Fermenting Under Pressure

[Yuz]

Maybe slightly OT, but I've just done a 28L 1.040 batch and set to 15PSI, in 40 odd hours since pitching W34/70 (15g) it has dropped to 11PSI and is sitting at this ATM... Krausen has settled alot as well. An identical gravity-brewed batch would have Krausen hanging around for three days at least... It fermentation slowing down or have I killed the yeast?
I don't have temp control but Melb weather has been fairly stable and the brew is well insulated.

 

[wide eyed and legless]

I don't think the yeast like it, I did a stout last brew and applied to much pressure I believe, looked to be finished but 24 hours after dropping the pressure off fermentation started again and dropped 4 points more. It definitely suppresses the krausen though.

 

[Yuz]

Weal, yeah I had that suspicion - so I've gradually built up the pressure so the yeast can adjust... I'll also slowly reduce the pressure once this batch is kegged so I can re-use these yeasties.
Odd that the common perception is pressure brewing is meant speed up the process - but it seems to be the opposite as the yeast is suppressed?
Earlier post on this thread suggests that W34/70 (and other strains) had no issues at much higher 21PSI, and reading other resources I thought around 15PSI would be the happy medium? Well, we'll see how it turns out

 

[wide eyed and legless]

What are you brewing, and did you watch the podcast I put up on the bulk buy thread? WLP 925 for a lager yeast at one Bar.

 

[Yuz]

Weal, it's a lager-like brew, partial BIAB: Pale Ale Malt 1.5kg + 1kg Munich + Caraaroma 100g & Hallertau MF late in boil.
Plus Coopers Lager Can. I'm yet to go full AG so I've been doing half BIAB / half can for now...
I've been using dry Yeasts so I went with something familiar so I can suss out the whole pressure ferment process
I'll have another look at the podcast to understand it a bit better.

 

[droid]

Maybe slightly OT, but I've just done a 28L 1.040 batch and set to 15PSI, in 40 odd hours since pitching W34/70 (15g) it has dropped to 11PSI and is sitting at this ATM... Krausen has settled alot as well. An identical gravity-brewed batch would have Krausen hanging around for three days at least... It fermentation slowing down or have I killed the yeast?
I don't have temp control but Melb weather has been fairly stable and the brew is well insulated.

1.040OG ? it could be done, what's your expected FG?

15PSI is no problem, I brew all mine at 15PSI and once the pressure drops it's done. 1.040 is around the gravity you might use for a yeast starter and with the right amount of yeast 40hours, especially under pressure could be enough. If you had been fermenting at 9C this time-frame could be a problem but if at ambient 22 or something then yeah.

Can't comment on the resulting taste of 34/70 at that temp tho

 

[Yuz]

Hey Droid, the projected FG is 1.009, I'll check it later today (72hours after pitching);
I always hydrate the yeast, and this one was a quick starter as usual (20deg wort) - active visible ferment within four hours but geez this is QUICK if it has infact chewed through all the fermentables! The pressure's been sitting at 8PSI since yesterday.

 

[wide eyed and legless]

Hey Droid, the projected FG is 1.009, I'll check it later today (72hours after pitching);
I always hydrate the yeast, and this one was a quick starter as usual (20deg wort) - active visible ferment within four hours but geez this is QUICK if it has infact chewed through all the fermentables! The pressure's been sitting at 8PSI since yesterday.

So how is it going? I still have yet to do a lager in my system, will be soon, I have quite a bit of pilsner malt.

 

[Yuz]

Hey Weal, my super-accurate (and calibrated!) eBay refractometer read @ 1.016 on Saturday. So in real terms, considering the correction factor it could well be done fermenting by now.
The pressure has also dropped to 2PSI (I'm assuming absorbed by the brew?) and is staying on that since sampling - I wasn't sure if it was meant to be maintained constant through the fermentation?
I'll let it sit for for a couple more days, keg and force carb it. If it's a stuff up - lesson learnt. But smelling the sample it seemed ok.
I'm looking to re-use this yeast too.

 

[wide eyed and legless]

I presume you are doing this in your Fermentasaurus, are you dropping the pressure or is it dropping by itself?

 

[Digga]

Would have to say that if you have kept the brew at the same temp and your dropping psi then you have a leak somewhere. Only when you drop the temp should it absorb Co2. Correct me if I'm wrong here.

 

[Yuz]

Weal - yes, in the Fermentasaurus. The pressure has dropped gradually by itself - whether the co2 is leaking or got absorbed I'm not sure, but it's still maintaining some (minimal) pressure.
Digga - my understanding is that co2 is still absorbed (at a slower rate) at room temp? I'm yet to setup a fermenting fridge...

 

[wide eyed and legless]

I agree with Digga you must have a leak, the idea is let the pressure out while fermenting and then apply pressure to carbonate your brew towards the end.

 

[Yuz]

I think the leak culprit is Fermentasaurus' top gasket - took me four goes to seal it up (using KegLube as well) but obviously still leaks through a little.

 

[wide eyed and legless]

Wonder if that's the reason it is being revamped? Is the gasket quite hard or a little soft?

 

[Yuz]

Wonder if that's the reason it is being revamped? Is the gasket quite hard or a little soft?

The Gasket doesn't hold shape once in place - the flanges deform once the top Cap is pressing down on it. Plus as the Collar is screwed on, it grabs and pulls on Gasket edges. I can only get it in place properly if I force down the top cap while fixing the Collar. Defo needs a Revision B IMHO, unless they have already?

 

[markp]

The Gasket doesn't hold shape once in place - the flanges deform once the top Cap is pressing down on it. Plus as the Collar is screwed on, it grabs and pulls on Gasket edges. I can only get it in place properly if I force down the top cap while fixing the Collar. Defo needs a Revision B IMHO, unless they have already?

There is a right way up for the seal and a wrong way, there is a lip on the inside edge of the seal which sits inside the neck of the fermenter and this stops the seal pushing out and deforming.
Not saying that you are not putting it the right way up but just a thought as mine seals first time every time without any mucking around, I place the seal on the cap, place the cap on the fermenter and then screw the collar on tight and all’s good.
Cheers.

 

[Yuz]

There is a right way up for the seal and a wrong way, there is a lip on the inside edge of the seal which sits inside the neck of the fermenter and this stops the seal pushing out and deforming.
Not saying that you are not putting it the right way up but just a thought as mine seals first time every time without any mucking around, I place the seal on the cap, place the cap on the fermenter and then screw the collar on tight and all’s good.
Cheers.

There may be a batch / manufacturing tolerance issues with the one I've got. It certainly isn't an operator's error lol

 

[wide eyed and legless]

It has been an occurring problem in the threads regarding Fermentasauri

 

[wide eyed and legless]

As a few will have already read the posts and technique of pressure fermenting in a cube, going to be brewing a hoppy AIPA , not often I do them, but needed a way to introduce the hops under pressure without venting the cube.
So have made a hop dropping chamber to dry hop and no pressure lost, simple and cheap to make will also adapt to other systems.

Under pressure.


Hop dropper fitted, insert hops into nipple, 150 mm should be enough this one is overkill at 300 mm, fit top cap, I have fitted a barb on mine to divert gas from ferment to the dropper not really necessary, open ball valve releasing the hops into fermenter. Close ball valve job done.