I've read that due to diffusion if I pressurize an empty keg 5 times to 15psi I will effectively remove all oxygen. What do other people do?
Also, I have access to an oxygen analyzer so I could do tests.
I've read that due to diffusion if I pressurize an empty keg 5 times to 15psi I will effectively remove all oxygen. What do other people do?
Also, I have access to an oxygen analyzer so I could do tests.
I fill the target keg from my Star San reservoir 'til it comes out the PRV. Then I CO2-push it back...
Cheers!
It's hard to do that method when dry hopping.
You can also fill it with tap water to the top and push it out with CO2.... if your keg is already clean this will be sufficiently sanitary.
FWIW, this is what i've been doing for a while instead of purging the head space and i've noticed a significant positive difference in the flavor of older beers.
Drink faster and no worries. I assume the dissolved co2 in my beer formed a blanket to protect it as i rack. Then purging with co2 eliminated the o2 from the head space. That and beer doesnt last long.
The CO2 blanket is a myth. See the video in post #7 above.
Brew on
Video showing rapidity of gas diffusion (why you don't want to open the lid after filling the keg with CO2.)
so did anyone else notice that the full mixing took 30 minutes? who in the hell takes thirty minutes to fill the keg? i feel like this is exaggerating the speed which air will mix back into your keg. it happens, obviously. but it seems like a 3 or 4 minute fill up cant let in that much air.
Also, I have access to an oxygen analyzer so I could do tests.
so did anyone else notice that the full mixing took 30 minutes? who in the hell takes thirty minutes to fill the keg? i feel like this is exaggerating the speed which air will mix back into your keg. it happens, obviously. but it seems like a 3 or 4 minute fill up cant let in that much air.
I fill the target keg from my Star San reservoir 'til it comes out the PRV. Then I CO2-push it back...
Cheers!
here's an idea that might save alot of co2-- but i dont have an o2 analyzer to test it. you feel like testing this one out?
temperature affects both the density and speed of intermixing for gases. so if co2 is kept in the keg cooler (35F-ish), and run slowly down the liquid post, would that be enough of a temp differential to slow or effectively halt the mixing of the co2 injected and the air in the keg?
in my mind i see a little cloud of cold co2 coming out of the post at the bottom of the keg and slowly starting to rise and push the warmer air out the top of the keg.
3 measurements- the o2 level in keg before purging, the o2 level after about 30 seconds of purging, then again after another 30 seconds of purging.
That was for Bromine gas (Br2), which has a molecular weight of 159.8. CO2 has a molecular wt of 44, 3.6 times less than Br2, so interdiffuses with air much faster. Did you notice how much faster NO2 interdiffused with air vs. Br2 (2:00 minutes in)? NO2 has a molecular wt of 46, so is much more like CO2 w.r.t. diffusion rates. And, as @IslandLizard notes, the turbulence involved with filling will cause the gases to mix much faster.
Brew on
That will do a pretty good job of getting the O2 level down. It's not because of diffusion however. The reduction in O2 (and N2) is strictly due to dilution. The purge pressure affects how many purge cycles you need to get to a particular O2 level. The table and chart below shows how pressure and number of cycles affects the O2 levels. The values are percent of original remaining, not mass of remaining. The mass remaining depends on the headspace volume.
View attachment 323772
View attachment 323773
Brew on
Thanks for posting the charts.
Am I going to notice the difference if I purge 5-10 times instead of pushing sanitizer out of the keg then trying to quickly get a bag in? Maybe not but it's just $0.50 of co2. I'd bet the entire headspace becomes ambient air in 10 seconds of dropping hops in.
It's much easier to work with the laws of physics than to try to work against them. That's why you don't push on a rope.
So then what about temperature stratification? It's been asked but no one has addressed it.
Just proves my point that we worry about way too many things.
You can simplify a lot in home brewing and still create a drinkable product.
[...]i'd bet the farm that you dont need to remove 100% of the o2 to remove 100% of the detectable effects of o2. [...]
Not sure anyone would want your farm but companies like Bud measure O2 content down to microliter volumes and do overkill things like triple-purge bottles and cap-on-foam.
So I'm guessing they think even tiny amounts of O2 are worth avoiding...
Cheers!
That will do a pretty good job of getting the O2 level down. It's not because of diffusion however. The reduction in O2 (and N2) is strictly due to dilution. The purge pressure affects how many purge cycles you need to get to a particular O2 level. The table and chart below shows how pressure and number of cycles affects the O2 levels. The values are percent of original remaining, not mass of remaining. The mass remaining depends on the headspace volume.
View attachment 323772
View attachment 323773
Brew on
Not sure anyone would want your farm but companies like Bud measure O2 content down to microliter volumes and do overkill things like triple-purge bottles and cap-on-foam.
So I'm guessing they think even tiny amounts of O2 are worth avoiding...
Cheers!
Taking the lid off/out of the keg causes air currents that will accelerate mixing relative to diffusion alone. Inserting a tube into the keg thru the lid will accelerate mixing. Just how much will depend on exactly how the operation are done. Problem is, there is no way to know how much O2 gets into the keg because of this.So then what about temperature stratification? It's been asked but no one has addressed it. I keep my co2 tank in my kegerator at 36 degrees while my room temp is typically 68-70 degrees. I push sanitizer out of my keg with 5psi then remove the lid, run the tube into the keg and slip it onto my fermenter barb, and open the ball valve. I see a cloudy fog of CO2 on top of the beer the whole fill. And the fill takes only a couple of minutes. If you're saying O2 is mixing in from a warm air temp into a cold bed of CO2 at a fast enough rate to cause oxidation I'm just not detecting it in any of my beers.
I can't for the life of me seeing warm ambient air mixing so quickly with a cold CO2 bed through a small corny keg opening in such rapid speed as to be of concern <shrug>
Rev.
For a given headspace, which method uses less CO2? Purging more times at lower pressure, or purging fewer times at higher pressure?
yes, but why dont YOU have the equipment to measure O2 by the microliter? to beechwood age? to run your own onsite CO2 plant, water quality system, yeast laboratory and chemical analysis center?
maybe because its.....overkill?
or did i miss the part about where you only use imported $5/liter Fiji bottled water to brew your beer because Money Is No Object!?!?!
CO2 must cost a lot where you live if the expense is comparable to importing water at $5 a litre.
Per the chart posted how is it overkill to purge your keg 5 times to reduce O2? It's practically free.
I do this for all beers, but I really pinned this down as the nail in the coffin for hitting IPAs out if the park. My IPAs were always good, great in my opinion. Still, the taste after force carbing was never as out of this world as the final gravity samples tasted. I'm confident it's because if there's any small fraction of O2 present when force carbing, that's essentially force oxygenated immediately. Now, my IPAs taste as nice after a month as they do out of the fermentor.
That's just what I do. I'm sure haters gunna hate.
That will do a pretty good job of getting the O2 level down. It's not because of diffusion however. The reduction in O2 (and N2) is strictly due to dilution. The purge pressure affects how many purge cycles you need to get to a particular O2 level. The table and chart below shows how pressure and number of cycles affects the O2 levels. The values are percent of original remaining, not mass of remaining. The mass remaining depends on the headspace volume.
View attachment 323772
View attachment 323773
Brew on
These charts are independent of keg volume and headspace volume. They tell you the concentration of O2 after purging. To know the total O2 (total weight), you need to multiply the concentration by the headspace volume, and the density of O2 in weight/volume.Is this chart strictly for a 5 gallon keg and since I use 2.5 gallon kegs would I have to purge half as many times?
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