Quantcast

Cold crash suck-back volume estimate?

HomeBrewTalk.com - Beer, Wine, Mead, & Cider Brewing Discussion Community.

Help Support Homebrew Talk:

SmokeyRydr

BeachMonkey.Beer
HBT Supporter
Joined
Mar 15, 2018
Messages
132
Reaction score
102
Location
Seattle, WA
is there any general guidance for the volume of gas being sucked back when cold crashing?

E.g. if I have a 6.5g carboy and 5.5g of beer, and I cold crash from 68F to 35F, what volume of gas should I expect to suck-back?

if this is pretty constant and predictable, I'd like to create a large enough "gas reservoir" in my blow-off system to prevent both sanitizer and O2 from pulling back into my carboy.

FWIW, I'm thinking of just creating enough of a "gas reservoir" by lengthening my blow-off tube to provide enough volume.
 

RPh_Guy

Bringing Sour Back
HBT Supporter
Joined
Jan 26, 2017
Messages
9,213
Reaction score
7,561
Location
Cleveland
The volume of gas will decrease proportionally to the temperature in degrees Kelvin.

68F is 293
35F is 275
With your numbers, the volume of gas will contract by about 6.1%, so you need about 0.065 gallons of reserve CO2 to prevent suckback. :)

If you are truly concerned about oxygen, spunding is the way to go, definitely no cold crash.

Cheers
 

day_trippr

"Now brewing exclusively with Hydrohydroxic Acid"
Joined
May 31, 2011
Messages
35,117
Reaction score
17,009
Location
Stow, MA
We routinely see reports of a quart of sanitizer sucked into carboys. I'd make sure to cover at least that much...

Cheers!
 
OP
SmokeyRydr

SmokeyRydr

BeachMonkey.Beer
HBT Supporter
Joined
Mar 15, 2018
Messages
132
Reaction score
102
Location
Seattle, WA
So, I guess if I want to extend my blowoff hose to be a CO2 reservoir, I'm going to need a REALLY LONG hose... [emoji1787][emoji1787][emoji1787]
 

day_trippr

"Now brewing exclusively with Hydrohydroxic Acid"
Joined
May 31, 2011
Messages
35,117
Reaction score
17,009
Location
Stow, MA
Or a pretty good size mylar balloon on the far side of a catch vessel. With a bit of plumbing that should allow any liquids to end up in the catch vessel while the gases end up in the balloon...

Cheers!
 

Bobby_M

Vendor and Brewer
HBT Sponsor
Joined
Aug 3, 2006
Messages
25,069
Reaction score
3,942
Location
Whitehouse Station
I have observed a wild variation in the volume to satisfy the vacuum. A 6 gallon batch in a 7 gallon fermonster completely deplete a 1 gallon bladder on me twice. Other times it only deflates half way. I decided to just upgrade to 2.5 gallon bladders on my cold crash guardian product.
 

HarlemBrewDoug

Supporting Member
HBT Supporter
Joined
May 5, 2016
Messages
150
Reaction score
82
Location
Harlem, New York
I have observed a wild variation in the volume to satisfy the vacuum. A 6 gallon batch in a 7 gallon fermonster completely deplete a 1 gallon bladder on me twice. Other times it only deflates half way. I decided to just upgrade to 2.5 gallon bladders on my cold crash guardian product.
With V3 of the Guardian being tested, do you have an idea when it'll be back and available? If you're looking for another tester, I'm sure I could find one...
 
OP
SmokeyRydr

SmokeyRydr

BeachMonkey.Beer
HBT Supporter
Joined
Mar 15, 2018
Messages
132
Reaction score
102
Location
Seattle, WA
I ended up with this...

I'm connected to the beer side so CO2 should fill from bottom up. And when cold crashing, suck CO2 from bottom. Bubbler, airlock will let in O2, not liquid.

Not shown is the intermediate collection jar that I started with, but since I have a 7 gal fermenter for 5.5gal. I prob don't need it.

20200204_131008.jpeg
 

doug293cz

BIABer, Beer Math Nerd, ePanel Designer, Pilot
Staff member
Mod
Lifetime Supporter
Joined
May 14, 2014
Messages
11,013
Reaction score
7,142
Location
Renton
I've used a 3 piece airlock and have had zero suck back.
You're still going to get oxygen drawn in with that setup :(
We're taking about air suckback, not liquid.
There are many people who claim that three piece airlocks allow liquid suck-back. As @Tobor_8thMan notes, a properly filled three piece airlock will not suck back liquid.

No liquid filled airlock can prevent air suck back during cold crashing.

Brew on :mug:
 

doug293cz

BIABer, Beer Math Nerd, ePanel Designer, Pilot
Staff member
Mod
Lifetime Supporter
Joined
May 14, 2014
Messages
11,013
Reaction score
7,142
Location
Renton
I ended up with this...

I'm connected to the beer side so CO2 should fill from bottom up. And when cold crashing, suck CO2 from bottom. Bubbler, airlock will let in O2, not liquid.

Not shown is the intermediate collection jar that I started with, but since I have a 7 gal fermenter for 5.5gal. I prob don't need it.

View attachment 665654
Filling from the bottom up, and drawing from the bottom make no difference. The flow rate of CO2 during fermentation is not high enough to create any gas sweeping effect in a keg used as a CO2 reservoir. Gases (air and CO2) mix in a mater of minutes - there is no CO2 "blanket" or layer on the bottom of a vessel.

Brew on :mug:
 

day_trippr

"Now brewing exclusively with Hydrohydroxic Acid"
Joined
May 31, 2011
Messages
35,117
Reaction score
17,009
Location
Stow, MA
Well....

If 100% repeatable empirical test results mean anything, then the statement "a properly filled three piece airlock will not suck back liquid" is not precise.

I'm not going to put up a youtube video because the act looks stupid :D but I invite anyone to duplicate my test in the privacy of their own whatever: attach a length of tubing to the stem of a standard 3 piece lock, drop the float inside, fill to the middle of the two prescribed fill lines with potable fluid, put the cap on, then just try sucking on the tube without draining half the filled volume...every time.

It does appear it reaches some static state wrt fluid level, so it's not going to go totally dry in any short order, though I could keep pulling more fluid out with a bit of effort (presumably a few orders of magnitude more than the lock would experience atop a carboy or bucket)...

Cheers!
 

doug293cz

BIABer, Beer Math Nerd, ePanel Designer, Pilot
Staff member
Mod
Lifetime Supporter
Joined
May 14, 2014
Messages
11,013
Reaction score
7,142
Location
Renton
Well....

If 100% repeatable empirical test results mean anything, then the statement "a properly filled three piece airlock will not suck back liquid" is not precise.

I'm not going to put up a youtube video because the act looks stupid :D but I invite anyone to duplicate my test in the privacy of their own whatever: attach a length of tubing to the stem of a standard 3 piece lock, drop the float inside, fill to the middle of the two prescribed fill lines with potable fluid, put the cap on, then just try sucking on the tube without draining half the filled volume...every time.

It does appear it reaches some static state wrt fluid level, so it's not going to go totally dry in any short order, though I could keep pulling more fluid out with a bit of effort (presumably a few orders of magnitude more than the lock would experience atop a carboy or bucket)...

Cheers!
This doesn't match with my experiments.

Brew on :mug:
 

day_trippr

"Now brewing exclusively with Hydrohydroxic Acid"
Joined
May 31, 2011
Messages
35,117
Reaction score
17,009
Location
Stow, MA
Really? I mean, literally, every freakin' trial result was the same here. Half the prescribed volume ran right down the tubing into my mouth (well water, thanks).

Is there something magical about your particular lock - or maybe something fatally effed up with mine (that I haven't used them in forever?)

Cheers!
 

doug293cz

BIABer, Beer Math Nerd, ePanel Designer, Pilot
Staff member
Mod
Lifetime Supporter
Joined
May 14, 2014
Messages
11,013
Reaction score
7,142
Location
Renton
Really? I mean, literally, every freakin' trial result was the same here. Half the prescribed volume ran right down the tubing into my mouth (well water, thanks).

Is there something magical about your particular lock - or maybe something fatally effed up with mine (that I haven't used them in forever?)

Cheers!
I'll go back and recheck.

Brew on :mug:
 

day_trippr

"Now brewing exclusively with Hydrohydroxic Acid"
Joined
May 31, 2011
Messages
35,117
Reaction score
17,009
Location
Stow, MA
lol! Yeah, do that, and we can feel silly together :D
I actually just thought of a way to do it without it looking completely moronic, just need a suitable suction bulb or a friggin' big syringe...

Cheers!
 

doug293cz

BIABer, Beer Math Nerd, ePanel Designer, Pilot
Staff member
Mod
Lifetime Supporter
Joined
May 14, 2014
Messages
11,013
Reaction score
7,142
Location
Renton
lol! Yeah, do that, and we can feel silly together :D
I actually just thought of a way to do it without it looking completely moronic, just need a suitable suction bulb or a friggin' big syringe...

Cheers!
Also need to not pull air thru orders of magnitude faster than an cold crash can.

Brew on :mug:
 

day_trippr

"Now brewing exclusively with Hydrohydroxic Acid"
Joined
May 31, 2011
Messages
35,117
Reaction score
17,009
Location
Stow, MA
That was only after I had reached that halfway point - and I'm pretty sure that isn't dependent on excessive vacuum...

Cheers!
 

monkeymath

Well-Known Member
Joined
Jan 18, 2019
Messages
221
Reaction score
185
The bigger factor than pressure drop due to temperature is CO2 reabsorption from the headspace. You can find an analysis I did here.

Brew on :mug:
I apologize in advance for being scientifically illiterate (and for being literally illiterate in case that expression does not make any sense), but how exactly does (re) absorption of CO2 work? In your model, you seem to assume that the volume of the liquid (beer in this case) does not change when it absorbs CO2, so that the pressure actually drops and ambient air is sucked in.


Now, this "subadditivity" of volume is not an uncommon phenomenon - mix 50ml of sugar into 100ml of water, the resulting solution will have a volume very close to 100ml - and it sure seems crazy to think you could "inflate" your beer with gas.
But the sugar crystals in our kitchen are macroscopic objects, not individual molecules, and it seems plausible to me that the sugar molecules simply arrange differently - not in a crystalline grid - when dissolved in water, which causes the volume of the solution to be much closer to the volume of the water you started with, to some extent irrespective of the volume of sugar.

This might be very different for a gas like CO2. Given that CO2 is so willing to escape once the pressure drops, I'm wondering just how completely "dissolved" the CO2 really is.
 

Soulshine2

Well-Known Member
Joined
Jan 28, 2017
Messages
2,127
Reaction score
984
Location
Grant
is there any general guidance for the volume of gas being sucked back when cold crashing?

E.g. if I have a 6.5g carboy and 5.5g of beer, and I cold crash from 68F to 35F, what volume of gas should I expect to suck-back?

if this is pretty constant and predictable, I'd like to create a large enough "gas reservoir" in my blow-off system to prevent both sanitizer and O2 from pulling back into my carboy.

FWIW, I'm thinking of just creating enough of a "gas reservoir" by lengthening my blow-off tube to provide enough volume.
remove the airlock , put a star san soaked cotton ball or rag over the hole. cold crash.
 

monkeymath

Well-Known Member
Joined
Jan 18, 2019
Messages
221
Reaction score
185
Can't give you an exact number, but I use these mylar balloons:

https://www.amazon.com/AKIO-CRAFT-B...?keywords=mylar+balloon&qid=1580934891&sr=8-1

If I fill one up completely, crashing from 70 to 38 degrees will take about half the CO2 out of the balloon. I think you would need an impractical amount of tubing to prevent suckback. The balloons are really cheap and easy.
That seems to be reasonably straightforward. Before attaching them, do you soak them in starsan or something?
 

anteater8

Well-Known Member
Joined
Apr 22, 2015
Messages
301
Reaction score
264
Location
Portland
That seems to be reasonably straightforward. Before attaching them, do you soak them in starsan or something?
I don't. They come completely flat, almost like they're vacuum sealed, so you have to cut a little notch off the end to stick your tube inside. I would rather not introduce any oxygen to the inside of the balloon when trying to sanitize it, so I just use it as is. No negative impacts to my beer.
 

anteater8

Well-Known Member
Joined
Apr 22, 2015
Messages
301
Reaction score
264
Location
Portland
remove the airlock , put a star san soaked cotton ball or rag over the hole. cold crash.
This would only prevent airlock liquid from getting sucked back, but what you really want to avoid is air getting sucked back. Air can definitely travel through a cotton ball or rag so I wouldn't recommend this method.
 

RPh_Guy

Bringing Sour Back
HBT Supporter
Joined
Jan 26, 2017
Messages
9,213
Reaction score
7,561
Location
Cleveland
do you soak them in starsan or something?
I have heard that Star San will degrade the material.
This might be very different for a gas like CO2.
Without getting into specifics, yes. The dissolved gas is basically in liquid state, and takes up a lot less space than gaseous state.
The volume increase from the dissolved CO2 is relatively negligible, and partly offset by the thermal contraction on the fluid.
I haven't checked his calculations but a model based on just the thermal contraction and dissolution of the gas does provide a good rough estimate for the amount of suckback.
 

Soulshine2

Well-Known Member
Joined
Jan 28, 2017
Messages
2,127
Reaction score
984
Location
Grant
This would only prevent airlock liquid from getting sucked back, but what you really want to avoid is air getting sucked back. Air can definitely travel through a cotton ball or rag so I wouldn't recommend this method.
whatever, youre not aerating with it, just reverse venting. big difference.
 

Soulshine2

Well-Known Member
Joined
Jan 28, 2017
Messages
2,127
Reaction score
984
Location
Grant
if you're ok with oxygen exposure that's fine, but the purpose of this thread is to discuss methods of avoiding it since it will negatively impact your beer (particularly hoppy styles).
im not ok with excessive oxygen exposure. and im more than ok with my beer results. I think everyone overthinks a lot on certain points and not looking at the big end result picture. I dont go out of my way , I just prevent it in the areas I can control. do what you want. I just stated what I do . and it works.
 

Soulshine2

Well-Known Member
Joined
Jan 28, 2017
Messages
2,127
Reaction score
984
Location
Grant
Yes, it's a completely different type of oxygen, the kind that won't ruin your beer... :confused:
normal breathing air in a normal environment consists of an avg of 20% oxygen. apparently I dont know what beer ruined by exposure to oxygen tastes like so why dont you enlighten me on signs of that instead of going straight to being a smart @$$ just because I dont belong to your LODO thought process.
Ive been homebrewing for over 4 years and at least a dozen AG brews.
For decades ,brewers have fermented in open vats and I dont think any of those were "ruined" by being exposed to oxygen. In fact, those open fermented beers are probably the best tasting old world styles.
 

Robert65

Major Obvious (recently promoted)
HBT Supporter
Joined
Jul 15, 2019
Messages
1,891
Reaction score
2,372
Location
Akron, Ohio
Open fermentation is a different story. During active fermentation, yeast will consume the oxygen before it has a chance to participate in oxidative reactions that damage beer, and it may indeed make for better beer through happier yeast (that depends on the yeast, and other variables.) After active fermentation has abated, the beer has no such protection, and any oxygen will only lead to staling. Those traditional, open fermented beers were transferred to closed lagering vessels or casks before active fermentation was finished, so any oxygen remaining was still scavnged as the beer finished fermenting and naturally carbonated. The old timers may not have fully understood what they were doing, but serendipitously hit on a good system.
 

anteater8

Well-Known Member
Joined
Apr 22, 2015
Messages
301
Reaction score
264
Location
Portland
normal breathing air in a normal environment consists of an avg of 20% oxygen. apparently I dont know what beer ruined by exposure to oxygen tastes like so why dont you enlighten me on signs of that instead of going straight to being a smart @$$ just because I dont belong to your LODO thought process.
Ive been homebrewing for over 4 years and at least a dozen AG brews.
For decades ,brewers have fermented in open vats and I dont think any of those were "ruined" by being exposed to oxygen. In fact, those open fermented beers are probably the best tasting old world styles.
Since you asked, BJCP lists characteristics of oxidized beer as "stale, papery, cardboard" and lists these possible solutions: "Check for oxygen being introduced into beer post-fermentation. Don't splash when racking/bottling. Check caps and/or keg seals for good fit. Purge bottles/kegs with CO2 prior to filling. Store beer cool. Drink beer when fresh."
 
Top