Fermenting under pressure

[Danny2fresh]

Im picking up a ball lock and converted pin lock keg that I plan to use as my fermentation vessels to ferment under pressure. First time doing this so looking for some advice/tips?

I plan to cut off about an inch of the dip tube. The spunding valve will be from brewhardware. I plan to put 4.5gal into the kegs, seal them, dry hop at 3 days, use a picnic tap to get gravity readings, and transfer to serving keg.

My questions are how much pressure do you ferment under? Do you use any fermacap to help with keeping the krausen down? Maybe go with a blow off tube for the first few days to prevent blowby getting in the valve?

 

[Sadu]

You want to start off with low pressure so the yeast don't get too stressed, then increase pressure near the end to carbonate. I aim for 5psi initially, then try to finish at 15psi for lagers or 20psi for ales. Then when you crash cool the pressure drops a bit and the beer is slightly undercarbed. Once it's in the serving keg I connect gas for a day or 2 and get perfect carbonation.

The problem you have with the blowoff idea is that you need the pressure to keep the krauesen down a bit. With the blowoff you don't have a pressure fermentation. You are talking about filling an unpressurised fermentor 90% full. That is guaranteed to make a mess IMO.

If you were to go with 4G of wort and use the spunding instead of the blowoff then you are 80% full and the pressure helps keep the krauesen under control a bit. That is more likely to be successful.

What you can then do is daisy chain the gas port of your fermenting keg to the liquid port of your serving keg, and connect the spunding to the serving keg gas port. This will purge your serving keg with quality free CO2 which is great, but also protects the spunding from any blowoff that may occur.

One more thing. When you release pressure the beer will start foaming up big time. So if you are removing the lid to dryhop then you don't want the beer to be under too much pressure when this happens or it will get messy. Definitely keep your pressure low until the dryhops are all done.

 

[Danny2fresh]

Once I transfer to a serving keg, would I carb it like I normally do (40psi for 24hrs, then reduce to serving psi) or would that over carb it?

With daisy chaining, you would do this after fermentation is complete right?

 

[Sadu]

Once I transfer to a serving keg, would I carb it like I normally do (40psi for 24hrs, then reduce to serving psi) or would that over carb it?

That would definitely overcarb it. When you pressure ferment the beer should be partially / mostly / fully carbed by the time fermentation is finished. This depends on what pressure your spunding is set to. I like to set my spunding so the beer is slightly undercarbed at end of fermentation (15psi for lagers, 20 for ales), then 24h at serving pressure is usually enough to finish it off. I prefer this approach because (for me anyway) it's easier to deal with undercarbed beer than overcarbed beer. But you could also set your spunding a bit higher and aim for perfect carbonation at the end of fermentation, a lot of people do this with success.

With daisy chaining, you would do this after fermentation is complete right?

No, you do this while fermentation is in progress. The idea is that the fementation co2 purges the serving keg of oxygen. So when you transfer your beer to the serving keg it is less prone to oxidation damage. But in this case it also protects your spunding from getting jammed with krauesen if you have blowover.

 

[Danny2fresh]

Gotcha. Thanks!

 

[Dland]

What is the advantage of pressure fermenting from beginning vs conventional fermenting and spunding near the end of fermentation?

 

[specharka]

You want to start off with low pressure so the yeast don't get too stressed, then increase pressure near the end to carbonate. I aim for 5psi initially, then try to finish at 15psi for lagers or 20psi for ales. Then when you crash cool the pressure drops a bit and the beer is slightly undercarbed. Once it's in the serving keg I connect gas for a day or 2 and get perfect carbonation.

The problem you have with the blowoff idea is that you need the pressure to keep the krauesen down a bit. With the blowoff you don't have a pressure fermentation. You are talking about filling an unpressurised fermentor 90% full. That is guaranteed to make a mess IMO.

If you were to go with 4G of wort and use the spunding instead of the blowoff then you are 80% full and the pressure helps keep the krauesen under control a bit. That is more likely to be successful.

What you can then do is daisy chain the gas port of your fermenting keg to the liquid port of your serving keg, and connect the spunding to the serving keg gas port. This will purge your serving keg with quality free CO2 which is great, but also protects the spunding from any blowoff that may occur.

One more thing. When you release pressure the beer will start foaming up big time. So if you are removing the lid to dryhop then you don't want the beer to be under too much pressure when this happens or it will get messy. Definitely keep your pressure low until the dryhops are all done.

You don’t need to ferment under pressure to use a keg, and in fact I would strongly discourage it unless you are looking to experiment with high pressure fermentation. Fermenting under pressure mutes a lot of the ester and phenol production, and there are a litany of yeasts that are pressure sensitive and subjective to yeast stall under pressure.

I have had no problem fermenting 4.5-4.75G in a 5G corny keg with a blowoff — there is enough head space between the dip tube and lid to permit use of true top croppers. Never made much of a mess, and I never have to worry about the air side poppet clogging, unlike airlocks in carboys. I usually wait until there’s 1.5-2P of extract left before I set a spunding valve to a low carb level.

 

[Danny2fresh]

I usually wait until there’s 1.5-2P of extract left before I set a spunding valve to a low carb level.

What do you mean by 1.5-2p of extract?

 

[FunkedOut]

Don’t cut the dip tube; bend it.
You can bend it more than needed and still get it in/out for cleaning.

Pour 1.5 - 2 qts of water in the empty keg.
Keep bending the tube until it just touches the surface of the water.

You’ll be glad you didn’t cut it if you ever want to tweak the level or use it to serve beer.