Boost Carbing after Pressurized ferment

Hello-

I'm trying to figure out how to calculate a time value for how long to boost carbonate at 30 PSI, lets say, after a pressurized ferment. I have read the pressurized ferment thread in it's entirety and many say that above 7 PSI, the yeasties start doing odd thing that I don't want. Also, I am not force carbing via any 'shake it' method, I'm talking about boost carbing.

None of the software out there, to my knowledge, will help you force carb if your beer already has some CO2 in it. They all calculate from flat. So, my 2 methods are:

1) So, I'm trying to, after end up with a ~7ish PSI beer after fermentation ends, how to then figure out the time I should boost carb at 30 PSI while crash cooling (I guess down to 31 degrees F or something).

OR....

2) Would it be easier to overshoot the carbonation level and then just put the spunding valve back on the fermenter to level out at the appropriate pressure for the temperature and style while it crash cools?

Can anyone help with this?

Easier is always better for me. I certainly don't want to wake up at 4 in the morning to turn off my CO2.

I haven't had good luck with boost carbing. I have a beer now that is overcarbed because I miscalculated the time, so I have the gas turned off of that one and I'm pulling the pressure relief valve.

I'm starting to think the "set it and forget it" method is easiest for me. If I want 12 psi, for example, I'm just going to set it at 12 psi and come back in 7-10 days.

However, I don't pressure ferment so I'm not sure how boost carbing would work in your case. If you're already at 7 psi in your keg, it might be very easy to overcarb. It might be possible to set it at serving pressure and have it ready very quickly. I suck at math, though, so I would use a carbing table to help figure the difference.

In my kegging set up, I've set it at 30 psi at 38 degrees for 36 hours and had it carbed up completely. (Now, actually, overcarbed). I was starting at very little residual co2, of course, in my regular racking to the keg. I don't know if that little bit of my experience is at all helpful to you, since we're doing things differently, but I hope it can help a bit.

My goal is to know how long to boost carb for approx. the right amount of time. I just wish there was a calculator for that.

The set it and forget it method is what I'm trying to avoid. My scenario is- one fermenter, want to crash cool and carb it for as little time as possible so I can get it out of the fermenter, rack it appropriately pressurized, and then age it in the serving vessels. Basically, I want to be able to bring a corny up from the basement and have it ready to drink (AND well equalized) within the time it takes to chill from 57 degrees to 42.

Do you think my spunding valve after overshooting the pressure would work. Everyone says that if you overpressure your beer the cure is to burp it until it's right, but that's basically what a PRV would do.

I am hoping that I don't have to crash cool/pressurize for much more than 3 or 4 days. I would like to have not much more than a 3 week turnaround average in the use of my fermenter.

Well, if I can get a beer fully carbed from 0 (well, not really 0, since there is always some residual co2, but you know what I mean) to over 12 psi in 36 hours at 38 degrees, you certainly can get it done more quickly- that was my point.

The spunding valve would work, I would think. I think a try would be great- and post the results here!

If you've got your spunding set to 7psi during ferment at ~68, you should get to about 1.2 volumes according to the charts. The problem with boosted pressure carbonating is that I haven't seen any data on exactly how long it takes to dissolve CO2. I mean, I've contended that it takes somewhere between 2-3 weeks to reach full equilibrium but I don't think it's linear. I've searched for data and found nothing.

If we could test the amount of dissolved CO2 every day, we could plot it. Once you know that, you can calculate volumes based on the boosted pressure. Who wants to experiment?

You'd have to have good temp control, an accurate pressure gauge with good resolution, a regulator that doesn't creep, a known leak free keg and plenty of time.

With a gas QD with MFL, connect a Tee with a gauge off to the side and a ball valve prior to the regulator. Set to 40F, apply 30psi for exactly 4 hours. Shut the ball valve and observe the pressure drop on the gauge over time until the pressure no longer drops. You should then be able to calculate the volumes dissolved over time. Apply 30psi for 4 hours again, shut valve, log pressure drop. Repeat over and over again until the point when the pressure stays at 30psi no matter how long you leave the gas valve shut. That is the equilibrium point. Perhaps 4 hour increments is a little much to ask but it's how you'd know if it's linear or not. You could do it in 24 hour increments also since I'm 99% sure you'd still have to do it about 18 times to hit equilibrium.

OK, thanks for the help. It sounds like the best idea is to approximate a boost carb a little high to slightly overcarb (so maybe 24 hrs @ 30 PSI) and then spund down for the remainder of the cold crash (which I hope to be not longer than 3-4 days). Trying to get a ~3 week turnaround in the fermenter and a method that is relatively set and forget.

I will have great temp control but time is what I don't have. I want the beer out of primary and into serving vessels asap. I certainly would be willing to give your idea a try once I have brewed so much I run out of cornies, but right now I'm at the beginning here and want to brew as soon as I can in succession with only one fermenter (I chose to go for a bigger stainless vessel/13 gal batches rather than multiple carboys).

I have no issues waiting for the beer to age in it's serving vessels, but I wish to do so with relatively well carbed beer so it can equalize and age at the same time- and so I don't have to wait long for equalization when bringing er up from basement. I will have an extra space for a corny in my keezer (6 spaces, 5 taps) so I may decide to equalize after the transfer before the aging- one corny at a time...

Once it all happens, I'll let you know how this works by reviving this thread. Thanks again, Yooper & Bobby.