Avoiding O2 uptake while crash-cooling fermenter

[bwarbiany]

Planning on kegging my IPA towards the end of the week. For clarity, i usually prefer to add gelatin to the fermenter and crash-cool for several days before transfer.

Setup:
1) Brewer's Hardware Sanke keg conversion as a fermenter. Racking cane is *nearly* airtight, as I have used a thicker o-ring to seal the compression fitting.
2) Blowoff tube from the fermenter sits in a plastic cup with sanitizing solution. Tube is fitted with a threaded barb to mate with output of CO2 tank.

As you can imagine, crash cooling from ~70 deg to ~40 deg F causes a negative pressure inside the fermenter, which will suck up my sanitizing solution to the point of ingesting untreated air into the fermenter if I let it. Alternatively I can loosen the clamp on top of the Sanke kit, but all that does is allow the untreated air to pass in through the neck of the fermenter -- still not optimal.

So my proposed solution is to hook up my CO2 tank to the blowoff tube during crash-cooling [which is actually the same configuration I use for forced transfer to serving kegs], with the valves open and the gauge screw turned *JUST* enough that the pressure needle on the gauge comes off its 0 psi rest. I assume that at this extreme minimal pressure, I have no chance of forcing the beer out of the racking tube -- but the last thing I want is to find 10 gallons of IPA on my garage floor one morning...

Does this seem like a decent solution? Any differing suggestions?

[JonW]

Your CO2 will run empty in no time doing it that way.

I just pull the blowoff tube from my jug and put foil over it to keep any bugs or nasties out. I don't worry about any O2 in the beer since the sanke is already filled with CO2 and any O2 being pulled in is going to be at the top of the vessel. Since CO2 is heavier, I feel that there is always a blanket of it covering the beer from any O2 that may be in the head space.

That's my logic and I'm sticking to it!

[backyard brewer]

I've thought about this in the past but never did much with it. My concern wasn't on the initial pull down since I do what Jon does and the wort was just exposed to that same air in my kettle anyway.

I thought about using an old scuba second stage and hooking it up after a primary CO2 reg. They are balanced to ambient and only flow on demand and to demand so if you had a tube running from your sealed fermenter to the mouth piece of the reg, it would flow anytime the pressure dropped in the fermenter relative to ambient. I always though it would be a cool device to prevent air from entering when taking samples from beers you want sitting around for a while and near the end of fermentation when there isn't much CO2 being made. I also don't think it's a big enough issue to spend a whole lot of time with. It just kinda crossed my mind one day while I was diving...

[backyard brewer]

Oh and I should add that I had a customer use an airlock instead of the blow off setup for primary once. The airlock plugged with kreusen and fermentation generated enough pressure to pump all 10 gallons on the floor so I DONT recommend that.... If you're going to blow a little CO2 into the fermenter do it through the racking cane.

[brahn]

I've thought about this in the past but never did much with it. My concern wasn't on the initial pull down since I do what Jon does and the wort was just exposed to that same air in my kettle anyway.

I think he's talking about post-fermentation, so it wouldn't have been exposed to any air in the kettle recently. Still, I agree with Jon that it's not really an issue. So far I don't have the ability to crash cool in the fermenter, so I don't have this problem.

Oh and I should add that I had a customer use an airlock instead of the blow off setup for primary once. The airlock plugged with kreusen and fermentation generated enough pressure to pump all 10 gallons on the floor so I DONT recommend that....

That really surprises me! I've only used a blowoff tube, but I've never seen any krausen make it up to the blowoff tube. I ferment between 11-12 gallons, enough to fill 2 corny's with a gallon or so left over. I don't think you could get enough in the fermenter to fill 3 corny's so I'm not sure why you'd do much more than that...

[bwarbiany]

Well, now you guys are making me feel like I'm overly paranoid. So I guess I might just remove the clamp on the top of the fermenter and allow the little bit of O2 that enters to enter... The O-ring under that clamp should be enough to keep out any living motive stuff...

[maltbarley]

You can always use an "S" airlock with vodka. It won't take out the oxygen, but it will clean the oxygen that makes its way in there.