amount of sugar after cold crashing?

I am confused at which temperature i should use to calculate the residual co2 in my beer. I fermented the beer at 68 for 3 weeks and then crash cooled to 37-40. I plan on bottling later this evening and took the beer out of the fridge to its final siphoning location earlier today. The beer has been slowly rising in temperature and now it is at ~50. Should i put my beer temperature at 68? or 50? I would thing all of the co2 went out of solution at the higher temp, and there would be no way for this co2 to go back into solution as it escaped out of the air lock.

There really isn't any residual co2 to take into account when cold crashing. Just prime as normal. Is that what you're wondering?

PT Ray said:

There really isn't any residual co2 to take into account when cold crashing. Just prime as normal. Is that what you're wondering?

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no, you put in the temperature of your beer and that then determines the weight of sugar to put into the beer

I've seen charts giving the volume of co2 produced with each ounce of priming sugar used but none that takes temperature into account. There are charts for force carbing that will give the volume of co2 that will be dissolved based on pressure and temperature.

Use 68

In general, you should use the highest temperature it sat at after fermentation was complete. After fermentation, no more CO2 is being produced, so no more can be dissolved into the beer, but you can lose dissolved CO2 when the temperature rises. Dropping the temp will simply keep what is already in it.

PT Ray said:

I've seen charts giving the volume of co2 produced with each ounce of priming sugar used but none that takes temperature into account. <snip>

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How about this one?


As was mentioned by earlytimes, it's the highest temperature the beer has been subjected since the completion of fermentation.

The effects of cold crashing on priming sugar needs

Perhaps this thread can provide more insight.

I retract everything said. That's something I would have just left alone for someone else.

Oh I can't resist after reading the debate. I can't help but laugh.

I think the BYO article covers the residual carbonation issue perfectly. It simply states after fermentation at a given temp. you can expect (in theory) this amount of residual co2. Everything you do after that such as racking or changing the temp will affect how well it holds that gas. Does t his really have any merit? For me, show me a study where the beer was fermented at 68 degrees, racked to a bottling bucket and bottled. Then give me the measurement of co2 that actually made it to the bottle.

Now, for the Nomograph. The only sense I can make out of it is that it pertains to serving temps. I don't care what temp you use to bottle, if you take two solutions that have been degassed, bottled at two different temps with the same amount of prime and then allowed to condition, they both will have the same volume of co2 in the bottle. If you store them at two different temps before serving, the two solutions will hold two different amounts of gas. For the one that is warmer to equal the colder one you would have had to prime at a higher dosage. Thus where the Nomograph comes in.

Now I'm done. Nah, never been one to leave well enough alone.

PT Ray said:

<snip> Everything you do after that such as racking or changing the temp will affect how well it holds that gas. Does t his really have any merit? For me, show me a study where the beer was fermented at 68 degrees, racked to a bottling bucket and bottled. Then give me the measurement of co2 that actually made it to the bottle. <snip>

I am with you here. Any transferring of the beer while open to atmosphere will cause some change in the concentration of C02 in solution. Unless of course the partial pressure of C02 over the beer is equal to or at a higher pressure than is required to maintain the current C02 concentration in solution. These two options only come into play when doing pressurized transfer with C02. As for empirical data, I would be curious to this as well. Now the trick is convincing someone with access to a gas chromatgraph to sample the head gas to determine the partial pressure of C02 after each transfer.

<snip> I don't care what temp you use to bottle, if you take two solutions that have been degassed, bottled at two different temps with the same amount of prime and then allowed to condition, they both will have the same volume of co2 in the bottle. If you store them at two different temps before serving, the two solutions will hold two different amounts of gas.<snip>
<snip>

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For completely degassed solutions, I agree. Are you working on the assumption that racking to a bottling bucket would completely degas the beer? Traditional methods to completely degas a solution involve either 1) boiling, or 2) repeated freeze/pump/thaw cycles. Alternatively, whatever residual gas is dissolved in the solution can be displaced by 3) continously bubbling a pure gas through the solution (nitrogen, argon, helium). Given the care most people take in racking their beer to avoid oxidation, I don't see how the beer is becoming degassed by racking.

Now let's consider another option, instead of degassing the beer, the gases in solution are equilibrating with the atmosphere in your bottling bucket. Assuming that reaching equilibrium is a kinetically very fast (i.e. faster than completely filling the bucket), then every time a bottling bucket is used the beer would contain an amount of oxygen determined by the partial pressure and temperature of the solution. If we accept the hypothesis that the entire solution is completely equilibrated with the atmospheric mixture of gases upon transferring, you would have incorporated oxygen into your beer. Wouldn't this lead to oxidation and the subsequent off flavors anytime someone used a bottling bucket?

The Nomograph can be related to serving temps, but it's purpose is meant to account for residual C02 in solution. We can agree, I hope, that fermentation creates C02. Under typical fermenation conditions (carboy, airlock, 65F) the beer is exposed to 1 atm of 100% carbon dioxide, naturally the gas dissolved in solution would equilibrate with the headspace in your carboy. Now the question becomes how much C02 is dissolved in your beer, which can be answered by the nomograph. Assuming a closed system, the amount of C02 in solution depends only the current temperature.

Once the system is opened (i.e. racking to a bottling bucket), another variable has been introduced, the equilibration of the dissolved gases with the atmosphere. While the process will lead to some reduction in the carbon dioxide concentration in the beer, the standard practices employed in racking (minimize splashing, cover the bottling bucket, etc.) reduce the rate at which the gases can equilibrate (agitation) and increase the partial pressure of CO2 above that present in the atmosphere (covering the bottling bucket). These two factors limit the amount of residual CO2 that will be eliminated.

tl;dr
-Fermentation dissolves CO2 in solution
-Standard transferring techniques limit the potential for off-gassing of CO2
-Residual CO2 remains in solution at bottling
-A reasonable approximation of CO2 concentration can be obtained by accounting for the highest temperature the beer was exposed after the beer was exposed to atmosphere (i.e. commonly at bottling).