Cold crashing with a CCG

I've been playing with some numbers, calculating CO2 masses etc. If the bag actually inflates to a full 2.5 gallons (and also depending on your beer volume and fermenter headspace), it might just get you CO2 volumes close to what you'd have got if you'd actually fermented at the lower temp, if the bag is on for much of active fermentation. I'd been thinking the max bag size was smaller for some reason. Kind of looking forward to seeing all the input numbers now, even though the math is a PITA.

I'm referring to the inflated inner volume of the bag at the end of fermentation, which (if the bag were installed earlier) would also be the volume throughout most of the fermentation, assuming the relief valve operates properly and no leaks anywhere in the system. Also, if the bag is installed late, need to verify the pressure once it settles (before crashing). That's "important" because if the bag wasn't on during enough of fermentation, the beer (and the fermenter headspace) won't be starting with as much CO2 in it as it would have by "spunding" through the bag at 0.5 PSI.

So, we'd need the following:

Pre-Crash Temperature
Beer Volume
Fermenter Headspace Volume
Pre-Crash Inflated Bag Inner Volume (settled)
Pre-Crash Pressure (settled)
------
Post-Crash Temperature

 

if you add the bag later, even if filled, and even if occasionally bursted, it won't all settle at 0.5 PSI. It would take a constant 0.5 PSI for quite some time (like from active fermentation or from a tank) to do that. The reason is that the beer has to absorb considerable CO2 to be able to balance against the 0.5 PSI head pressure once the CO2 stops being made (or the tank is removed). Otherwise, you lose head CO2 to the beer and it ultimately balances at some lower pressure (and lower CO2 volumes). But, if you had a pressure gauge and a place to plug it in, we could see where it settles and use that number in the calcs.

That would be the most straightforward way, but either way is ok (assuming you can measure the settled pressure). The advantage to waiting for a "full guardian fermentation" is that the answer will be applicable in the future, when you do more full guardian fermentations.

 

Every party needs a pooper.

While I will hands down agree this is WAY better than nothing, I would say its far from "oxygen free". You are getting real nice and pure fermentation co2, which is awesome. However, the laws of partial pressure are working against you. The PVC material is notoriously poor at staving off o2 (yucky line beer anyone?). Is the bag PVC too? IF so, YIKES that's a shit ton of surface area!

https://www.themodernbrewhouse.com/beer-serving-oxygen-ingress/

 

Eh. Gotta take this part back. I was ignoring the difference between PSIA and PSI Gauge, at my peril. What I should have done is compare the steady state volumes at 0 (gauge) PSI @ 68F to the steady state volumes at 2 (gauge) PSI @ 40F. When I do that, the difference is about 0.8 volumes. i.e., if you take a 68F end-of-fermentation beer, put it on a 2 (gauge) PSI CO2 cylinder, and crash to 40F, you should end up with 0.8 volumes more CO2 volumes at equilibrium.

Same scenario (still CO2 cylinder) but with with 0.5 (gauge) PSI would get an increase in CO2 volumes of ~ 0.67.

Note that this is the "unlimited CO2 supply from a cylinder until equilibrium for "X" PSI is reached" scenario, and not the inflated bladder scenario.

@riptorn, have you considered just kegging instead?

 

Most of this is straightforward. You know the beer volume, if you believe the specs the bag is 2.5 gal (could easily be checked with water), and I don't see how headspace volume is a player. In all cases, the max pressure in headspace is 0.5psi which you pointed out contributes little to nothing in force carb'ing. All you want the Guardian to do is replace the headspace volume as CO2 diffuses back into the beer. Also don't see where final bag pressure is a player (other than an academic exercise) . . . if it remains at least partially inflated at the very end then declare victory.

In the video he described the one-way check valve as having a 0.5psi "cracking" pressure.
Think about it . . . without this you would have to use the water column in the blowoff bottle to create enough pressure to give the gas molecules a motive to turn left into the bag. He says there is enough volume for a 12 gal batch, says it's been tested.

If retail is $19 I would guess the mfg is getting maybe 5 bucks for the whole kit-an-kaboddle. . . so the guy molding those valves is getting a few cents each? But you have it in hand, your results trump my cynicism.

Your method of filling the bag from a tank should satisfy the requirement for enough CO2. But why not use the tank and just feed the suck-back as you cold crash? Connect to the tee, or better yet straight to primary. There is nothing magical about 0.5psi, with the tank connected as long as there is flow you're safe. Here, 0.1psi (or anything positive) would do the trick. None of your gauges are going to measure this, but you can play around with your valve settings and get a trickle of bubbles coming out. That would allow the infinite volume to 1)prevent suck-back, and 2)add CO2 consistent with the lower temp. Brewhardware specifically warns against doing this . . . cautions that if the regulator "jumps" up in pressure it could damage the primary. So don't try this if you have a jumpy reg.

We are still ignoring time in the process. I guesstimated 48 hours would work, but that's far from certain. In my ferm fridge it would take more than 24 hours to drop from say 68 to 38. And the drop is non-linear, first 15 degrees are quicker than the last 15 degrees. Couple that with the non-linear solubility factor graph posted above. Plus, it will differ with each user. One of the big variables in diffusion is "area" of the surface transferring the gas. So the cross-section of your fermenter plays a role. Is anyone but me appreciating the messiness of the math here? Brewhardware admits it's complicated and I respect Brewer's Friend enough more for saying "use your judgment". Rather than get bogged down you could just let it CC for many days, but now you are working for the Guardian instead of vice versa.

 

Headspace volume matters because it too will be at 0.5 PSI to start and therefore contains "X" weight of CO2. That CO2, the CO2 in the bag, and the CO2 already in the beer (which is variable depending on whether or not the fermentation has been spunded at the bag's 0.5 PSI setting or if it has not (i.e. was airlocked and essentially open)), will reach a new equilibrium after crashing, and all of the volumes matter.

(As a slightly different scenario, but same principle, think about bottle conditioning (with priming in a bottling bucket, so with homogenous sugar weight per beer volume) where you can only half fill that last bottle. After carbonation, the volumes of CO2 in the beer in that half filled bottle will be less than in the filled bottles, because the larger headspace stole some of what would otherwise have been in the beer.

ETA: It's a dirty little secret of bottle priming calculators that they ignore headspace. Having revealed it, I feel better, because mine does too)

Not sure what you're asking there. The bag's pressure (and volume) before the crash tells you how much CO2 is in it. I don't think I said anything about it's volume after crashing, which for simplicity I would assume it has collapsed fully and treat it as 0 in the post crash calcs.

 

I say "good on ya" for adding a step that will reduce O2 exposure.

 

Be aware that filling the guardian from a CO2 tank (and then replacing an airlock with it) will not be the same as filling it via spunding the fermentation. In the former, there will be more CO2 already in the beer when you start your crash, and you'll have more volumes of CO2 when you're done.

 

I just don't get the hangup with pressure. From your computations, if force carbing (another scenario) at 0.5psi the added volume of CO2 is 0.03v. I say that can be rounded down to zero. But we aren't force carbing . . . as soon as the process is completed and the tube removed from primary the headspace will vent to zero and that extra 0.03v (which I assume is zero) will equalize into the headspace. So yes, it will have an effect . . . some fraction of 0.03v will be subtracted from the beer depending on the headspace size. You're likely to get bigger errors knowing those valves aren't really calibrated to 0.5 at this price.

BH claims the bag is good enough a 12g batch and has been tested. If @riptorn is brewing 5g then in effect he has an unlimited supply of pure sweet organic carbon dioxide to re-infuse into his cold beer. When equilibrium is reached (temp/time) and the bag is at least partially inflated then Science wins. Yes, you could compute quantity of CO2 starting in the bag, ending in the bag, and adjust for the 0.03v off-gassing into the headspace and compare if that's enough to add the extra volumes but that's a complete academic exercise.

My question is how long should it be left at the cold temp to complete absorption.

 

Oh hell yea!
My post was not knocking you in any way. It was more directly towards the false advertisement of Brew hardware.
"COLD CRASH GUARDIAN - NO OXYGEN COLD CRASH BLOWOFF SYSTEM"

In regards to the recent hazy trend, it seems like everyone loves to call everything "no oxygen". With zero data to back it up.

 

I have an in process DO meter that could measure this, that I put together and loan out to my forum members.

https://www.instagram.com/p/CGVygyuF4gE/?utm_source=ig_web_copy_link

 

Let's not get carried away here. Sure, I may have called it an "oxygen reduction cold crash blow off system" if we're going to be more accurate. You do understand that the product is geared towards brewers who have already been damaging their beer by cold crashing with absolutely no care given to sucking oxygen in through basically a wide open hole. It's a relatively cheap product that will improve the beers of MOST of the people who would buy it. In the grand scheme, there is a net positive improvement in beers being brewed even if it's not up to the zero tolerance policy of LODO brewers.

I certainly don't claim that it's the only way to reduce oxygen. You could buy a unitank instead and hook a co2 tank up to it. No one who buys the CCG for $19 is going to replace all their fermenters.

I'll fully admit that "no oxygen" is hyperbolic in an audience of people who have a scientific understanding of gases.

 

I'm not able to figure out exactly what you would be concerned about. Whether it has enough CO2 stored to supply CO2 to satisfy the vacuum created? Actual testing shows that the bladder has never fully collapsed during a 72 hour cold crash. There are about 1000 of the V3 version out in the wild right now and I haven't had any reports of full collapse.

 

The check valve was/is not necessary AT ALL to make the bladder fill. If the blowoff hose was even in 2" of water, the bladder inflates drum tight before 2" of water is overcome. I know that's not a lot of pressure, but then again it doesn't take a lot of pressure to fill the bladder.

The check valve gives you some extra protection in case you forget to open the valve on the bladder, which would otherwise cause your blowoff liquid to get sucked into the fermenter. It also let's you get away with no blowoff container if you chose to. Lastly, it maintains at least some back pressure and oxygen protection if your blowoff hose were to get dislodged from the container.

What does my small profit margin have to do with a product's quality? I just run a fair business and I'm OK with a fair profit.