# Fermenting In Cube - Forcing Expansion To Create Head Space



## squirt in the turns (15/10/12)

I'm an on/off no-chiller but have never fermented in the cube before. I've decided to give it a shot today. It's a 19L batch in a 20L cube (holds 23L or so in reality), so there should be enough head space for krausen. The trouble is that I squeezed the sides of the cube like a good no-chiller, and now that the cube has cooled, the sides are staying like that, meaning no head room.

I've just pitched the yeast (WY1272), and my idea is to screw the lid back on tight and let the pressure build up push the sides of the cube out, creating enough head space that I won't need a blow-off tube, then replace the lid with glad wrap. I'm just a bit concerned that HDPE is nowhere near as malleable when cold, so something else might give first. I.e. the tap will pop out, or a seam will rupture. Or it'll go nuts overnight and explode before I get up to check it.

Has anyone else tried this? I guess I'm deliberately trying to create the pressure conditions that occur in an infected no-chill cube. Anyone who's had one of those care to comment?


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## mje1980 (15/10/12)

Make sure its on tiles or lino so the clean up will be easy


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## mark0 (15/10/12)

mine usually pop out with a load of napisan inside. no issues so far with leaks.


should be fine, but release the gas as soon as the cube expands.


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## petesbrew (15/10/12)

Get a spare lid, drill a hole in it, shove in blowoff tube.
Simple really.


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## manticle (15/10/12)

Should be fine, provided you release it in a timely way. I have found various cubes will eventually split but never had a fermenting one give way.
However I fill my nc cubes as full as I can, squeeze air out as much as I can and find leaking krausen is generally minimal. Sucked in sides sort themselves out without needing to tighten the lid.
I keep them in a space where leakage does no damage and make sure I clean and sanitise around any leakag.


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## Ross (15/10/12)

petesbrew said:


> Get a spare lid, drill a hole in it, shove in blowoff tube.
> Simple really.




Perfect advice....


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## QldKev (15/10/12)

I think the OP issue wasn't about creating a blow off tube. 

"The trouble is that I squeezed the sides of the cube like a good no-chiller, and now that the cube has cooled, the sides are staying like that, meaning no head room."

So he was hoping to create positive pressure in the fermenting vessel to push the sides back out to achieve the maximum possible volume. 

While I think it would work, I think it would be asking for trouble the day you crack open the cap; or if you let the pressure build up too much things like taps may be pushed from their threads. I think for a few dollars I would get a separate jerry can, the dump from the storage into the fermenting one will help aerate it anyway. 


QldKev


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## squirt in the turns (15/10/12)

Thanks all for your advice. 

Petesbrew, I actually already had a suitably drilled lid, but it was covered in crap from lying around in the shed, it was late at night and I couldn't be bothered to clean it. There was literally ZERO head room in this cube: when I opened it to pitch the yeast, it didn't suck any air it, it just stayed the same shape. I aerated it using MHB's aeration kit. I was thinking I'd lose a lot of yeast/beer if I went with the blowoff tube, and I didn't want the mess/hassle (my fermentation chamber is a pain to clean), just the convenience I've heard of that comes with fermenting in the cube. I was actually worried I'd lose so much yeast this way that there wouldn't be enough left to finish the job (or is this a bit of a myth?).

It was a bit optimistic of me to be posting at 12:30 AM hoping for a response before morning when I'd have the answer one way or another anyway.  

It looked at first like it had worked perfectly: the cube was swollen and holding pressure. I'd left it on its side, tap up, so that if it did pop out I wouldn't immediately lose the whole batch. Released the pressure through the tap and nothing but gas came out - great, I thought. Gently righted the cube and went to remove the lid... apparently the pressure release and small amount of movement had got the yeast really excited as I suddenly had massive amounts of krausen escaping. After loosing at least a litre, I closed the lid (cube began swelling further), quickly sanitised a fermenter, and dumped the batch into it.

manticle, how do the cubes expand if you don't have internal pressure build up?


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## thylacine (15/10/12)

squirt in the turns said:


> I'm an on/off no-chiller but have never fermented in the cube before. I've decided to give it a shot today. It's a 19L batch in a 20L cube (holds 23L or so in reality), so there should be enough head space for krausen. The trouble is that I squeezed the sides of the cube like a good no-chiller, and now that the cube has cooled, the sides are staying like that, meaning no head room.
> 
> I've just pitched the yeast (WY1272), and my idea is to screw the lid back on tight and let the pressure build up push the sides of the cube out, creating enough head space that I won't need a blow-off tube, then replace the lid with glad wrap. I'm just a bit concerned that HDPE is nowhere near as malleable when cold, so something else might give first. I.e. the tap will pop out, or a seam will rupture. Or it'll go nuts overnight and explode before I get up to check it.
> 
> Has anyone else tried this? I guess I'm deliberately trying to create the pressure conditions that occur in an infected no-chill cube. Anyone who's had one of those care to comment?




Perhaps an opportunity for you to try "top-cropping" yeast. eg. 

Cheers...


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## Ross (15/10/12)

squirt in the turns said:


> I was thinking I'd lose a lot of yeast/beer if I went with the blowoff tube, and I didn't want the mess/hassle (my fermentation chamber is a pain to clean), just the convenience I've heard of that comes with fermenting in the cube. I was actually worried I'd lose so much yeast this way that there wouldn't be enough left to finish the job (or is this a bit of a myth?).



Blow off tube will not remove yeast & stall your ferment. Also, the whole basis of the blow off tube is to avoid mess/hassle. Try using glad wrap & there's every chance it'll spew everywhere.

cheers Ross


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## [email protected] (15/10/12)

Air locks, tubes, glad wrap all a whole lot of stuffing around that is not needed.

Plain lids backed of a notch from sealing are so much easier, no mess no fuss....just saying...


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## manticle (15/10/12)

My guess is that the slow release of gas through the not quite tight lid means there is still pressure inside. cube sides are squeezed in after nc and relax to normal form during fermentation.

Fermenting in the cube is meant to be a hassle free process - if you overthink it, you negate the simplicity and might as well use an extra vessel.


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## S.E (15/10/12)

A cube will take a lot of pressure, I use cubes as casks and have never had one burst. If you just want to push out the sides a bit dont screw the cap on too tight so it leaks as the pressure builds up.


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## [email protected] (18/10/12)

Next time, just pour a large cup of hot water into the cube, put the lid on and shake like crazy. The hot water will heat the air, causing it to expand and pop out the sides.

I think.


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## squirt in the turns (18/10/12)

endisnigh said:


> Next time, just pour a large cup of hot water into the cube, put the lid on and shake like crazy. The hot water will heat the air, causing it to expand and pop out the sides.
> 
> I think.



Yep, works perfectly. Just not when there's already 20 L of fermenting beer in the cube


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## MetalDan (30/6/16)

Sorry to bring up an old thread, but couldn't find the answer anywhere else and its related.

I've always used glad wrap to cover a cube when fermenting, but have decided to try out just turning back the cube lid instead (as Beer4U mentioned above). Any suggestions on how much to notch batch? I've just put down a porter and notched it back 1/2 a turn, is that about right?


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## manticle (30/6/16)

Should be loose but remain on. Cube will swell if it's too tight so you'll know if it's bulging when you check in a few hours and you can back it off more.

I tighten then back off a few turns - probably halfway between tight and off if that makes sense.


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## wynnum1 (30/6/16)

Have a used blue liquid chlorine drum and the top has an air vent using one of these tops as a replacement and leave original for when wanting to seal may be better then putting hole in original.


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## MetalDan (30/6/16)

Cheers mants. There was some minimal pressure in the cube so I just turned back until I heard the pressure escape (at the 1/2 turn mark), and then tightened slightly. I might turn it another turn or so, so its on but not restrictive.

Cheers


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