Cold Crashing and Mylar Balloons

[Bigarcherynut]

I have been cold crashing many of my beers for the last couple of years. I have read and tried many tips about helping with dealing with the vacuum that occurs when the fermenter is chilled. I have used cotton balls with Star Stan and Vodka in the airlocks for the most part. The other day I decided to try Mylar balloons like many suggested filled with CO2. I filled 3 balloons and taped a 3" piece of tubing into the balloon and filled them partially with CO2. I plugged those into the hole where the airlock would go. Perfect. Appeared to be the ticket. 3 days later I kegged my beer and after the lids had been removed from the buckets and one from my Fermentasaurus fermenter noticed the balloons were still inflated. I tried to press the gas out only to find it didn't come out. I cut the balloon open to find they have an internal sealing strip inside that seals after filling. Anyone else find this? I'm surprised my Fermentasaurus didn't collapse some due to the vacuum unless it leaked by were the tube went into the airlock. Anyone else find this with Mylar balloons ?

 

[yoop89]

Completely normal. All you have to do is fish a piece of tubing in until you feel it break through that seal. Thats what I use on beers that I cold crash and haven't had a problem. Normally I will fit a TEE between the fermenter, balloon and airlock though and start with an empty, new, balloon and collect CO2 from the ferment.

If you cant get your tubing through try something like a skewer to pierce a few holes in the seal first.

 

[Ogilthorpe2]

https://www.brewhardware.com/product_p/ccguardianv3.htm

 

[Qhrumphf]

The vacuum produced during cold crash is pretty small. Plenty to suck in damaging air, but not enough to collapse a rigid fermenter (unless you're using some particularly flimsy or worn out material I guess...).

 

[Vale71]

The vacuum produced during cold crash is pretty small. Plenty to suck in damaging air, but not enough to collapse a rigid fermenter (unless you're using some particularly flimsy or worn out material I guess...).

The vacuum produced by crashing to near freezing temps can be as strong as -0.4 bar which is more than enough to collapse a plastic fermenter or even a stainless steel one although it will take a few days to get there. The reason most fermenters don't collapse is because they readily let air in long before the vacuum reaches dangerous levels.

 

[Bigarcherynut]

Completely normal. All you have to do is fish a piece of tubing in until you feel it break through that seal. Thats what I use on beers that I cold crash and haven't had a problem. Normally I will fit a TEE between the fermenter, balloon and airlock though and start with an empty, new, balloon and collect CO2 from the ferment.

If you cant get your tubing through try something like a skewer to pierce a few holes in the seal first.

Sounds good, now that I know about the seal. Do you reuse the balloons? Wasn't sure about sanitizing them after being used.

 

[yoop89]

Sounds good, now that I know about the seal. Do you reuse the balloons? Wasn't sure about sanitizing them after being used.

I dont reuse but I dont see any reason not to as long as you dont get any blowoff into the lines or balloon. I just toss and use a new one as I dont cold crash every beer I make.

 

[Qhrumphf]

The vacuum produced by crashing to near freezing temps can be as strong as -0.4 bar which is more than enough to collapse a plastic fermenter or even a stainless steel one although it will take a few days to get there. The reason most fermenters don't collapse is because they readily let air in long before the vacuum reaches dangerous levels.

I can't say I've seen a pressure drop quite that high (but I typically soft crash while spunding before harvesting before full crash so splitting it up is definitely a factor...) but you'd know the math better than I. Otherwise point taken. It's not something I'm keen to take risks experimenting with either way.

 

[Brooothru]

I can't say I've seen a pressure drop quite that high (but I typically soft crash while spunding before harvesting before full crash so splitting it up is definitely a factor...) but you'd know the math better than I. Otherwise point taken. It's not something I'm keen to take risks experimenting with either way.

I just racked to a 5 gal Cornelius keg from a 7 gal unitank after spunding to 1 atm (14.7 psig) @ 68F. After crashing to 35F, the manometer read ~9.0 psig.

Now granted the pressure drop was a combined function of CO2 going into solution as well as contracting with the temperature drop. How much vacuum would it take to structurally deform a tank that is designed to stand up to positive pressure is unknown though I'm sure the engineering data are out there. I've heard anecdotally that pressure vessels can withstand roughly 4 times more positive pressure than negative (vacuum), but I can't cite a reference.

I do use a PRV that also has vacuum relief for excessive negative pressure, but don't know the setpoint relative positive pressure release. For me, one of the value-added benefits of a unitank is the ability to spund and maintain positive pressure during cold crashing in addition to carbonation.

Brooo Brother

 

[Qhrumphf]

The anti-vac PRVs that I use pop at either 1 or 2bar positive (mostly the former but I have used both) and I *think* -0.05 or -0.1bar negative. It's a significant difference in tolerances.

I've never seen a vessel collapse from cold crash even if not under pressure and without anti-vac (though you can hear it suck in heavily as soon as the seal is broken or pressure is applied which even apart from collapse risk is a big enough issue on its own to not do it). Perhaps it wasn't enough time or had enough ingress through seals regardless as Vale suggested. The collapses I've seen are sealing a HOT empty tank before it's cooled, or pumping out of a sealed vessel.

 

[day_trippr]

Obviously, not a "crash-cool" thing, but vacuums can be hella powerful forces.
This was a 3bbl hlt, half filled with boiling water, then left overnight - sealed tight.
Next morning, this is what the crew found...

Cheers! (That definitely is not going to buff right out )

 

[Qhrumphf]

Plenty of photos out there of massive commercial conical fermenters where someone hooked up the transfer pump without adding CO2 pressure to the tank and the antivac (if it had one) couldn't keep up.