Mad Scientist Brewhaus, on Flickr
The blue handle keg is my dedicated 'spartanburg' keg that my spunding valve rides one.
11/21/11 by Mad Scientist Brewhaus, on Flickr
This is the counter pressure transfer in action. This was a 14 day grain-to-glass brew!
10/5/11 by Mad Scientist Brewhaus, on Flickr
As found on the Home Brew Talk forum, from which I learned all about this technique
General Techniques/Closed-system pressurized fermentation technique! (by WortMonger)
(The following is WortMonger's summary)
You should do the entire fermentation at fermentation temperature at whatever pressure you are wanting to (5-15 fermenting and then upwards of 30psi (30 psi = 207 KPa) for carbonation). Then a few gravity points from completion you simply let the keg build up as much pressure as it wants (Sankes will hold 60 psi (60 psi = 414 KPa) Cornys will hold 130 psi (130 psi = 896 KPa) so you don't have to worry about blowing one up because you shouldn't get much over 30 psi (30 psi = 207 KPa)) and this is where you are getting your carbonation from. After fermentation is completed, (I wait 1 week total from pitch) then turn down the temperature or move your brew to a lower temperature place where you can crash cool to clarify your beer and lower the pressure. Pressure decreases with temperature so this is where you dial in the carbonation level wanted and let it rest cold (like 33- 35*F) and crash the yeast to the bottom of the fermenter for 1 week. Then transfer under counter pressure to your serving keg and VIOLA!!!! The diacetyl is taken back in by the yeast the couple of days after fermentation has ceased but is still at fermentation temperature. Fermentation is usually over in 3-4 days so you have 3-4 days after that to clean up the diacetyl. The pressure doesn't matter for diacetyl removal only the yeast, and the yeast are still working at 30 psi (30 psi = 207 KPa) just not as fast. They are also not working on producing alcohol as they are to removing the diacetyl and will continue to work once the beer goes through crash cooling. Diacetyl rests are usually done a little warmer than fermentation temperature, but then again this is not your normal way to brew, so it is different. I have not had a single problem with any batches ...
I [am] interested in faster beer (carbonation maturation period running consecutively with secondary maturation period without changing a vessel or exposure to oxygen), and figured if it worked great on my ales then lagers (which is the main reason I attempted this) would be even better with the system. It works, and the yeast love the pressure not hate it!
I do bump my temperature up about 4 degrees (4 °F = -15.6 °C) after the majority of yeast has done its job as a insurance policy against diacetyl, as well as speeding up the finish.
With a keg and the techniques in this thread... Chill and Fill (or no-chill technique if you choose to), Ferment (and collect from cropping if set up), Lower esters and fusels (or don't and ferment like normal open to your blow-off buckets water pressure or airlock if you build it that way), Carbonate to finishing volumes while doing a diacetyl rest and then crash cool to settle and clean (or transfer after fermenting, crashing, resting and force carbonate later in your serving vessel like you've always done before). There is no down-side to me if you already keg your beer and can afford to build the spunding valve (which comes in really handy as a multi-tasker in the brew house filling kegs under counter-pressure).
[Setting spunding valve at 5 - 7 psi (7 psi = 48.3 KPa)]
I differ in that I hold my beer at 5 - 7 psi (7 psi = 48.3 KPa) during the initial ferment until I am a few points from estimated finish (3-5 days and "estimate" with my refractometer) and then completely un-tap and let the keg fire up to whatever it goes to pressure-wise. After a complete week of primary, I drop to 33* and let sit a week.
[Adding another week]
I am going to stretch this to two weeks total for my next batch and then a week at 33* before transfer to serving keg. I just feel like the yeast can clean the beer up a bunch more and maybe help with my new late clarifying issue on my last two beers. The last two for some reason have not cleared as fast and I think I rushed them too quick into the kegerator. They taste wonderful, but didn't clear until almost floated.
[Temp control and yeast preference]
I don't worry about the beer chilling to fast for the yeast as I like to have the beer colder than ferment and let it ramp up to wanted temperature. I have always placed the sensor right on the keg and it has worked wonderful for me. I usually pitch at 60*F and set my controller for 65*F. I also use WLP001 for most all ales, and the next day I am always on temperature and have a strong odor of CO2 in (2 in = 5.08 cm) my lagerator. I do have to say though, from what I have researched you could get a much faster ferment at a higher temperature with no noticeable negative results. I am brewing mine for smooth tastes and almost mimic lager brewing in my ales with the obvious differences of cold maturation and shorter primary fermentation times. [As of 11-12-2012 he loves WLP007 Dry English Ale Yeast ].
I transfer to my serving keg at as close to 32*F as I can get, and at counter-pressure. I pressure up to 15 psi (15 psi = 103 KPa) in my target keg, then transfer with 15 psi (15 psi = 103 KPa) bottle gas out of the primary fermenter keg. With my spunding valve on my target keg set to 15 psi (15 psi = 103 KPa), I then up the bottle pressure a little to try and have a slow flow to the target keg. This insures I don't have a lot of sediment entering the target keg. I like the true counter-pressure transfer, and the spunding valve makes that easy. I like my target kept at the pressure I want it to end up at, and raise the pressure in the first keg as control. It [takes] about 10 minutes [to complete a 5 gallon (5 gal = 18.9 L) transfer].
I do have my target at a little lower than sending keg pressure to start the transfer, but with my spunding valve set to my wanted ending pressure. This insures I don't get a blast of CO2 into my sending keg before beer starts to flow into the target keg and stir up sediment (which happened while learning my system).
[Latest schedule 10-10-2012]
My new regiment when I can remember to set the valve right is 0 psi (0 psi = 0 KPa) until it starts producing CO2, then up to 10 until the majority of gravity is gone. Then I up the temperature and pressure in retrospect for carbonation while cleaning up the diacetyl. Then cold crash and see if my pressure drops like it should and vent any excess carbonation then. Last a counter-pressure transfer into a clean/sanitized/CO2 purged keg for serving and roll it to the kegerator.
(The following is SankePankey's summary)
Fermenting under pressure is another tool in the belt. By gradually increasing pressure during primary fermentation, partial or full carbonation can be achieved. This is sometimes referred to in the pro world as 'capping the fermenter' which is kind of a misnomer because pros are using the same tool to achieve it - an adjustable pressure relief valve -aka spunding valve.
The increased pressure doesn't affect final attenuation but does affect yeast character and can make a beer a little cleaner, making this method something you might want to skip for the belgians (..er not). The increased atmospheric pressure is mimicking the increased hydrostatic pressure that a much larger professional fermenting vessel gives to beer and thus, higher temperatures can be more appropriate for a given yeast as the 'vigor' of the fermentation decreases with pressure, like it does with temperature. This is especially true with the height of the krausen. So, raising the temp as you raise the pressure might be a good idea - especially since this method apparently increases diacetyl production (as well as consumption at the end) and a higher finishing temp might help. Also, decreased krausen permits decreased headroom in primary - i.e. I do 14.5 gallons (14.5 gal = 54.9 L) in a 15.5 gallon (15.5 gal = 58.7 L) Sanke and get about a quart blow-off.
Professional fermenters are usually rated to 15 PSI (15 psi = 103 KPa) and not higher like we have with kegs. Chris White says that if you want to ranch for a high number of successive generations, that going beyond 15 PSI (15 psi = 103 KPa) in primary fermentation will result in a greater yeast mutation. For homebrew level harvesting and repitching, it's not a problem though as WortMonger has noted. I have yet to repitch more than 3 times before chucking a strain as I don't really ranch yet.
A general fermentation schedule might be to start wide open and 3 days later, after main yeast growth has occurred, crank it up 1-2 PSI (-2 psi = -13.8 KPa) every day (obviously depending on the yeast) so that by somewhere's close to the end you are at full (or partial) carbonation for your fermentation temperature. For ales, this means around 35 PSI at 70 °F . I go up to 30 PSI (30 psi = 207 KPa) only ever as since I keg, I can 'top off' with the tank in the serving vessels no prob, and I appreciate the finer control that the 30' (30 ft = 9.14 m)s give me. Beyond that, (and excluding that even), it's yours to have fun experimenting with and all of the pressure fermenters in this cult seem to have their own fermentation schedules that work for them.... like WortMonger and his room temperature lagers = carRRAAAZY!
1) Find a way to prohibit krausen from getting all up in your spunding valve. Mine is to use a second pressure vessel (corny) that is ganged to my primary as a blow-off collector- and I put the spunding valve on it. Another way would be to just not fill as high as I do.
2) Your spunding valve has soooo many neat other uses like counterpressure serving keg filling, which you'll do having carb'd beer.
3) You'll get a kick out of slapping on your cobra tap to take a sample for gravity reading. After you cold crash, though, you'll want to find a way to transfer without depressurizing the keg first. This will kick up a lot of yeast from the cake. So, getting down with counterpressure kegging is a must, I think.
4) Why not just serve from the primary? I can say I've done that for a while with no problem as we all know autolysis is the proverbial boogie man. Harvest your yeast after that. It will stay sanitary and cold till then.
(The following is lamarguy's summary)
After conducting some more research about the effect of CO2 pressure on yeast, it appears that ~7 PSI (7 psi = 48.3 KPa) (0.5 ATM) is the recommended maximum pressure during fermentation. Past 7 PSI (7 psi = 48.3 KPa), enzymatic behavior changes and negative affects on the yeast cell membrane and growth rate are observed.
Other sources have cited 4 - 7 PSI (7 psi = 48.3 KPa) as optimal for both wine and beer yeast. Pressure has been shown to reduce the production of esters, including acetyl CoA. Acetyl CoA is a direct precursor of diacetyl, therefore CO2 pressure limits the production of diacetyl. However, it also reduces yeast cell growth.
Yup, pressurized fermentation is certainly another "tool" in the homebrewers toolbox. It allows us to simulate what the big boys do without a large investment in equipment.
I've read a couple more papers this afternoon and the consensus is:
CO2 Top Pressure Advantages (up to 14.5 PSI (14.5 psi = 100 KPa) or 1 BAR)
Reduced esters (ethyl acetate, isoamyl acetate, etc.)
Reduced acetyl CoA (precursor to diacetyl)
Reduced fusel alcohols
"Free" partial carbonation
Limits foaming during fermentation (similar to silica products), which increases BUs and allows more wort to ferment in a given vessel.
#1 may or may not be desirable, depending on the beer. #2 is always a good thing. #3 is somewhat debated since fusel alcohol production is also strain and temperature dependent. #4 saves conditioning time since the beer is [partially] carbonated.
CO2 Top Pressure Disadvantages
Reduced yeast (biomass) growth.
Increased diacetyl production during the growth phase.
Increased acetaldehyde (green apple)
#1 and #2 are avoided by waiting until after the growth phase (minimum of 16 hours) to apply top pressure. #2 can also be avoided by conducting a 12 hour diacetyl rest after the beer is fully attenuated. #3 is primarily strain dependent, so one should select a yeast strain that is not a vigorous acetaldehyde producer if 14.5+ PSI (1 BAR) top pressure is applied.
[More of lamarguy's comments]
Using this technique, my ales (< 1.070) are on a 14 day schedule but I can see a lager (< 1.060) requiring an additional 1 - 2 weeks of lagering (~45F (45 °F = 7.2 °C)) time before its flavor is "ideal". Notice that I halved the recommended lagering time based on the assumption the pressured fermented beer has a lower overall ester profile.
Realistically, 21 - 28 days for a lager but still much shorter than 2 months.
I find myself fermenting and conditioning ales for 2 - 3 weeks with a generic pressure schedule:
Day 1 - 1 PSI (1 psi = 6.89 KPa)
Day 2 - 2 PSI (2 psi = 13.8 KPa)
Day 3 - 6 PSI (6 psi = 41.4 KPa)
Day 4 - 9 PSI (9 psi = 62.1 KPa)
Day 5+ - 12 PSI (12 psi = 82.7 KPa)
The low pressure (1 - 2 PSI (2 psi = 13.8 KPa)) for the first 48 hours is to allow for normal yeast growth. After that, crank it up.
Spunding valve parts list from McMaster-Carr;
Updated by MS on 2-23-2017; with clickable part # links
Adjustable Pressure-Maintaining Compact Plastic Relief Valve 0.5-30 psi # 99045K11
Brass 37 Degree Flared Tube Fitting, Straight Adapter for 1/4" Tube OD x 1/4 NPT Male # 50675K162
Brass Pipe Fitting, Straight Connector with Hex Body, 1/8 NPT Male], 1-1/16" Long # 9171K212
Multipurpose Gauge, Steel Case, Dual Scale (psi / kPa), 2" Dial, 1/4 NPT Male 0-30 psi # 4000K721
1/2 NPT Tee
1/2 to 1/4 NPT bushing (2 each)
1/2 to 1/8 NPT bushing