Cold crashing and keeping oxygen out

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TrojanAnteater

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I was wondering what you all do when cold crashing a carboy, do you leave the airlock on? The one time I did that it sucked the vodka from the airlock into the carboy. I'm not tooooo worried about that addition, but if there's no fluid in there then wont oxygen be able to pass in and out of the carboy?

On my last pale ale batch I took the airlock off and put a couple layers of Aluminum foil over the top and rubber banded it around the neck so it was tight. But is Aluminum foil permeable to air? I'm wondering now because when I bottled the batch it didn't smell hoppy at ALL, and I had dry hopped the sucker with 2 oz of hops (centennial and ahtanum) in a 2.5 gallon batch.

So any takes on the airlock and the aluminum foil, or suggestions on how I go about this next time?
 
I remove the air lock altogether prior to cold crashing or lagering. I use a carboy cap and simply put the small caps on the nipples to keep the air out. A slight vacuum forms in the carboy as it cools, but that hasn't caused any problems that I can detect. I did use one of the "S" shaped airlocks for awhile. Those work in both directions, but they still permit air to infiltrate and that's never a good thing, so I abandoned that practice. Some plastic wrap and a rubber band would probably work as well as a capped cap. The foil should work as well, but I have not tried it.
 
I read this guy Diacetyl-Fermented-Foods-Beverages-Takashi. It says to completely cap/seal off the container that the beer is in (carboy) during the diacetyl and crash cooling.

+1 on the rubberbands and plastic wrap. But even if some air does get in the CO2 in the head space will become intensely more dense during the cooling and will keep and O2 away from your beer. So dont worry. Its not the end of the world.
 
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I always have a CO2 tank close so let it do whatever suckback it likes then re-flood the top of the carboy with gas.
 
thanks for the input fellas. I think the best/easiest way to go is just get a bung/stopper for the top, although ppl seems to think foil is a good option so...
 
What I have done is to make a bag using my Food Saver. I cut an 18 inch length from an 11 inch wide Food Saver roll and sealed one end. Then I made a small hole in one corner of the sealed end and inserted the end of a 1/4 inch vinyl tube, securing it with DAP Household Adhesive Sealant (100% Silicone) from Lowe's. After the adhesive cured, I sealed up the other end of the bag. I put a barb-to-barb adapter on the end of the tube to connect it to my CO2 supply, with a clamp on the tube, near the barb adapter. I turn the CO2 pressure down very low (1 or 2 PSI), connect the bag to the CO2, and begin to fill the bag slowly. When the bag is nearly full (don't fill it too full, or it may pop; also you don't want the bag to be pressurized) I close the clamp on the tube, put the tube onto my carboy cap, and release the clamp. As the wort and air in the carboy cool, only CO2 from the bag is sucked into the carboy. It was really easy to build this and, of course, it is reusable.
 
These are all good ideas, but that does not solve the OP's problem. The SLIGHT amount of oxygen entering a carboy will not show up as oxidation for weeks/months and would not mask high rates of dry-hopping.

TrojanAnteater - how long did you dryhop for? What recipe? Fresh hops?
 
It was a pale ale about 5.8% using centennial and ahtanum in about equal amounts. 2.5 gallon batch, used 4oz of hops total (2oz of dry hopping). They were fresh, got them at ballast point homebrew Mart. Dry hopped it for about 7 days, then cold crashed for 4 total adding the gelatin in after about 36 hrs in the cold. So yeah it was in the fridge for 4 days with that foil rubber banded on it. I really just wanna he sure that it can "breath" at all while doing that... Don't want to have fridge air moving in and out and whatnot. Only reason I cold crashed in this state was because I was trying gelatin for the first time and read it worked a bit better after cold crashing first. Bottles have been carbing for a week I should pop one open tonight and check on the smell/taste.
 
Well I must say I don't think the foil over the carboy while cold crashing affected much, beer turned out pretty good!
 
It is always amazing how different it tastes when bottling vs. after fully carbonated. Cheers!!
 
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