[JT]

Thanks for the update.  My fermenters won't be here in time for a Best Bitter I'm brewing tomorrow, so back to the old glass carboy for me.
Interested in how long it takes you to reach FG and whether that differs from your expected FG.  Also, any tasting notes. 

[Robert]

UPDATE
66 hours, 45.3% AA, pH 4.31.  Will sample again later today, still awaiting >50% AA, at which point SOP is to allow free temperature rise to 70°F controlled ambient.   Very slow, this batch.  But no signs of other abnormalities.  I can be patient as long as the result is good.

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[ynotbrusum]

Interesting stuff, for sure.  I now have the 13.6 gallon kegmenter for my 10 gallon batches and an interesting pressure valve that Williams sells from Australia called the “BlowTie” which hooks up with simple push fit collets (like my RO system - tubing 8mm, IIRC).  I am sending this remotely, so I don’t have the links handy, but with a valve and some short tubing a couple fittings and a gauge, I prepped a system to try out pressure fermenting.  Lastly, BYO has a recent replication recipe for an Altbier that a brewery in Vermont ferments under pressure, with English ale yeast no less!  So, I might have to give that a try!  Gotta cut off the dip tube on the kegmenter about a half inch, which is my most fearful step....

[narcout]

The benefit of fermenting under pressure that I always hear about (and maybe read about in Yeast?) is that it suppresses esters, allowing you to ferment at a warmer temperature and finish more quickly than you would otherwise. 

Is that what you're after or are there other benefits?

[Robert]

The benefit of fermenting under pressure that I always hear about (and maybe read about in Yeast?) is that it suppresses esters, allowing you to ferment at a warmer temperature and finish more quickly than you would otherwise. 

Is that what you're after or are there other benefits?

My interest is in having a simple, completely closed system,  and the added benefit of a ready supply of CO2 for drawing samples.   I don't really want to change the fermentation character,  though that will be something to explore in the future.   And yes, Chris and Jamil's book says increased head pressure decreases esters and fusels.   But some xBmts may suggest this effect is negligible.

(I wanted to follow my SOP regarding temperature program, and everything else, this batch because, well one variable at a time, right?  Science.  Next batch I may run at a steady, higher temperature.   I'm also interested in the viability and/or adaptation of repitched yeast from pressure  fermentation.   Much to learn.)

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[Robert]

UPDATE
72 hours.   50.2% AA, pH 4.23, allowing free rise to 70°F ambient.

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[JT]

The benefit of fermenting under pressure that I always hear about (and maybe read about in Yeast?) is that it suppresses esters, allowing you to ferment at a warmer temperature and finish more quickly than you would otherwise. 

Is that what you're after or are there other benefits?

My interest is in having a simple, completely closed system,  and the added benefit of a ready supply of CO2 for drawing samples.   I don't really want to change the fermentation character,  though that will be something to explore in the future.   And yes, Chris and Jamil's book says increased head pressure decreases esters and fusels.   But some xBmts may suggest this effect is negligible.

(I wanted to follow my SOP regarding temperature program, and everything else, this batch because, well one variable at a time, right?  Science.  Next batch I may run at a steady, higher temperature.   I'm also interested in the viability and/or adaptation of repitched yeast from pressure  fermentation.   Much to learn.)

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+1 on sampling, but also just ease of transfer.
 
With a brew bucket, I have option of using a ball valve, but then having to close the valve and just be satisfied with cleaning the exterior of the valve as best I can.  Not to mention having to lift the fermenter to accomplish any of this. 
With the glass carboy I have the option of inserting a thief into the beer to draw a sample.  Have to open the fermenter to accomplish this. 
With a plastic bucket I have the option to open a very large area to use the thief or use a spigot... same issues as the brew bucket with that. 

Transfering to a keg should be just as easy as sampling.  In the event a spunding window is missed, I have to belief this option would introduce less o2 than my current transfer operation from a glass carboy. 

[Robert]

I've been greatly enjoying the ease of sampling and transfer, as well as peace  of mind, since switching to ball lock fitted fermenters even when fermenting at atmospheric pressure.   Before the 10 gallon corny, for a time I used a Speidel that I had customized with ball lock in and out posts, and used the same improvised airlock as I had on the corny until now.  BTW this is another way I know that 7.5 gallons is plenty to ferment 6 gallons without fouling the gas post at the top of the vessel,  which should reassure you, JT.  My horror at the prospect of maintaining sanitary conditions with a ball valve is why I have been determined for some time to find a corny-like solution rather than a typical conical.  Turns out a corny is pretty corny-like.

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[denny]

And yes, Chris and Jamil's book says increased head pressure decreases esters and fusels.

That's why I want to get Chris's chart.  Wide variety of results depending on yeast strain, temp and pressure.

[ynotbrusum]

I look forward to the chart, Denny, because with the new genome information that keeps coming out, it will compliment the knowledge base nicely to know the pressure effects of these various sugar fungi that we had so many preconceptions and misconceptions about in our prior classification system....

[Robert]

4 days.  64.0% AA, pH 4.24.  Has risen only to 66°F, activity seems to have wound down but yeast not heavily flocculating yet.  Was expecting 69-70% AA, will continue to monitor.

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[Robert]

UPDATE
6 days.   No further attenuation,  yeast dropped.  So, somewhat underattenuated, but ultimately finished in the same time as a batch at atmospheric pressure would be expected to.  (It is not out of the realm  of possibility that some, but I think not all, of the underattenuation could be accounted for by a slightly higher mash pH -- an international adjustment -- than the previous batch of a nearly identical beer used as a reference.)  I have a feeling that if I plotted enough data, the attenuation on this pressurized batch would look more like a straight slope than the right half of a bell we're used to.  Whatever that means.  So I'll crash this and rack it in a few days.  SOP is a couple weeks at least "lagering" at 30°F before a couple weeks in the keezer carbonating.   When I taste it I'll report.   Meanwhile I'll brew again next weekend.   I plan to pressure ferment that batch, but at a higher temperature throughout.   I'll report progress on that here as well.

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[narcout]

Cool; I'll look forward to hearing how the next batch goes.

I haven't used S-04 for a while, but 64% AA seems pretty low, right?

I've got a Tripel finishing up fermentation now in a 10 gallon corny keg with spunding valve attached. It seems to be generating about 4 psi every 12 hours (when it gets to 5, I manually bleed it back to 1). 

[Robert]

Cool; I'll look forward to hearing how the next batch goes.

I haven't used S-04 for a while, but 64% AA seems pretty low, right?

I've got a Tripel finishing up fermentation now in a 10 gallon corny keg with spunding valve attached. It seems to be generating about 4 psi every 12 hours (when it gets to 5, I manually bleed it back to 1).

64% isn't out of the normal range for S-04  IME, depending on the recipe.  It sometimes is described as attenuative,  but it's still English, doesn't eat maltotriose, etc.  It is lower attenuation than I expected for this beer based on 69.7% (IIRC) for a previous, nearly identical, recipe.  But this is just one batch, one data point,  could be a fluke, or not. But I'll say one thing -- I detect no flavors that need cleaning up whatsoever.   It hit final gravity ready to crash cool.  So the method may save time, and I'm confident about fermenting the next one warmer to see if that speeds it up in the early stages and gets it to attenuate further.  Pressure fermentation so far has fulfilled all my other expectations as far as convenience, easy sampling, peace of mind about oxygen exclusion,  etc.  I plan to make this my standard practice,  I just have to learn what adjustments I'll have to make in recipes and timetables.  And get the hang of the PRV a little better.

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[Robert]

I submitted the following query on both Lallemand's and Fermentis' websites.  (The wet guys' websites don't seem to offer a way to submit technical questions,  and I'm keen on dry yeast lately anyway.)  I'll post any replies I receive.

"I am a homebrewer switching to a new system, fermenting under 5-6 psig head pressure. What considerations should I be aware of regarding yeast performance? Should I alter fermentation temperature or pitching rate? Are there differences in suitability to these conditions among strains? Thank you in advance."

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