Cold crashing

[DVCNick]

I'm sure there are about a million threads on this, but most systems I've ever seen for pre-cold crash C02 capture seems to be some jerry-rigged plastic bag. At least anything that works with a non-pressurized carboy style fermenter. Is there a better way? It would have to fit in my chest freezer ideally, so it will have to be very low profile on the top. Searching for a commercial turnkey solution; nothing seems to be out there either.

 

[Rob2010SS]

There's this method from norcal brewing solutions...

Have this hooked up during fermentation and it'll fill one of the mason jars with co2. When you cold crash, it'll suck that co2 back into the fermenter.

I have this myself but I have yet to use it.

 

[brewswithshoes]

There's this method from norcal brewing solutions...

View attachment 648494

Have this hooked up during fermentation and it'll fill one of the mason jars with co2. When you cold crash, it'll suck that co2 back into the fermenter.

I have this myself but I have yet to use it.

Not knocking this NorCal option as it works well, but if you keg (and/or have an extra keg) you can do the same thing as this harvester pretty simply with some keg connections and tubing. There is a good thread on here about doing it this way. Will see if i can find and post thread link.

I look at NorCals offering, and almost bought it, but instead went with the keg option and it works flawlessly for me for both cold crashing O2 elimination, as well as using that keg for closed transfers.

 

[brewswithshoes]

https://www.homebrewtalk.com/forum/...ransfers-from-fermonster-to-corny-keg.664270/'

Never posted a direct thread link so hope the above works. If it doesn't, the thread is located in the Bottling/Kegging subforum and titled "pressurized transfers from fermonster to corny keg" . There is good info and pics in there on how to accomplish this.

 

[DVCNick]

Good thread there.
Actually right now I have my first Fermentasaurus fermentation going. It is for a wheat beer where I think yeast esters are possibly part of the flavor profile, so haven't let any actual pressure accumulate, but have easily used fermentation gas to liquid purge my two kegs and will also easily do a zero-oxygen cold crash (if wanted on this type of beer) and closed system transfer with it.

For my non pressurizeable BMB's, I guess the only solution really is to attach a balloon to the airlock via a hose so I can lower it to the bottom of my chest freezer. They don't make a non-ported BMB top that I can find, plus they don't thread on, so I doubt I could get enough positive pressure to hold inside to actually be useful for anything at all.

 

[brewswithshoes]

you should be able to attach a tube to a 3 piece airlock connection. then just attach a ball/pin lock connector to the other end to use the keg setup. the setup is not for pressurized fermentation, but more to capture the CO2 gas, then to use that setup for cold crashing so as not to introduce oxygen.

 

[LittleRiver]

...They don't make a non-ported BMB top that I can find, plus they don't thread on, so I doubt I could get enough positive pressure to hold inside to actually be useful for anything at all.

The balloon thing actually works quite well. Your BMB lid will easily hold the tiny amount of pressure needed to inflate the balloon. I do it all the time with my BMB. Don't use an elastic balloon, use a mylar one.

Completely deflate the balloon (roll it up) and put a clamp on the hose going to the balloon. Keep it closed for the first day or two of fermentation. You don't want to collect the air that's in the headspace, give the yeast time to purge it before you open the clamp.

Have a second line (either from the fermenter lid, or from a T in the balloon hose) submerged in some StarSan (a traditional blow off). When the balloon fills, gas will start bubbling out of the StarSan. When you cold crash, gas will be pulled from the balloon because there is less resistance than pulling StarSan through the blow off hose.

A variation is to run the blow off hose to the beer post of a sanitized keg, and put an airlock on the gas post. This way you can purge your keg with fermentation gas. doug293cz's calculations show that there is sufficient volume to purge the keg very effectively. I've been doing this for a while now, and it works well.

 

[DVCNick]

Since the volume of the keg doesn't change like a balloon, if you don't start with significant positive pressure, it seems like you are still going to generate negative pressure while cold crashing, that will suck in air either during the process, or at best when you disconnect the keg..no?

 

[DVCNick]

I guess you could hook the fermenter up to the liquid side and then equalize the pressure with bottle C02 when the time comes.

 

[brewswithshoes]

i think it mentions it in that thread, but what i do when i go to cold crash i switch the post connections so the fermentor is connected to the gas post, then the connection to the liquid/out line goes into a bucket with star san/etc. (should have mentioned above, when fermenting i have the fermentor connected to the liquid/out connection and then the tubing line into the star san is connected to the gas post. Fermenting CO2 off gasses down the dip tube and pushes excess out thru the gas out into the line into star san bucket)

In the cold crash, when the cold starts to pull from the keg (now that the connections are swapped) the back pressure will pull CO2 out of the keg, and the line in the star san bucket will pull up that liquid back into the keg. no harm in that star san getting into the keg as the back pressure will always be pulling from the "higher up" gas post connection.

 

[DVCNick]

Ah. That makes sense. Thanks!

 

[LittleRiver]

Since the volume of the keg doesn't change like a balloon, if you don't start with significant positive pressure, it seems like you are still going to generate negative pressure while cold crashing, that will suck in air either during the process, or at best when you disconnect the keg..no?

Yep. To me a balloon is the right tool for the job. It's simple and very effective.