[Kaiser]

I remember discussing a similar subject before on another board. The main topic was if the CO2 content that should be considered for bottling needs to be calculated with the temp at which the beer stopped fermenting or the current beer temp. My argument was that cooling the beer will allow more CO2 to be absorbed which will come from the headspace. Another user mentioned that be barely sees the airlock water level move when he crashes his beers.

Aside from that I still think that the beer will suck in CO2 from the head space if it is done fermenting and cooled considerably. There is more room for CO2 in the beer at colder temps and it needs to be filled. I don’t know how long it would take though but am concerned that a considerable amount of air would be pulled in.

So I ran a quick calculation of the problem. I assume that there are 20 l of beer with a 2 l head space. It is sitting at 20 C (68 F) and is at equilibrium with the head space CO2. That headspace CO2 is at atmospheric pressure (~100 kPa). No more CO2 is produced by the fermentation. Now the beer is chilled to 0 C (32 F). Since the beer can absorb more CO2 it will do that. As I mentioned earlier it will pull in air and dilute the CO2 which lowers the CO2 head pressure. Once that CO2 head pressure has fallen to about 55 kPa, which corresponds to a head space CO2 content of 55%, the 0 C beer CO2 content will be at equilibrium with the head space again. As a result about 65% of 2 l = 1.3 l air must have been pulled in through the airlock.

2 l head space might be a bit generous for a secondary. If you have only a pint (500 ml) you will pull in only 325 ml ( ~0.3 qt) of air. I’m not sure if that is enough to cause considerable oxidation since a lot of brewers are doing exactly that w/o apparent stability problems. If I go a bit further and make the assumption that the 20 C beer may be oversaturated with CO2 (i.e. holds more CO2 that what it should be able to hold at its pressure and temp) it would have to hold almost twice as much CO2 in order to prevent air from being sucked into the head space while and after chilling to 0 F.

If the beer is only chilled to 10 C (50F) only 25% of the head space will be replaced with air.

These calculations neglect the temperature dependent contraction of the head space volume which only makes the problem worse.

In Keith’s case the airlock ran dry which allowed much more air to diffuse into the head space.

For those who cold crash beer in a secondary, do you see negative pressure on the airlock to the extend that air is pulled in? Or do you see CO2 escape from the beer. The latter can be evident by the formation of bubbles on the surface.

Kai

[bluesman]

I recently made a Boston Lager clone. I brewed the beer and chilled it down to about 60F then transfered it into a  (2) 7.5 gallon buckets which were then transferred into my chest freezer controlled by a  Johnson controller set at 50F.

I leave the airlocks off because if I don't, the cooling of the air in the headspace will cause the air to contract which will in turn suck the liquid out of the airlocks and into the beer. So it's a tradeoff between sucking the liquid from the airlocks into the beer or sucking more O2 into the headspace which will then oxidize the beer.

Once the beer gets down to pitching temp, I install the airlocks. That usually takes about 4-6 hours or so in my chest freezer.

[tygo]

In that case though it shouldn't really matter since that was your primary fermentation though.  You wouldn't need to worry about oxidizing the beer at that point.  The tricky part seems to me dropping the beer to lagering temperatures from fermentation temps if you're using a carboy with an airlock as opposed to a keg under pressure.

[bluesman]

In that case though it shouldn't really matter since that was your primary fermentation though.  You wouldn't need to worry about oxidizing the beer at that point.  The tricky part seems to me dropping the beer to lagering temperatures from fermentation temps if you're using a carboy with an airlock as opposed to a keg under pressure.

Yes, assuming that the yeast will chew up all of the available O2 during the fermentation process. I typically lager in a keg with the exception of a Dopplebock or the like which then presents the same issue.

The best way to avoid this issue is to secondary and/or lager in the keg.

[Kaiser]

If you want to get serious about lagers, I recommend working with kegs. I’ve started using them to cold condition my lagers way before I even had a keg-o-rator.

Kai

[blatz]

If you want to get serious about lagers, I recommend working with kegs.

+1 - problem solved.

[majorvices]

+2 - in fact, if you really want to get serious about beer I recommend kegs. 

[ndcube]

+2 - in fact, if you really want to get serious about beer I recommend kegs. 

Kegs are next on my list.  For now I'm using carboys.  If I ever need another carboy the money will most likely be spent on a keg instead.

[blatz]

Kegs are next on my list.  For now I'm using carboys.  If I ever need another carboy the money will most likely be spent on a keg instead.

don't know if you got an extra benjamin burning a hole, but NB has/had a pretty good sale going on - 4 for $115 I think?

[troy4500]

For those who cold crash beer in a secondary, do you see negative pressure on the airlock to the extend that air is pulled in?

Kai

I see this everytime I cold crash.  wheter in the primary or secondary carboy.  This is something I have alway wondered about.  I have always read about people opting to cold crash in the primary then keg or bottle to avoid O2, but I always have a negitave pressure occur and have wondered how that is any different.  That being said, I secondary alot of my beers and have never had an oxidation issue, though I am now doing secondary and cold crashing in the keg.

[Thirsty_Monk]

Kegs are next on my list.  For now I'm using carboys.  If I ever need another carboy the money will most likely be spent on a keg instead.

don't know if you got an extra benjamin burning a hole, but NB has/had a pretty good sale going on - 4 for $115 I think?

I have a guy in club who is selling them for $10 a piece.
You just have to drive to his farm.
They are not recondition and he has like 300 of them (at least that is the claim).

[ndcube]

Kegs are next on my list.  For now I'm using carboys.  If I ever need another carboy the money will most likely be spent on a keg instead.

don't know if you got an extra benjamin burning a hole, but NB has/had a pretty good sale going on - 4 for $115 I think?

Looks like it's part of their $8 shipping too.  I've seen them cheaper on other sites but shipping is like $40.  I just put in an NB order or I may have done that.  'Course then one needs all the accesories too...  then I'd want to build a kegerator (which isn't allowed in the kitcehn for some reason)... buy even more kegs...  think I'll stick with what I've got for a few more months.

[dean]

I've got ten cornies and have yet to have them all filled at the same time, so using them as secondaries sounds like a really good idea.  Would I need to cut the dip tube, how much sediment typically settles out doing a secondary?

Keith... you should know some of us just like fun with ya when we get the opportunity.   

[Thirsty_Monk]

I've got ten cornies and have yet to have them all filled at the same time, so using them as secondaries sounds like a really good idea.  Would I need to cut the dip tube, how much sediment typically settles out doing a secondary?

Keith... you should know some of us just like fun with ya when we get the opportunity.   

I have two kegs with dip tub cut.
If you do that you can cut 1/2 inch off.
I use them as a clear tanks.
I rack beer from fermenter to these kegs.
Cold condition it for 2 weeks and I transfer it to serving keg.
IMO It is worth the effort.

[bluesman]

This is the thread that just keeps going...and going...and going. I love it.