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Old 08-29-2009, 01:26 PM   #1
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Default 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?

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Originally Posted by Revvy View Post
...but really, if you want it carbed "right" then let the beer warm back up...
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. . . if the beer changes temps (which it does) it lets go or absorbs more co2.
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Originally Posted by greenbirds View Post
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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Old 08-29-2009, 01:54 PM   #2
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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...

Quote:
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.
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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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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.
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.

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Old 08-30-2009, 05:42 PM   #3
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Quote:
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.
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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Old 08-30-2009, 06:04 PM   #4
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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.

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Old 08-30-2009, 06:28 PM   #5
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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).

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Old 08-31-2009, 12:59 AM   #6
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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.

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Old 08-31-2009, 02:05 AM   #7
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Originally Posted by JLem View Post
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 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?
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Old 08-31-2009, 02:55 AM   #8
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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?
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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Old 08-31-2009, 03:24 AM   #9
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The thermal contraction from cold crashing has created a negitive pressure in the carboy, so even the head space CO2 will not be absorbed.
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.
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Old 08-31-2009, 04:16 AM   #10
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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.
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.
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