combinations.

So, what’s the answer? Is there a legitimate reason to change the amount of priming sugar used if a beer is cold crashed after fermentation is complete? Or do you base you priming sugar calculation on the beers CO2 content before cold crashing?

Revvy said:

...but really, if you want it carbed "right" then let the beer warm back up...

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Revvy said:

. . . if the beer changes temps (which it does) it lets go or absorbs more co2.

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greenbirds said:

Careful, When you crash cool the beer absorbs a lot of CO2. As it warms up it off-gasses, but don't expect it to be at its normal (for room temp) CO2 level once it reaches room temp

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But if you wanna get people up to speed maybe you should quote something a little more of the counter discussion then just the little bit you quoted by me, and YOUR data....

Here's what is confusing, you wonderful science gurus, for a lot of us..when using Palmer's Monograph OR Beersmith where it asks for the "temp of the beer," exactly what temp is it asking you for?

The argument comes down to are you using the temp of the beer it was fermented at or bottling time?

The esteemed brewer from the state of NJ, AnOldUR, believes that it is the temp you fermented at. At one time I too believed that as well though it didn't make sense as I started carbing for style and imputting info into beersmith to figure out how much sugar to use....I have now swung to the other aisle and begun using the temp right at the time of bottling and I have had no issues with under or over primed bottles.....

Here's my "stuff" from the other thread...

Even Palmer's Carbonation Nomograph shows the affects of temp on carbonation and the amount of sugar needed at bottlig time based on temp. Like I said if you use the carbing feature on beersmith (and I assume other software) it always asks for the temp of the beer, in order to figure out the amount of sugar you need at bottling time.

Figure 65- Nomograph for determining more precise amounts of priming sugar. To use the nomograph, draw a line from the temperature of your beer through the Volumes of CO2 that you want, to the scale for sugar. The intersection of your line and the sugar scale gives the weight of either corn or cane sugar in ounces to be added to five gallons of beer to achieve the desired carbonation level.

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Accurately Calculating Sugar Additions for Carbonation - German Brewing Techniques

Accurately calculating the carbonation is a great exercise for working with apparent and true (or real) attenuations as well as working with the extract % or Plato scale. The latter is not essential, but makes the calculations more intuitive.

The final carbonation of bottle conditioned beer depends on the CO2 present in the beer at bottling time and the CO2 that will be generated during bottle conditioning.

The amount of CO2 already in the beer can be determined based on the CO2 head-space pressure and the temperature of the beer. It can be determined by using Carbonation Tables. These tables show the equilibrium of CO2 content that exists for a given CO2 pressure and beer temperature.

The amount of CO>sub>2</sub> created by bottle conditioning is based on the amount of sugar that is fermented. Each gram of fermentable extract is fermented into equal parts (by weight) of alcohol and CO2 (this is not exactly true, but close enough for this calculation).

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The Burgundian Babble Belt -- Pushing the Homebrew Envelope


Re: Carbonation, sugar and time
Follow the calculators that are based on temperature. I usually take my keg out of the chiller the day before and let it warm up to room temperature for the next day's bottling and then I add a little more sugar because the keg does vent when I open it up.

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It doesn't make sense that it would be based on fermentation temp. That's really has little relevance to the beers ability to hold or not hold co2 a month later at bottling time. It shouldn't matter because if the beer changes temps (which it does) itlets go or absorbse more co2. Like when a fermenter suddenly starts releasing more co2 if it gets warmer or sucks in the sanitization solution out of the airlock if it gets cooler. If you have a two piece airlock you can see the co2 variable swing back and forth between the two chambers, and that has to be related to the temp of the fermenter.

Your beer is constantly moving and shifting temp....But at bottling time you need to know EXACTLY where your beer is at in terms of how much co2 it is going to be able to absorb THEN. At THAT moment you take a snapshot and determine the gravity of the beer and it's temp. And that's when you determine how much sugar you need...NOT the condition of the beer way back then.

Don't forget the beer is going to be carbonating at about the "room" temp the fluid is. SO it is even more logical that you would calculate the amount of co2 at that temp by letting the beer get to the ambient temp, and then bottling.

It intrinsically makes more sense to me that you calculate it based on the condition of the beer at the moment you are choosing to bottle it


I'm no scientist, and I barely understand anything you guys talk about in this part of the forum....but I blame palmer for not specifying what he meant more clearly in the section on explaining the how to use the nomographs....

So I think my esteemed collegue is wrong in his choice of a thread title....I think should better be phrased as simply as;

When calculating the amount of priming sugar using Palmer's nomograph or beersmith, where it asks for "temp of beer" is it fermentation temp or present temp of the beer, that they are asking?

It doesn't matter to me whether anyone crash cools or not, what matters then is do you take the temp of your beer at that moment to figure out how much priming sugar you need to acheive the desired level of carbonation.

Meaning to me, if my beer is cold, I use x amount of sugar based on the nomograph, or beersmith, and if I have let my beer warm back up, I use that temp as the basis of determining the amount of sugar, and that will be more sugar....or do I ignore all of that, and look at my beersmith notes to see what temp I fermented the beer at a month ago. Seems to me that that is an irrevelant bit of info to base the amount of sugar on.

What he quoted me repeatedly out of context for the discussion was me suggesting that he warm it back up. I suggested that just because it was easier to calculate it at room temp, which is closer to the 4.5 to 5 ounces of sugar we usually use. Not that it was better or worse to leave it cold or room temp, but what you then use as your temperature to determine the amount of sugar to use.

To me it doesn't matter....I never said you HAD to warm it back up to bottle, I just said you had to determine how much sugar to used by taking a temp reading then and using that as your baseline.

For example, if my beer is NOW at 35 degrees, and I want 2.5 volumes of co2 Palmer appears to say I need about 2 ounces of priming sugar.

On the other hand my 70 degree beer evidently needs 4 ounces of sugar to get to 2.5 volumes.

using temp at bottling time as my basis.....


My only wish dear science wonks over here, is that when you finally finish your debate/discussions that you summarize it in plain enough english so we all can understand it.

Your beer is constantly moving and shifting temp....But at bottling time you need to know EXACTLY where your beer is at in terms of how much co2 it is going to be able to absorb THEN. At THAT moment you take a snapshot and determine the gravity of the beer and it's temp. And that's when you determine how much sugar you need...NOT the condition of the beer way back then.

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I agree that the conditions during fermentation, weeks prior, are not all that helpful with determing residual CO2. However, the problem with looking just at the current conditions (i.e. my beer is now at 64 degrees F) is that if the temp of the beer has changed appreciably, the now-64 degree beer, may not contain as much residual CO2 as a beer that has stayed consistently at that temp. If it has warmed up to beyond that and cooled back down - after fermentation was completed - it will have lost CO2 during the warm-up phase and just because it is now back to 64 degrees does not mean the CO2 will be redissolved - most likely it was lost via the airlock or, if not, it's just sitting there above the beer. It's kinda like leaving an open bottle of soda on the counter for a couple of days and then popping it back in the fridge and expecting it to recarbonate. Not going to happen.

So, this is my take:

A) If your beer has stayed at a constant temp, no need to fret about anything, just use the carb tables as intended.

b) If your beer was kept cooler than the temp you are bottling at (i.e. you crash-cooled and then brought the beer up to room temp before bottling), use the temp your beer is currently at (CO2 would be lost as it warmed up, but it would still contain the expected residual amount at the current temp)

c) If your beer was kept at a higher temp than you are now bottling (not sure when this might be the case - a saison or belgium perhaps?), you will need to add some additional priming sugar to get the desired volumes of CO2, because the beer will not have the residual CO2 you think it does. How much more? Beats me - will depend on the specific temps.

I imagine option c) applies to a very small percentage of beer. And even then, I imagine adjustment would be unnecessary as any difference in carbonation would be practically unnoticeable

I believe it is asking for the temperature at which the beer will sit during carbonation. The two previous temperatures should have little bearing as they don't magically infuse a property in the beer that comes into play with the CO2 later. I've not done any scientific research into this, but I do have a background in microbiology and worked in a lab for a long time. My assumption has been that the temperature you allow the beer to carbonate at will determine the yeast activity level, which will in turn determine the amount of CO2 produced.

The only argument I can see in favour of accounting for the temperature at bottling time is if you cold crashed it, because then you have absorbed some CO2 into the beer. If you then bottle the beer at this temperature, you're prematurely adding CO2. The only problem is finding out how much CO2 is in there.

Gremlyn - I disagree. The temp your are carbonating at has little bearing on this, assuming 1) the bottles are capped properly and thus under pressure as the CO2 builds and 2) the yeast are (and remain) active. It may take longer to carb up at colder temps, but that's because of the yeast metabolism. Higher temps can hold less CO2 given a particular pressure, but as the amount of CO2 builds up, the pressure does as well, leading to the CO2 dissolving into the beer (up to a point of course and as long as the pressure does not build up enough to create bottle bombs).

The reason for the tables is to determine how much CO2 is already in the beer, which is currently NOT under pressure. Therefore, the temp the beer is at, assuming completed fermentation, will tell you how much CO2 is left dissolved in there, thus how much more you want/can add to get to a particular carbonation level. The temperature on the charts is the temperature your beer is at the time of bottling (and thus putting under pressure).

OK, that makes sense, and you don't entirely disagree with me Your explanation of the purpose for the tables goes along with my point in my second paragraph, and answers my question of finding the leftover CO2 in the beer. I suppose we should consider total carbonation an absolute based on a given amount of sugar added and active yeast. I think that the first table should always be used at 0 head pressure at bottling time in this case, you're going to release some CO2 when racking to the bottling bucket anyway, so even if you rack immediately after opening the carboy/pail the head pressure is nil and the beer is likely equilibrated to such by the time you bottle.

JLem said:

I agree that the conditions during fermentation, weeks prior, are not all that helpful with determing residual CO2. However, the problem with looking just at the current conditions (i.e. my beer is now at 64 degrees F) is that if the temp of the beer has changed appreciably, the now-64 degree beer, may not contain as much residual CO2 as a beer that has stayed consistently at that temp. If it has warmed up to beyond that and cooled back down - after fermentation was completed - it will have lost CO2 during the warm-up phase and just because it is now back to 64 degrees does not mean the CO2 will be redissolved - most likely it was lost via the airlock or, if not, it's just sitting there above the beer. It's kinda like leaving an open bottle of soda on the counter for a couple of days and then popping it back in the fridge and expecting it to recarbonate. Not going to happen.

So, this is my take:

A) If your beer has stayed at a constant temp, no need to fret about anything, just use the carb tables as intended.

b) If your beer was kept cooler than the temp you are bottling at (i.e. you crash-cooled and then brought the beer up to room temp before bottling), use the temp your beer is currently at (CO2 would be lost as it warmed up, but it would still contain the expected residual amount at the current temp)

c) If your beer was kept at a higher temp than you are now bottling (not sure when this might be the case - a saison or belgium perhaps?), you will need to add some additional priming sugar to get the desired volumes of CO2, because the beer will not have the residual CO2 you think it does. How much more? Beats me - will depend on the specific temps.

I imagine option c) applies to a very small percentage of beer. And even then, I imagine adjustment would be unnecessary as any difference in carbonation would be practically unnoticeable

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I agree entirely with this. While I was reading Revvy's post this is essentially what was turning in my mind.

If c is the case, it is really hard to determine(which i think is the base of the whole thing here). You would need to know the highest temperature your beer ever achieved after fermentation stopped, and from there it could not have more than the 0psi volume for that temp.
So if you have your beer at 70F solid after fermentation, you cannot have more than .8 volumes even if you crash cool to 34.
Just because you crash cool does not mean co2 is suddenly dissolved into solution to the volumes of that temperature. Where did the co2 come from?

z987k said:

Just because you crash cool does not mean co2 is suddenly dissolved into solution to the volumes of that temperature. Where did the co2 come from?

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This is exactly my point. Especially if you cold crash in your secondary with no head space. If you're not introducing new CO2, where are these additional volumes coming from? The thermal contraction from cold crashing has created a negitive pressure in the carboy, so even the head space CO2 will not be absorbed.

So, the highest temperature that your beer was at after fermentation is complete determines the volumes in suspension. You just have to add to that the amount of priming sugar needed to reach the style your brewing.

Still, it would be nice if someone with a science background would drop in here and confirm this.

AnOldUR said:

The thermal contraction from cold crashing has created a negitive pressure in the carboy, so even the head space CO2 will not be absorbed.

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I didn't even touch on this part. When you cool the liquid there will be a reduction in volume of the liquid which like AnOldUR said, create a negative pressure inside the carboy, and need to either off-gas a little co2 since the partial pressure of that gas is now lower or suck in some sanitizing solution and/or air to make up the space.

AnOldUR said:

This is exactly my point. Especially if you cold crash in your secondary with no head space. If you're not introducing new CO2, where are these additional volumes coming from? The thermal contraction from cold crashing has created a negitive pressure in the carboy, so even the head space CO2 will not be absorbed.

So, the highest temperature that your beer was at after fermentation is complete determines the volumes in suspension. You just have to add to that the amount of priming sugar needed to reach the style your brewing.

Still, it would be nice if someone with a science background would drop in here and confirm this.

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That makes perfect sense. Assuming your fermentation has completely stopped (which it should have), there is no new CO2 production. So whatever CO2 is inside the carboy at the end of the fermentation is all you have to work with. Going with the highest temperature of the beer post fermentation would be your best bet at getting your CO2 volumes where you want them.

I went to the horse's mouth...I knew you guys are all over complicatining things still...It occurred to me, that since I use Beersmith to figure it out, I should look at the beersmith help for THEIR definition of "Beer Temp."

AND I WAS RIGHT, Y'ALL!!!!! And I betcha if we emailed, Palmer, and asked him directly what HE means, he would say the same thing.

So here it is DIRECTLY from the instructions on my beersmith software.

Beersmith said:

Beer Temp - The temperature of the beer. For bottled beers, this is the temperature at bottling (usually room temperature). For kegged beers, this is the temperature at which the beer will be force carbonated, which may be either room temperature or refrigerator temperature depending on your keg setup.

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Not at fermentation, not at the highest temp, not at the coldest temp, not at the conjunction of the planets.....At the time I sit down and bottle!

FTW!

So, if you crash cool it and don't let it warm back up, then all you need to do is take a temp reading of the beer and calculate the amount of sugar (usually lesser) for the cold beer.

So going back to Palmer's Nomograph

Figure 65- Nomograph for determining more precise amounts of priming sugar. To use the nomograph, draw a line from the temperature of your beer through the Volumes of CO2 that you want, to the scale for sugar. The intersection of your line and the sugar scale gives the weight of either corn or cane sugar in ounces to be added to five gallons of beer to achieve the desired carbonation level.

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For example, if if I crashed cooled and just took it out and my beer is NOW at 35 degrees, and I want 2.5 volumes of co2, Palmer says I need about 2 ounces of priming sugar.

On the other hand my 70 degree beer needs 4 ounces of sugar to get to 2.5 volumes.

Revvy - I don't think we overcomplicated things, but rather Palmer and BeerSmith simplified things. If you crash cool to 35 degrees and bottle at 35 degrees, but your beer was at one point 70 degrees, you will not have as much CO2 in the beer as you think (CO2 will come out of solution at the higher temp and not go back into solution at the lower temp, unless there is still fermentation and/or you pressurize the beer). I imagine that Palmer and BeerSmith simplify it because that covers 99% of the bottling situations. I'm a relative newb, but how often is bottling done at a temp lower than room temp (which typically will be as warm as the beer has gotten)? And as far as kegging goes, I have no experience with this, so my statements apply only to bottle conditioning.

JLem said:

Revvy - I don't think we overcomplicated things, but rather Palmer and BeerSmith simplified things. If you crash cool to 35 degrees and bottle at 35 degrees, but your beer was at one point 70 degrees, you will not have as much CO2 in the beer as you think (CO2 will come out of solution at the higher temp and not go back into solution at the lower temp, unless there is still fermentation and/or you pressurize the beer). I imagine that Palmer and BeerSmith simplify it because that covers 99% of the bottling situations. I'm a relative newb, but how often is bottling done at a temp lower than room temp (which typically will be as warm as the beer has gotten)?

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BUT it verifies my initial statement/discussion with my esteemed collegue from the great state of New Jersey, the honorable (but wrong ) AnOldUR, as to what Beersmith or Palmer (we assume) meant.....And that's all I care about. I was doing it right, I was understanding it right, and when I advise people as to what to do, I will still be correct.

99% of the situations are good enough for me....If joe brewer brings his beer out of crash cooling and wants to bottle immediately without warming it up, he takes the temp of the beer at that moment and uses THAT NUMBER to calculate the amount of sugar. It doesn't matter that the beer was at 70 three weeks ago, or 2 days ago, if the beer is cold right now, they you use the amount of the sugar as per beersmith or the nomograph...if you let the beer warm up over night, you still take the temp AT THAT MOMENT, and use THAT TEMP for your sugar calculation...It IS that simple.

Revvy said:

I really don't care, my friend, if people think that Palmer or Brad of Beersmith is wrong...I only care that my interpretation of it is correct. Like I said earlier, it's worked for me, no undercarbed or bottle bombs.

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Palmer and Brad's writings are not wrong just incomplete. It is your blindly following your interpretation and then using it as fact to fit you argument that is wrong. I suspect that their information was written before cold crashing became a popular technique, so it was left out of consideration.

Revvy said:

AND I WAS RIGHT, Y'ALL!!!!!
FTW!

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I'm not here pounding my chest that my position is correct. It may not be. All you've done is produced quotes that contain no supporting data. This topic was brought to the science forum in search of fact based answers and I'm still hoping that will come.

Revvy said:

the honorable (but wrong ) AnOldUR.

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AnOldUR said:

I'm not here pounding my chest that my position is correct. It may not be. All you've done is produced quotes that contain no supporting data. This topic was brought to the science forum in search of fact based answers and I'm still hoping that will come.

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I think you are taking this way too freaking serious. I thought this was a friendly discussion between us right from the beginning, hence my calling you my ESTEEMED collegue And friendly jibbing....

And again, my original question as to how beersmith/Palmer's use of the word "Beer Temp" in those calculations is meant BY the people who came up with them...has been answered. Whether anyone thinks it is VALID or not is irrevelant to my initial point.

And has anyone ACTUALLY calculated "THEIR WAY" of doing things, and seen whether or not it comes out to be the same as these calculations????

Conroe in the other thread mentioned BYO's calculations....

http://***********/resources/carbonation

Like I said, I am not a scientist, and math makes me nauseous....so I am not going to run the numbers...and I really don't care if they match or not, because obviously there is more than one way to skin a cat in this...Perhaps just like there are different scales for IBU's Rager, Tinsteh, etc...there are more than one way to calculate carbonation...OR maybe Palmer/Beersmith took your way do doing things (figuring in excess co2) and came up with their calculators...and the numbers ultimately are close enough for government work.

My initial post in the other thread, and followed up in here, was that according to my interpretation of Palmer/Beersmith was what was THEIR intent in their use of the word beer temp...Well according the "definition of terms" in the beersmith helper document THAT IS WHAT BEERSMITH MEANS.

I don't know about Palmer, but if I can find his email addy I intend to ask him what he meant.

Revvy said:

I think you are taking this way too freaking serious.

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Isn't that what the science forum is for?

You've buried this and the other thread in enough of your ego to make it impossible to read and all but useless.

Thank you for that.

Revvy said:

I think you are taking this way too freaking serious. I thought this was a friendly discussion between us right from the beginning, hence my calling you my ESTEEMED collegue And friendly jibbing....

And again, my original question as to how beersmith/Palmer's use of the word "Beer Temp" in those calculations is meant BY the people who came up with them...has been answered. Whether anyone thinks it is VALID or not is irrevelant to my initial point.

And has anyone ACTUALLY calculated "THEIR WAY" of doing things, and seen whether or not it comes out to be the same as these calculations????

Conroe in the other thread mentioned BYO's calculations....

Brew Your Own: The How-To Homebrew Beer Magazine - Carbonation Priming Chart

Like I said, I am not a scientist, and math makes me nauseous....so I am not going to run the numbers...and I really don't care if they match or not, because obviously there is more than one way to skin a cat in this...Perhaps just like there are different scales for IBU's Rager, Tinsteh, etc...there are more than one way to calculate carbonation...OR maybe Palmer/Beersmith took your way do doing things (figuring in excess co2) and came up with their calculators...and the numbers ultimately are close enough for government work.

My initial post in the other thread, and followed up in here, was that according to my interpretation of Palmer/Beersmith was what was THEIR intent in their use of the word beer temp...Well according the "definition of terms" in the beersmith helper document THAT IS WHAT BEERSMITH MEANS.

I don't know about Palmer, but if I can find his email addy I intend to ask him what he meant.

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I'm sure you are right as to what Palmer and Beersmith are getting at because most people do not crash cool their beer, and it was probably even less likely when Palmer wrote his book. 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.

So in 99% of the cases... which I don't think is accurate, because 1 case is where the simplified way palmer puts forth does not account for cooling of the beer, and that is not 1% of the time.

Since we are in the science forum, I'm going to continue to argue my point, and I know I am right on this, barring some property of water to retain co2 beyond it's normal ability that I don't know about. If this was in general techniques or such, the real answer is what you said "good enough for government work" so who the hell cares. I mean in reality we're only talking about .4 volumes difference at the most.

AnOldUR said:

Isn't that what the science forum is for?

You've buried this and the other thread in enough of your ego to make it impossible to read and all but useless.

Thank you for that.

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Come on now, can't we get along. Our Esteemed Colleague Revvy is trying to argue a point that I think he really believes, and it's up to us to show him that he's wrong, not belittle him. Besides I agree with him on 99% of things anyways.
Nice to disagree once in awhile....but in the science forum, facts must prevail, it's not only about well in reality they both work and it doesn't matter.(which again is the case here.)

I wonder if this would need to take into account the headspace filled with Co2. So if I have beer at 70* with a certain headspace sitting at 1 atm, then move it to the fridge at 40* at 1 atm then it should absorb Co2 (slowly) from the headspace while pulling in air through the airlock (after sucking the water/sanitizer/vodka in). So if I have a huge headspace it should equalize out to having the amount of Co2 in solution that you would expect at 40*, if there was not enough headspace or time, then you'll have less Co2 in solution than you would calculate.

conpewter said:

I wonder if this would need to take into account the headspace filled with Co2. So if I have beer at 70* with a certain headspace sitting at 1 atm, then move it to the fridge at 40* at 1 atm then it should absorb Co2 (slowly) from the headspace while pulling in air through the airlock (after sucking the water/sanitizer/vodka in). So if I have a huge headspace it should equalize out to having the amount of Co2 in solution that you would expect at 40*, if there was not enough headspace or time, then you'll have less Co2 in solution than you would calculate.

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That is true as long as it sucks in some air past the airlock to make up for the loss in headspace. Otherwise it would create a negative pressure in the haedspace, which throws in the pressure back into our good friend pvnrt as it's no longer 0psi/1atm.

z987k said:

That is true as long as it sucks in some air past the airlock to make up for the loss in headspace.

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And at that point you're sucking in air, not CO2. The existing CO2 would blanket the surface, but the question is, is that nearly enough to make any difference or do you need a constant supply of pure CO2 at a constant pressure (even if that pressure is zero, so long as it's not negative) until the saturation point for that temperature has been reached?

z987k said:

Come on now, can't we get along. Our Esteemed Colleague Revvy is trying to argue a point that I think he really believes

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You are correct and I apologize for that. But you have to admit that Revvy's long and multiple posts dominate a thread to the extent that very few would have the patience to follow through to the end.

Revvy said:

...there are more than one way to calculate carbonation...OR maybe Palmer/Beersmith took your way do doing things (figuring in excess co2) and came up with their calculators...and the numbers ultimately are close enough for government work.

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There can't be more than one way to calculate carbonation, ultimately. I'm sure you can find a few different equations to fit the bill if you wanted to, but the end result will ALWAYS be the same. Calculation of gas in solution isn't subjective like calculating IBU's. You have ONE equation for finding out how much CO2 will be in your headspace in an ideal situation which is:

PV = nRT

Otherwise known as the ideal gas law, Pressure x Volume = moles of gas x R (gas constant) x Temperature.

Say you have a sealed container filled with only CO2, a sealed steel box. As you heat said box, the volume of the gas cannot increase so the pressure inside builds up. If you happened to take up some of that volume in the box with beer, the CO2 in solution would start to come out into the headspace. Cooling it back down would push CO2 back into solution.

Now say this container is a balloon. As you heat the balloon, the volume is allowed to expand, as well the pressure increases. The amount of each of these increases depends on the external atmospheric pressure and the elasticity of the balloon (I'll stick with just theory instead of launching into calculations on this... just for you Revvy ).

Now say this container is your fermentor with an air lock on it. The container is for the most part immovable by the gas expansion. So like the box, as you heat it up you would build pressure inside. BUT, now you've got the variable of the air lock. The air lock has the ability to keep in gas to a certain pressure level, but once that threshold is reached the gas comes spilling out, never to return.

Now I don't doubt that the calculators are close enough for the average brewer, but Revvy... you're not the average brewer. If you were to bottle straight from your cold crash, those calculators cannot apply to. The best bet is to use the temperature that the beer reached at it's highest, so you can accurately measure residual CO2 in the beer. If you fermented in a container with a pressure valve that would keep the pressure inside at, for instance, 10 PSI and then cold crashed and bottled that without ever breaking the seal, then yes you would be wise to use the temperature you are bottling at.

Maybe your original point is right, but that doesn't mean your methodology is.

conpewter said:

I wonder if this would need to take into account the headspace filled with Co2. So if I have beer at 70* with a certain headspace sitting at 1 atm, then move it to the fridge at 40* at 1 atm then it should absorb Co2 (slowly) from the headspace while pulling in air through the airlock (after sucking the water/sanitizer/vodka in). So if I have a huge headspace it should equalize out to having the amount of Co2 in solution that you would expect at 40*, if there was not enough headspace or time, then you'll have less Co2 in solution than you would calculate.

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If you have sucked all of the airlock fluid in and the fermentor is no longer sealed against air flowing in, then you're likely going to end up with little residual CO2 in your beer. The CO2 will escape out to equalise with the air now in the headspace and with air outside the fermentor. If that has happened to you, it'd be best to consider the lowest amount of residual CO2 (likely none if left long enough).

I always disliked not really knowing the actual residual CO2. That is one thing I don't like about a D-rest. The worst thing about bottling cold it the stiff hoses. I just adds a day or two to carbonation.

Given that some of the stuff I wrote is referenced in I may as well chime in and add my 2c worth.

This is a difficult subject and what matters is actually the temp of the beer before bottling. But there are 2 problems: stopped fermentation and CO2 contained in the head space.

Especially w/o doing a fast ferment test and a precision hydrometer it is difficult to asses when fermentation is truly complete. I have noticed gravity drops in ales while it was sitting a cold conditioning temperature of 50F. Granted, I started cold conditioning early b/c I new how much sugar was left in the beer. But I think that you still have enough residual fermentation when you crash to cold conditioning which will create more CO2 that is retained in the beer. If not, you actually have another problem.

If at the start of cold conditioning the beer completely stopped fermenting and no more CO2 is produced, the lowering of the beer temperature and the resulting greater capacity for CO2 will consume some CO2 from the head space. This means that air will be sucked in beyond the extend that can be accounted for by the temperature dependent shrinkage of the head space gas. Now you got air into your head space with the possibility of oxidizing the beer. If we assume that the CO2 lays on the beer like a blanket it offers the beer CO2 at atmospheric pressure and the beer will eventually take up enough of that CO2 blanket to reach the CO2 equilibrium that is shown in the tables and normographs that you mentioned.

In the end it doesn&#8217;t matter what the beer fermented. What matters is the current beer temp.

BUT, you need to keep in mind that the CO2 exchange between beer and environment is a slow process and that those tables are only accurate if the beer sat long enough on its current temperature for the equilibrium to be reached. That means that you can&#8217;t expect the beer to have 1.1 volumes if it has only been sitting at 50F for a day or two. In addition to that active fermentation generally leads to more CO2 in the beer than what is to be expected from the equilibrium equations.

That&#8217;s my take on it. When I prime in the bottle I base the current CO2 content of the beer at the current temp and I also account for the residual amount of fermentable sugars that are still in the beer and the targeted amount of residual sugars. But that latter half is just my geeky self and I don&#8217;t think there are many that do that.

Sorry of I repeated points that have already been made. I skimmed over the posts to try to avoid this.

Kai

If we assume that the CO2 lays on the beer like a blanket it offers the beer CO2 at atmospheric pressure and the beer will eventually take up enough of that CO2 blanket to reach the CO2 equilibrium that is shown in the tables and normographs that you mentioned.

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If I crash in secondary there is (practically) no head space therefore there can not be any C02 added into solution. I've never noticed the gravity change.

Ok, I looked at the existing responses more closely. And until now I didn&#8217;t notice that we are in the science forum.

If we consider a system where air is allowed to be sucked in (carboy w/ airlock) it becomes somewhat complicated. CO2 will be absorbed by the beer but because no pure CO2 is coming in through the airlock the partial pressure of the CO2 will be lowered as it is diluted with air. At some point an equilibrium will be reached with less than the CO2 content than expected from the tables and more than what you would have had at the temp the fermentation stopped at. I don&#8217;t want to do the math for that. I also don&#8217;t think that you&#8217;ll get a nice CO2 blanket since there will be diffusion between the CO2 and the air.

But at this point you allowed air into your head space. What happened to the concerns about oxidation?

As a last point, the pressure created by the water column in an air lock is very small. It is equivalent to an elevation change of about 50ft.

Kai

Kai, thanks for joining this thread. Your added experience is appreciated.

I see two possibilities for this. Cold crashing in the primary or the secondary. For this example we&#8217;ll consider that both were fully fermented before cold crashing and that we are cold crashing an ale from 68 degrees to 35 degrees. In the case of a secondary there is little to no CO2 in the head space to be absorbed, but in the case of a glass primary there may be a gallon of head space. I have cold crashed a lot of beers from the mid 60 degree range and brought them down to the mid 30&#8217;s and never had my airlock sucked completely out. I can see that negative pressure is present, but not enough to pull the fluid through in either a primary or secondary situation. This would indicate to me that very little of the CO2 in the head space has been absorbed and that thermal contraction could account for the negative pressure that I do observe. In the zero to slightly negative pressure environment of the head space, is there enough CO2 present to bring the volumes from the .9 to 1.5 that the chart uses for reference? If so, you say it is a slow process, how long would it take with no new CO2 being introduced?

From what I&#8217;ve observed in kegging, if you charge the headspace with CO2 and remove the gas the pressure in the headspace will drop as the CO2 is absorbed. If the CO2 in the headspace of a carboy is absorbed wouldn&#8217;t a similar drop in headspace pressure occur? Without the introduction of pure CO2 to maintain a constant pressure equilibrium (in this case zero) how would an exchange take place?

As for the scenario where the airlock is sucked out, I would compare that to putting a bottle of beer in the refrigerator opened. Initially the CO2 coming out of suspension will blanket the top of the beer as you describe in the carboy. But in the end we all know that an open beer, even if chilled will go flat.

BUT, you need to keep in mind that the CO2 exchange between beer and environment is a slow process and that those tables are only accurate if the beer sat long enough on its current temperature for the equilibrium to be reached.

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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? I'm not sure, given the chemical complexity of beer, that there is an equation out there that can determine this. It is probably something that needs to be empirically determined. Given sufficient time, then yes, the amount of CO2 in your beer is determined by the current temp of that beer (thanks to Henry's Law). But, as Kaiser mentioned, it won't be at equilibrium after only a couple of days, especially assuming the beer is not being sloshed around or stirred.

here's something I've never seen. A label on volumes of co2. Volumes is almost as good as saying handfuls. What is the unit we're dealing with here? L, cu. ft?

JLem said:

Given sufficient time, then yes, the amount of CO2 in your beer is determined by the current temp of that beer (thanks to Henry's Law). But, as Kaiser mentioned, it won't be at equilibrium after only a couple of days, especially assuming the beer is not being sloshed around or stirred.

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But you also have to take into account available CO2 in the headspace. Temperature doesn't matter one bit if you haven't got he CO2 to absorb in the first place. Equilibrium is also reached much more easily when increasing temperature than lower, it's an entropy thing.

JLem said:

But, as Kaiser mentioned, it won't be at equilibrium after only a couple of days, especially assuming the beer is not being sloshed around or stirred.

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And then the CO2 has to reach an equilibrium within the beer. Keep in mind that there are no currents in beer that is sitting still during cold conditioning. CO2 gets around by diffusing from one spot to another.

This is a very complicated subject and my best advice is to settle on one procedure and adjust your CO2 content target based on previous batches. I myself use a spread sheet to get the right amount of Kraeusen and such for priming but in the end I doubt that I'll be able to tell the difference between 2.2 and 2.4 vol CO2 in the beer.

Kai

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.

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.

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

Tim

JLem said:

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?.

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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.

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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?

AnOldUR said:

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?

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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.

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.

z987k said:

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.

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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.

z987k said:

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

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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

MX1 said:

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.

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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&#8217;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&#8217;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

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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.

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?

Soperbrew said:

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?

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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.