Cold Crash Question

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dan46nbrew

dan46nbrew

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I have a Spike conical fermenter with a blow off tube going into star san. I was wondering if I can seal off the blowoff tube when I start to cold crash so it doesn't suck the star san back up? I'm a little confused though because on Spikes website they recommend pressurizing the conical to 5 PSI which you would have to seal off the fermentor doing that anyway. So I don't see the point of pressuring it when you can just seal it off?

https://cdn.shopify.com/s/files/1/0...c80-9d3d-9a95ac550b96.pdf?4228242542540715570
 
So, to simplify a bit, when you cold crash...the gas volume in the fermentor drops creating negative pressure. The lower temp allows more CO2 to be absorbed into the beer, also creating negative pressure. If you don't do something to mitigate air/starsan inflow then air (O2!) will be sucked in after all the starsan in your airlock/blowoff tube has been sucked into your beer. The options are: change the blowoff to a balloon filled with CO2, pressurize your fermentor with CO2 to offset that negative pressure, seal your fermentor before FG (creating positive pressure), or accept the vacuum and with the first opportunity air will be sucked in to fill that negative pressure (O2!). Oxygen is the enemy of quality beer :) .

With your awesome Spike conical...simply seal after fermentation is complete, pressurize with CO2 (5psi is a good estimate) and cold crash with impunity :).
 
Moreover, if you close it off, not allowing gas to get in when the temp drops, the "negative pressure" inside the fermenter will eventually implode it!

Pre-pressurizing with CO2 or using an expansion balloon with CO2 are 2 methods to help prevent such disaster from happening.
 
i pressurized my milk can to 5 psi with a blow off tube....and being i have no way to pressure "transfer" i was worried about foam pumping it, so pulled to gauge, and i'm pretty sure it was a bubbling in my water for quite some time letting off that 5psi....i'm assuming this has some sorta spunding type thing to get your 5 psi?


looking at a carb chart, chilling 5 gallons from 65f, to 38f...you'd still have 4 psi in it? so no suck back from the spunding thingy?

(just tossing an idea out)
 
I didn't think about the implosion possibility. Ended up sealing the blowoff and pressuring to 5PSI and waiting for the chiller to do its thing. Thanks for the explanations!
 
and honestly, not like a warm beer can "implodes" when you throw them in the fridge, and i'm sure that's got thiner mettle....
 
Bobby_M said:
Warm canned beer has 25psi. Cold beer has 10psi, those are both at least 10 psi away from vacuum.
Click to expand...

but like the psi difference if i'm lookiing at the carb chart right is 1psi between 95f, and 38f? and i doubt 1mm or better is going to implode? if a plastic bag can handle vacuum sealing, seriously...worry about a SS conical fermenter turning into a crushed can???? (because you put it in the refrigerator? come on?)

edit: you could put a conical in a chest freezer...without a temp controller...and still have more to worry about the water expanding then contracting....:mug: gotta cover the pipe in winter....no fear of them shirking on me! lol)

edit: that meant to say 65f....not sure if it matters...
 
Last edited:
bracconiere said:
but like the psi difference if i'm lookiing at the carb chart right is 1psi between 95f, and 38f? and i doubt 1mm or better is going to implode?
Click to expand...

I don't know what chart you're looking at, but the difference is much greater than 1 PSI. Let's say a container of beer (ignoring headspace for simplicity) starts off at 0.8 volumes (approx residual CO2), at 95F. That would be at about 9.4 PSIG. Chill that to 38F and you're at about -6.8 PSIG. Note the negative PSIG. Would that be enough for a typical homebrew conical to buckle? I dunno. But at the very least, it's going to suck in air quite vigorously when opened. And that's assuming the negative pressure hasn't resulted in air being sucked through imperfect seals in the meantime.

bracconiere said:
if a plastic bag can handle vacuum sealing, seriously...
Click to expand...

You really can't compare the two. The plastic bag is flexible. Or put another way, the vacuum sealed bag has been crushed, as intended.

bracconiere said:
worry about a SS conical fermenter turning into a crushed can????
Click to expand...

The reason the beer can doesn't crush is that it's starting out at (say) 2.5 volumes of CO2. In your example, that would be at about 44.2 PSIG at 95F. Chill that to 38F and you're at about 11.2 PSIG. Note that it's still at positive pressure relative to the outside pressure.
 
dan46nbrew said:
I have a Spike conical fermenter with a blow off tube going into star san. I was wondering if I can seal off the blowoff tube when I start to cold crash so it doesn't suck the star san back up? I'm a little confused though because on Spikes website they recommend pressurizing the conical to 5 PSI which you would have to seal off the fermentor doing that anyway. So I don't see the point of pressuring it when you can just seal it off?

https://cdn.shopify.com/s/files/1/0...c80-9d3d-9a95ac550b96.pdf?4228242542540715570
Click to expand...
I have one of these Spunding Valve. I pressure ferment @ 8 lbs. When cold crashing, I put the gas on @ 3-5 lbs. to add co2 should the "shrinkage" displace the 8 lbs. of pressure already in the conical.
 
bracconiere said:
but like the psi difference if i'm lookiing at the carb chart right is 1psi between 95f, and 38f? and i doubt 1mm or better is going to implode? if a plastic bag can handle vacuum sealing, seriously...worry about a SS conical fermenter turning into a crushed can???? (because you put it in the refrigerator? come on?)

edit: you could put a conical in a chest frezer...without a temp controler...and still have more to worry about the water expanding then contracting....:mug: gotta cover the pipe in winter....no fear of them shirking on me! lol)
Click to expand...

I'm not trying to mean but a high school level physics 1 text book would be a very enlightening and interesting read. Hydraulics and other pressure related topics often contradict ill- applied common sense. You hit on a lot of them.

Insulating a pipe? The pressure into the pipe is constant typically from a water tower until it freezes and expands.

A vac bag IS imploding on purpose until the rigid contents stop it.

Canned beer is always under pressure no matter what temp. Beer fermenting with no spunding or back pressure is going to be pretty close to atmospheric pressure.and therefore close to going to vacuum. Fill a soda bottle half way with Luke warm water and put it in the fridge. Are the sides still round?

The cone and domed lid have no problem. Its the vertical walls most subject to denting inward. When you spend $800 on a fermenter and ruin it, that's a hard lesson.

I don't have time to find the thread but someone imploded their brewha BIAC jacketed conical to the tune of $1600 or so. Granted the temp change was more extreme.
 
bracconiere said:
...worry about a SS conical fermenter turning into a crushed can???? (because you put it in the refrigerator? come on?)
Click to expand...
Yes it can happen. Vacuum is powerful and it doesn't take much. I know the temp swing is much diff, but many moonshine stills have suffered the crunch
 
If you just seal off the tube, then you will have lower pressure inside the fermenter as it cools. How much? I'll let the math and physics people work that out.

The few times I've cold crashed, I just took a balloon, sanitized it, then pushed the balloon through the hole of a sanitized stopper and then stretched the opening of the balloon over the stopper. Then I quickly swapped that out for the stopper with the blow off tube. And added some electrical tape to keep the lip of the balloon secured to the rim of the stopper. Though probably not needed since my stoppers have a large taper to them.

Depending on the amount of headspace, the balloon might fill up some inside the fermenter or just barely fill to hang limp in it.

While it's true air and o2 permeate through latex, it's probably not much and better than doing nothing.
 
Bobby_M said:
I would go for not cold crashing over using a latex balloon. A stretched balloon is very O2 permeable.
Click to expand...
I currently don't care to cold crash. I didn't get any benefits from cold crashing of the two beers I did that for. And I don't need to clarify my beers as they come out pretty clean. My IPA's are so clean they might not have enough haze to them if they were judged.
 
Bobby_M said:
Fill a soda bottle half way with Luke warm water and put it in the fridge. Are the sides still round?
Click to expand...

LOL, yeah it will dent inward...but it's elastic...i can feel how flimsy it is with my hand....

Bobby_M said:
I'm not trying to mean but a high school level physics 1 text book would be a very enlightening and interesting read.
Click to expand...

yeah it would be, and don't pull punches...i'm interested...but i know in a glass jar i can pull 25-30psi vacuum, when i'm filtering something, and it doesn't implode!


and i think i noticed a typo, it was meant to read 65f->38f......(and i just thought about canning, why don't all the mason jars implode?)

edit: now i'm thinking how they could ever perfect the canning proccess with cans?
 
Last edited:
bracconiere said:
but i know in a glass jar i can pull 25-30psi vacuum, when i'm filtering something, and it doesn't implode!
Click to expand...
You can only "pull" 14.7 psi in a vacuum, as that's the pressure of the surrounding atmosphere, at sea level.
At 6000 ft elevation about 80% of that, 11.8 psi.

Mason jars can probably sustain that pressure from the outside (vacuum inside). I'm not sure if it holds when the same pressure is applied from the inside.
 
IslandLizard said:
You can only "pull" 14.7 psi in a vacuum, as that's the pressure of the surrounding atmosphere, at sea level.
At 6000 ft elevation about 80% of that, 11.8 psi.

Mason jars can probably sustain that pressure from the outside (vacuum inside). I'm not sure if it holds when the same pressure is applied from the inside.
Click to expand...


https://www.ebay.com/itm/2745531157...%3D|ampid:PL_CLK|clp:2047675&epid=26036223532
the guage says 25psi when i pump it up on a glass jar. am i reading it wrong?


and honestly man, at this point....it would be worth the money to see my milk can emplode, when my cider is done fermenting...i am so filling it with 10 gallons of hot tap water and putting it in the fridge sealed! my milk can was relatizly cheap, so i would mind using it dented...or buying a new one, but this is something i just HAVE to see for myself!


(many appologies, but the only way i ever learn is the 'hard way'....;))
 
bracconiere said:
https://www.ebay.com/itm/2745531157...%3D|ampid:PL_CLK|clp:2047675&epid=26036223532
the guage says 25psi when i pump it up on a glass jar. am i reading it wrong?


and honestly man, at this point....it would be worth the money to see my milk can emplode, when my cider is done fermenting...i am so filling it with 10 gallons of hot tap water and putting it in the fridge sealed! my milk can was relatizly cheap, so i would mind using it dented...or buying a new one, but this is something i just HAVE to see for myself!


(many appologies, but the only way i ever learn is the 'hard way'....;))
Click to expand...
Only fill it half way so it will collapse better
 
Homebrew Harry said:
Only fill it half way so it will collapse better
Click to expand...


how about 2/3s? it's 16 gallons i plan on filling it with 10....i also want to pull the gauge off my vacuum pump to what kind of suction i get..... win or lose this will be fun! the boss is off in vegas planing card games, what's the difference!
 
bracconiere said:
how about 2/3s? it's 16 gallons i plan on filling it with 10....i also want to pull the gauge off my vacuum pump to what kind of suction i get..... win or lose this will be fun! the boss is off in vegas planing card games, what's the difference!
Click to expand...
It's your party...when I was in grade school, we put just a little bit of water in a 1 gallon metal gas can and heated it on a warming tray. It was winter and we opened the window and it did not take long for that can to draw up like you wouldn't believe.

Edit: we put the can in the cold open window.

Also I just got back from Vegas. Hope the boss doesn't do too bad !
 
Homebrew Harry said:
Also I just got back from Vegas. Hope the boss doesn't do too bad !
Click to expand...


me too!

Well anyway, i just laid my still fermenting cheap az milk can on it's side without pressure, and stood on it, i weigh 180lbs....and rolled it around and stuff under my feet, didn't bend a bit....so i'm still thinking it AIN'T going to implode if i stuck it in the fridge.... 🤔
 
You all just made me nervous about my process. I use a FermZilla All Rounder. When I cold crash, the sides collapse in but, in my mind, as long as the collar does not flex, I'm good to go.
When I transfer to the keg, I gently pressurize the All Rounder. The sides flex back, with a little bit of the trub going back into suspension when the sides "pop" back to their original position.
Now I'm wondering if the All Rounder has a finite number of times it can flex before it splits and explodes in my fermentation chamber.
If I understand correctly, once I take off the blowoff tube, I should pressurize the All Rounder to 5 PSI before cold crashing.
 
I ferment in a freezer. I usually will start cold crash at about 10 PSI in the headspace and check on it a few times a day as temp drops. Top up the head space as it starts to fall. For some beers I cold crash below 30F with freezer temp set to not get colder than 20F. I'll need to top up CO2 in headspace multiple times on one of those crashes.
 
I'm about a three or four days away from my FG. I like the 10PSI. I may pull the blowoff tube now and see how much CO2 I can naturally develop before pumping in anything.

Thanks for the advice.
 
Pablo 54 said:
You all just made me nervous about my process. I use a FermZilla All Rounder. When I cold crash, the sides collapse in but, in my mind, as long as the collar does not flex, I'm good to go.
When I transfer to the keg, I gently pressurize the All Rounder. The sides flex back, with a little bit of the trub going back into suspension when the sides "pop" back to their original position.
Now I'm wondering if the All Rounder has a finite number of times it can flex before it splits and explodes in my fermentation chamber.
If I understand correctly, once I take off the blowoff tube, I should pressurize the All Rounder to 5 PSI before cold crashing.
Click to expand...
5 psi may not be enough to counter the “shrinkage” when chilling the beer. I’m not sure what the pressure limits are for the all rounder but I would pressurize higher just to be safe or check occasionally throughout the crash to make sure you’re in positive territory and add pressure if needed.
 
Agreed. I think I'll go with the 10PSI suggested by eric19312. I disconnected the blow off tube. I'll check my pressure tomorrow and see where I'm at. I still have a few points to go.
 
bracconiere said:
i thought of that too, if people have to worry about putting a conical that costs $1k in the fridge, maybe a design improvement for them? :mug:
Click to expand...

No need. You just spend 10% more for a co2 tank and regulator since it has so many other uses anyway. There is little need to improve the vacuum potential.
 
bracconiere said:
.(and i just thought about canning, why don't all the mason jars implode?)
Click to expand...

The ability of a cylinder to withstand vacuum is related to the strength of the material and the radius. Mason jars have a pretty thick wall and small radius. On a larger tank, the material is pretty strong but the radius is is larger so it's more susceptible to buckling. In other words, the cross section is less of a dome, and more flat (relative to a mason jar).
 

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