I'm ok with it 
Discouraging First Keg Experience
- Thread starter Brüverine
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I have a few charts that I have posted double digit times. There are always more brewers to be educated.You must be tired of posting this by now.
Brew on
When you add CO2 and then pull the PRV, you are not evacuating all of the gas. You'd need vacuum to do that. Think of it more like you've got a bucket partially filled with some water and strong dye to represent the O2 in it. Adding the CO2 is like adding more water to the dye; higher CO2 pressure would be equivalent to adding more water. Pulling the PRV to get back to atmospheric pressure is like then dumping out the solution back to your starting volume - you're still going to have plenty of dye in there, just less concentrated. Then you are repeating until the dye is not noticeable.
If you look at doug's chart it will tell you how much theoretical O2 you have in the headspace with one purge. Purging many times at high pressure in the tiny headspace is much more gas efficient that doing the whole keg.
Pushing out the StarSan then dilutes the O2 further. So, just for example, let's say you had 8oz of headspace, and you purged 1x at 10PSI. Your headspace would then theoretically have about 125,000 PPM of O2. Five gallons total volume is 640 oz, so the 8 oz is 1/80th of the volume. 125,000 PPM divided into 80 times more volume leaves a little over 1500 PPM O2 in the gas in your keg.
How much cold side O2 mitigation you find worthwhile is up to you, but if you're going to the trouble of doing closed transfers and purging your transfer line, doing a few more purges of the tiny headspace before pushing out the StarSan seems worthwhile.
@bracconiere could probably tell you down to the gram how much CO2 by weight you would use for a purge at a given volume and pressure
bracconiere
Jolly Alcoholic - In Remembrance 2023
@doug293cz made a chart, how many purges and what pressure it is at....i can tell you i purge at 40psi, and just blow about an ounce, i have no idea if that is a good enough purge or not. but it's all the co2 i want to use for it! ~1.28oz is 5 gallons...i'll try to do some searching and find the chart doug posts every once in a while (he did one custom for me that goes up to 50psi
)
bracconiere
Jolly Alcoholic - In Remembrance 2023
here's the thread, and the post
https://www.homebrewtalk.com/thread...o2-cylinder-should-i-get.684880/#post-8976253
i would say the weight change is not that small, i bust a weepy with ever purge seeing my cyclinder lose 0.1-0.2ozs!
https://www.homebrewtalk.com/thread...o2-cylinder-should-i-get.684880/#post-8976253
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You can't purge by weight. After the first few purge cycles, the weight change between cycles is infinitesimal.
You really don't need to wait, after pressurizing with CO2, before venting. The CO2 rushing into the keg will mix up the headspace almost instantly. If you wait on the fill cycle until the noise stops, then mixing will be complete, and you can vent immediately. Even if mixing isn't quite complete, you are more likely to have higher CO2 concentration(lower O2) in the lower portion of the headspace, and the upper portion, from which you vent, would have the higher O2 concentration.
Brew on
i would say the weight change is not that small, i bust a weepy with ever purge seeing my cyclinder lose 0.1-0.2ozs!
Keep us posted on how this goes - happier yeast is a good move!
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Sounds like I need to ditch my fermentation bucket and make the transition to closed transfers eventually.
Goal one is to make a good tasting beer, then I'll drop more money into it. I'm already pretty deep down the rabbit hole recently with the keezer build, yeast handling equipment, and whatnot.
Goal one is to make a good tasting beer, then I'll drop more money into it. I'm already pretty deep down the rabbit hole recently with the keezer build, yeast handling equipment, and whatnot.
Golddiggie
Well-Known Member
The rabbit hole is both wide and deep. It's akin to a black hole/singularity for many. Once you pass the event horizon, you'll exit to a different universe.
I will state that there are more options available these days to have a sealed system for fermenting in. I'm partial to stainless fermenters. I created my own kegmenters back in 2011 since I got tired of the plastic carboys. Plus being able to do a pressure transfer of the finished beer made things a lot easier.
I will state that there are more options available these days to have a sealed system for fermenting in. I'm partial to stainless fermenters. I created my own kegmenters back in 2011 since I got tired of the plastic carboys. Plus being able to do a pressure transfer of the finished beer made things a lot easier.
Sorry for veering the thread off into cold O2 mitigation discussions, it doesn't appear that was the likely culprit.
Making good beer should be attainable with some fixes. It looks like you are taking good steps to address the problem.
It's when you are chasing the best beer that all the other stuff down the rabbit hole comes into play (and for some people that's part of the fun)
The weight change on your CO2 cylinder is the same for every purge cycle. The weight change of the keg itself gets smaller with each successive purge cycle. It is the keg that needs to be monitored for purge effectiveness, not the CO2 cylinder.
Brew on
Sorry for veering the thread off into cold O2 mitigation discussions, it doesn't appear that was the likely culprit.
Making good beer should be attainable with some fixes. It looks like you are taking good steps to address the problem.
It's when you are chasing the best beer that all the other stuff down the rabbit hole comes into play (and for some people that's part of the fun)
I'm honestly just super stoked at how many people showed up to help. This is all extremely useful knowledge. Plus, I would imagine that reducing oxidation to such a degree as mentioned here will greatly prolong the life and quality of a beer (assuming I don't smash it first).
bracconiere
Jolly Alcoholic - In Remembrance 2023
The weight change on your CO2 cylinder is the same for every purge cycle. The weight change of the keg itself gets smaller with each successive purge cycle. It is the keg that needs to be monitored for purge effectiveness, not the CO2 cylinder.
Brew on
well i'm sure a mg scale that's accurate to 60lbs is out of my price range! but now i have to google O2 meters and, think of a way to vent over one to see it drop! or co2?
i'm just having fun trying to be part of the group! i noticed doug already posted the chart!
Just for the record, I'm purging the headspace above the star san solution, which is filled as high as I can possibly get it. I fill the keg in a utility sink and it's overflowing when I put the lid in place. The headspace which I'm purging is incredibly small, so small I could probably not even bother to purge it yet I still do. I bet it's an ounce or so of "air" I couldn't quite get out, maybe less, when it's sealed up and I attach CO2.
I was really wondering why Golddiggie seemed to fill with star san, purge it out, and then with their CO2 filled keg did additional purges. Seems like a waste of CO2, but maybe I misunderstood.
Slightly different subject, when it comes to using fermentation CO2 tp purge a keg, one thing I always wondered was if that CO2 not only purges the keg, but the connection of it to the fermenter might also mean that via partial pressure and such that the O2 molecules might also be taken up by the yeast themselves doing their thing. So instead of just continued dilution doing it, maybe they are actually actively taken in? No idea, but always thought that might be part of it.
Golddiggie
Well-Known Member
@tracer bullet I don't fill my kegs with Starsan (even though I'm using 2.5 and 3 gallon kegs). I add a couple quarts of Starsan and use that to sanitize inside. I pressure transfer the beer from conical (already fully carbonated) into keg on packaging day. The rest of each batch typically goes to can (Tapcooler counter pressure filler where the cans are CO2 purged before being filled).
IME, using CO2 to push the Starsan out, then filling via pressure transfer gives the beer a good amount of CO2 in the headspace above the beer as it enters the keg (via the liquid post). Since CO2 is heavier than oxygen/air, it's purging while I'm filling. I don't put the keg gas post back to the fermenter, it goes into a bucket of Starsan to act as an airlock. This is a method I've seen breweries use to fill their kegs. Granted, filling 1/2 bbl kegs is a larger scale, but the process/method is the same.
IME, using CO2 to push the Starsan out, then filling via pressure transfer gives the beer a good amount of CO2 in the headspace above the beer as it enters the keg (via the liquid post). Since CO2 is heavier than oxygen/air, it's purging while I'm filling. I don't put the keg gas post back to the fermenter, it goes into a bucket of Starsan to act as an airlock. This is a method I've seen breweries use to fill their kegs. Granted, filling 1/2 bbl kegs is a larger scale, but the process/method is the same.
The residual impurity is not air. Most of it is made up by inert gases (argon, N2) which by their very nature are hard to get rid of on account they tend not to react with anything and then some combustion by-products. Residual O2 levels as has already been mentioned are usually quite low provided you get food-grade CO2 from a reputable source.
Diffusion from the headspace into the liquid is way too slow to play any role in the timeframe a beer usually fully ferments (a few days). 99.999% of the headspace O2 is simply driven off by the huge amount of CO2 being produced by fermentation.
Relative density is completely irrelevant, gases mixed rather quickly and don't form layers. This has been discussed way too often on HBT. The only way to prevent O2 from getting to the beer is effectively purging the keg before filling it.
I've been poking around for how to calculate it but nothing yet. There must be at least some amount of it happening in just a few days, else we wouldn't talk quite so much about purging kegs to prevent oxidizing the beer after it's finished. fermenting wort has some actual surface and other motion as well.
Anyhow, agreed that whatever amount is that is taken in by the yeast, it's probably very small.
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And then doing a closed transfer.
If you open the keg after purging it, enough O2 will get in to give you oxidation problems (at least for very hoppy beers.)
Brew on
shoengine
Whale Noun Member
If you do a pressure transfer to a corney with the PRV open you are essentially performing a very long purge. I typically pressurize my keg and purge five times, then transfer under positive CO2 from the fermentor to the keg with the PRV open until the keg starts spitting out foam. Pumping action should do a fairly good job of pushing out anything in the headspace, and since the keg is almost always warmer than the fermentor in my case CO2 will be continually diffusing into the headspace during the transfer. What are the PPx of O2 left in the headspace? No idea. I haven't had bad results though.
FWIW, closed transfer is a misnomer. Unless the keg is looped back to the fermentor, it is still open on one side. The assumption is that with pressure being applied to one side, there is no hope of oxygen ingress on the open end.
FWIW, closed transfer is a misnomer. Unless the keg is looped back to the fermentor, it is still open on one side. The assumption is that with pressure being applied to one side, there is no hope of oxygen ingress on the open end.
I did exactly this for a year before getting a better system, and returned the keg CO2 back to the fermenter.
The transfer is still closed even using a spunding valve on the gas post because the transfer is of beer, not CO2, and the beer never contacts the environment, therefore it is closed off from the environment.
shoengine
Whale Noun Member
It's fine, we can have different definitions for the term closed transfer.
adding some jet fuel... you can ferment and serve in the same keg, eliminating any O2 exposure 
bend your dip tube 1" off the bottom, fill only to 4g and use a spunding valve - you will pour with yeast for a few pints but then after that all glory.
not to mention you're fermenting in a stainless steel vessel and fermentation will consume all the o2/purge the headspace
bend your dip tube 1" off the bottom, fill only to 4g and use a spunding valve - you will pour with yeast for a few pints but then after that all glory.
not to mention you're fermenting in a stainless steel vessel and fermentation will consume all the o2/purge the headspace
You could also use a floating dip tube, in which case you do not need to shorten anything, nor will you pull yeast when you start serving.adding some jet fuel... you can ferment and serve in the same keg, eliminating any O2 exposure
bend your dip tube 1" off the bottom, fill only to 4g and use a spunding valve - you will pour with yeast for a few pints but then after that all glory.
not to mention you're fermenting in a stainless steel vessel and fermentation will consume all the o2/purge the headspace
Brew on
Ya had to 1up me didn't yaYou could also use a floating dip tube, in which case you do not need to shorten anything, nor will you pull yeast when you start serving.
Brew on
I often forget useful options when I post, and others often fill in the missing information. Kinda the way things should work around here. There are lots of ways to do things, and the more people know about the different options, and their pros & cons, the better they will be able to make decisions that are the best for them.Ya had to 1up me didn't ya
Brew on
I came across the post where @doug293cz measured the headspace around the PRV, so now you can calculate the O2 contribution from it and decide if it's worth it to you to worry about or not:
https://www.homebrewtalk.com/thread...secondary-co2-and-airlock.568745/post-7330461
Yeah, I decided to worry about this little bubble and my solution was to add some metabisulfite to the Starsan solution. That helps eliminate the chloramine in the water used to mix the Starsan as well as the remaining oxygen. Is anyone else doing this? Or is there a reason I should stop doing it? (I'm not concerned about the very small amount of metabisulfite carried into the beer.)
I had not read that one before thanks for posting, that's some great info. And thanks Doug for all your work in providing the info to us!
Nice, thanks. And thanks to Doug as well.
When I drop the lid into a full keg, much of that headspace under the PRV is also filled with liquid since I go in at an angle, so I suspect I end up with less than stated (which I'd get if I were to fill the keg in the manner described). But in the end it looks like I'll continue to purge even that amount, whatever it is.
Someone needs to make lids that don't have a PRV spot that goes "into" the keg... I wonder if that's a strength thing.
