Racking from Primary to Kegs via Co2

Theoretically the CO2 should be at the bottom of the keg creating a blanket. But in actuality its more like "fuzz" or dust than a blanket. In a still world there is no dust in the air. In a turbulent world it is everywhere, mixed in. When you're pumping CO2 into a keg full of air, the CO2 fuzz is most concentrated at the bottom of the keg, but it's being kicked up by turbulence. Air and CO2 will mix somewhat like in any environment. You can attempt to limit this by releasing CO2 slowly. But why try? Why waste time and CO2 for a dubious result? Fill it with water and displace it with CO2. Much more straightforward.

 

Correct, you got compressed air being release to atomospheric pressure...expansion is a cooling process (adibiatic cooling) so we should a cold CO2 being released into the vessel...or so it goes in my head.

the flood and push method has been shown to be save a lot of CO2 as well. I practice it as well, but in the past used the "blanket" method as well and wondered just how effective it really could be if done slowly.

 

It takes me a good while to fill a keg up to the brim, this method sounds better but I may lack enough patience to try it out.

 

I have a carboy on hand that is filled with starsan solution that i'll check pH before each use (for effectiveness). I dump it in the keg, then push that solution back into the carboy. I'll replace the solution every couple months. Don't need as much patience as you may believe...

 

As hombrewers we can fill our cronies and push out with CO2.

The pros have to conserve water as much as possible. They can pessurize the tank and vent repeatedly to get low O2 levels, and even measure those levels. I read somewhere that the trend is to use N2 as it is cheaper.

 

Genius

 

I use an outdoor hose with a whole-house water filter (two hoses with filter in the middle). It fills in a minute or so. Then I add star san. This method is actually faster because you can purge the keg of water very rapidly by turning up the CO2 pressure until the water is almost gone. If you purge the keg without water at the same rate it won't be purged and you will simply waste CO2 which is expensive for homebrewers.

Edit: I hook up the filter because it allows the star san to remain stable and I can reuse it. If I don't use filtered water, the star san quickly becomes milky and viscous.

 

flood and push is an effective method but I always get irked by the amount of sanitizer that remains in the keg (below the dip tube) which is even more substantial for homebrewers (myself not included) who opt to trim their dip tubes a bit.

 

I think about that too, but I typically get out enough to be make it nearly imperceptible when I shake the keg.

A couple ideas:

1. Maybe you can get some more out through the pressure relief valve (turning keg upside-down). I know that valve isn't flush with the lids. It won't get it all.

2. Pump a liter or so of boiled water into the keg after its purged. Then pump it back out using CO2. This will, at least, reduce the concentration of the residual sani solution

 

now that i do this, it's one reason I'm glad i never snipped the bottom of the dip tubes. For me, I was actually surprised how little was left...

 

If you are meaning compressed CO2 expanding and giving cooling, the effect would be very small. Only the gas that is actually expands (10-30 psi) would give you any adiabatic cooling, small and wouldn't last long. Now if you took off your reg and shot the CO2 tank straight into your keg ! ! !

Filling a keg with CO2 will do little to create a permanent blanket. The gases will quickly mix (diffuse). You can pour a Guinness on top of a Bass and have a beautiful Black & Tan because they are liquids . . . but gases have different rules. Same as our atmosphere, the heavy and light gases mix very thoroughly.

The diffusion concept is regularly used in mixing diving gases. Sometimes extra oxygen is added to a cylinder (Nitrox), then air is added on top. The heavier oxygen will mix completely throughout the cylinder. To make Trimix, helium is added to a tank of air (or Nitrox). The very light helium will "sink" (diffuse) to the bottom fairly quickly.

As WickedSluggy says, you can never completely get rid of oxygen by burbing a keg with CO2 . . . but you can get pretty close. If you have an unpressurized keg then air will be at one atmosphere (14.7 psia, or call it 15). If you purge at 15 psi you now have two atmospheres of pressure, half air and half carbon dioxide. Rate of diffusion is based on temp and density, but they will mix fairly rapidly. Venting releases half the pressure (2 ATAs down to 1 ATA) which cuts your air to 1/2. Burp it again at 15 psi and air remaining is 1/4 . . . the third burp will give you 1/8. If you were to increase the burp pressure to 30 psi the air fractions for three burps become 1/6, 1/18, 1/54. This is the percentage of original air remaining, of which 21% is oxygen. A single flood with water and purge will get you there more efficiently if you're talking about purging an entire keg.

For racking, I wait until the keg is full and purge the headspace which is very low volume (roughly one or two inches). It only takes 5-6 minutes to rack, so that is the only real exposure your beer has to air (oxygen). I don't feel this causes any measurable problems and takes minimal CO2. When bottle conditioning the headspace in the bottle (inch or so) is pure air and remains in contact with the beer until the conditioning is complete. This headspace air is never eliminated, just diluted with carbon dioxide. Does anyone every bring up oxidation problems from bottle conditioning? I can't tell the difference from my bottled-carb'ed beer to my kegged beers.

Same here . . . never circumcised my dip tubes and only a couple of tablespoons of liquid is all that's left.

 

Very insightful. If I'm reading this correctly you don't purge your keg at all until full?

 

I was coming to this thread to ask about how you guys purging by pushing liquid sanitizer handled an in keg dry hop. For me, dry hopped beers seem like the best case for going through all the trouble due to the much more volatile nature of what dry hopping brings to the party. The problem is that there is no O2 free way to add dry hops to the kegs. Are some of you torpedoing or using a hop rocket exclusively in place of dry hopping or are you still opening up the keg at some point to add hops?

 

Correct. Actually it's stored with a gallon of sanitizer which is pushed out by CO2. So this mini flood-purge will reduce air by about half. Then after racking, a series of burps gets you close to zero air and IMO close enough. Even complete flooding and pushing leaves the headspace air behind, but it is so small and diluted it can be tolerated (opinion again).

I agree, and accept a smidgen of air entering the keg when adding dry hops. But exposure is short (minute or two) and with a series of burbs the air is minimized quickly. Same with adding finings; work quick and re-burp. Using a torpedo as shown above above eliminates all the air, but this isn't the same as extended dry hopping.

Other techniques?

 

I find that the traditional/easy/lazy way of purging kegs works plenty well without "pushing Starsan". I have enough kegs in my pipeline to really gauge this (at least anecdotally)... 4 and 5 month old IPAs with no signs of oxidation.

What I have also discovered (anecdotally) is that if you happen to forget the Starsan all together and just transfer to a cleanly rinsed of Oxiclean (but unsanitized keg), you will probably be alright. I did this when dryhopping a Pale Ale in kegs that were already full of beer. The first keg is drinking extraordinarily well...but not to push my luck, the second one will probably get consumed quickly.

 

I agree in a clean keg at fridge temps & in the presence of alcohol the risk of infection is probably small. I think most people go the whole 9 yards so make that risk even smaller. I have no problem racking into a freshly emptied keg and have done so w/out issue.

 

I'm pretty surprised some ingenious homebrewer hasn't created a mini hop cannon to blast hops into the fermenter via CO2...hmm, after my fermentation chamber build, i think that maybe my next project

 

it's not really the oxidation of the beer that we're worried about...it's the oxidation of the hop oils. In talking with John Kimmich at the Alchemist, he has measured as low as 1 ppb, but usually get 2-5 ppb DO in his brite tank. It's a major reason that he can maintain such a powerful hop aroma with less than 4oz dry hops/5 gal for Heady Topper.

 

Exactly. I think we are concerned here about LOSS of the compounds that are most vulnerable to oxidation not the DEVELOPMENT of compounds that make beer taste characteristically oxidized.

 

For what it is worth...the only oxidized hops I've tasted were oxidized right out the gate (package). Hard to believe hops will oxidize IN a beer without oxidizing the beer itself. Low beta acid hops are much less suseptible.

4oz is standard for me in a 5 gal IPA batch...with plenty of aroma....just say'in