Cold Crashing. is it worth the risk with hoppy beers?

[doug293cz]

Ok, here is my situation: I am brewing an IPA (brewed on April 19th). Fermentation done since almost a week, beer still sitting in the primary ( I don't do secondary). First time I have temp control: sat around 65-66 until towards the end of fermentation, and ramped up to around 70.

I dry hopped yesterday. I want to try short dry hop (48-72 hours), and I pretty much have to bottle on Sunday evening (for some other reasons). Because of all the hop in suspension, I wanted to cold crash before (especially since I now can).

It's a 4-gallon batch in a 6-gallon plastic carboy, so plenty of headspace... And I only have a 3-piece airlock. I am afraid that the air compression will suck back the Star San (that doesn't concern me too much), and lead the carboy to "implode" since it's plastic and there is quite a lof of headspace.

My plan is to remove the airlock and put a sanitized foil with a rubber band... I know I risk some oxidation, but I don't know what else to do (I don't have CO2 setup).

Any thoughts?

You will get air in the carboy whether you use an airlock or foil. Just the act of removing the airlock and replacing with foil will allow the foil method to get more air into the carboy. An airlock will not support a high enough pressure differential to cause a plastic carboy to collapse.

A 3-piece airlock will suck back at most 10 ml of liquid (a little more than 1/3 fl oz) when filled to the top "Fill Level" line (yes, I measured.)

Brew on

 

[derekcw83]

Based on an earlier post by someone, it looks like you might only pull in a pint or so of air, so maybe worth looking into trying to setup a very long, wide hose and sanitizer container, set way below your level of fermenter. Gravity will help fight it. I intend to try this on my next batch. But I'm going to attach this long hose and container at least a few days before to let co2 to build up in the hose.

 

[doug293cz]

Based on an earlier post by someone, it looks like you might only pull in a pint or so of air, so maybe worth looking into trying to setup a very long, wide hose and sanitizer container, set way below your level of fermenter. Gravity will help fight it. I intend to try this on my next batch. But I'm going to attach this long hose and container at least a few days before to let co2 to build up in the hose.

I did the pint calculation.

Your plan will work as long as you don't have leaks elsewhere in you system. Your arrangement will set up a small negative pressure in the fermenter, so if there are leaks, air will get in.

Brew on

 

[zippybasher]

fwiw
- I cold-crash everything but my porters and stouts.
- An s-lock will not allow liquid to "suck back".
- It will, however, still allow air to enter the FV.
- If you want to avoid that, you could do something like this...

View attachment 352110

Cheers!

WHAT if you inflated the balloon with co2 and stuck it over the top of the carboy or on the end of the blowoff tube... Wouldn't need to have co2 hooked up at all during crashing. the balloon would just shrink... way simpler. :rockin:

 

[FreddyMar3]

I use those Mylar baloons. They'll hold the CO2 for a long time and don't get weird/shrink in the cold fridge. I just pump them up with my tank and slip tube in that connects to the bung.

 

[day_trippr]

WHAT if you inflated the balloon with co2 and stuck it over the top of the carboy or on the end of the blowoff tube... Wouldn't need to have co2 hooked up at all during crashing. the balloon would just shrink... way simpler. :rockin:

Yeah....no. Unless you have huge balloons and the space to inflate them.

I tried that once - by filling the balloons until they were almost touching the fridge "ceiling", then shutting off the gas, and starting the crash.

It turns out the CO2 volume needed is not only to make up for the volumetric shrinkage of the FV contents (head space and fluid combined) during the temperature transition. It also has to handle the CO2 absorption into the beer - the rate of which increases as the temperature drops.

I set the system up as described above, and by the next morning both balloons were totally flat and partially sucked into the carboy cap ports. And at that, the beer temperature had only dropped half way from ~68°F to the target 34°F (that's expected - it takes nearly 36 hours for that fridge to drop ~11 gallons of beer ~34 degrees).

So if you're going to crash for a few days, you'll be refilling those balloons a couple of times a day, guaranteed. Which belies the "fill the balloon" approach as being superior to the "just leave the gas connected" method, imo...

fwiw, the CO2/beer interface of a 6.5g Italian glass carboy with ~5.5 gallons in it is roughly 105 square inches, verses a ball lock cornelius keg's 53...

Cheers!

 

[doug293cz]

Yeah....no. Unless you have huge balloons and the space to inflate them.

I tried that once - by filling the balloons until they were almost touching the fridge "ceiling", then shutting off the gas, and starting the crash.

It turns out the CO2 volume needed is not only to make up for the volumetric shrinkage of the FV contents (head space and fluid combined) during the temperature transition. It also has to handle the CO2 absorption into the beer - the rate of which increases as the temperature drops.

I set the system up as described above, and by the next morning both balloons were totally flat and partially sucked into the carboy cap ports. And at that, the beer temperature had only dropped half way from ~68°F to the target 34°F (that's expected - it takes nearly 36 hours for that fridge to drop ~11 gallons of beer ~34 degrees).

So if you're going to crash for a few days, you'll be refilling those balloons a couple of times a day, guaranteed. Which belies the "fill the balloon" approach as being superior to the "just leave the gas connected" method, imo...

fwiw, the CO2/beer interface of a 6.5g Italian glass carboy with ~5.5 gallons in it is roughly 105 square inches, verses a ball lock cornelius keg's 53...

Cheers!

Thanks for that info @day_trippr . I left the part about absorption of CO2 by the beer at lower temps out of my response because I didn't think it would happen that fast. I will need to look into this further.

Brew on

 

[brick_haus]

I agree, constant positive co2 pressure is the solution to preventing oxidation during cold crashing and transferring. The method doesn't matter. Having a co2 bottle and regulator is a necessary investment if you brew hoppy beers (IMHO).

 

[derekcw83]

So far so good. I tried the long blow off tube attempt today. 1 gallon carboy has taken in nearly 7 feet of sanitized water into a 3/8" tube, but I feel confident I have avoided oxygen getting into the system. A few days before I dry hopped and attached the long blow off tube in order to "purge" it with co2. It should be nearly down into the 30's by now and liguid movement into the blow off tube has slowed dramatically. Hopefully getting to botle tomorrow or the next day and have some results in a few weeks.