View Full Version : Filling/layering with CO2?

04-18-2013, 03:55 PM
I read several things in the newbee guide about filling bottles with CO2, or layering a fermenting mead batch with CO2 on top? But I couldn't really find anything that explained A) why this was done, or B) how this was done. Are there tools for putting CO2 into an empty bottle? A trick to it? What is the deal with CO2 and mead bottling?

04-18-2013, 05:31 PM
I don't think layering with CO2 does much for bottling, but it can be helpful during fermentation. The CO2 is heavier than regular O2, so it "displaces" the oxygen in a carboy to protect the mead from oxidation which would ruin a batch quickly. If you van find it, I've seen people using Argon gas which is heavier than CO2. I think its weight would allow it to better "blanket" the top of the mead.

I've seen small canisters of Argon gas (about a 1/3 of the size of a cooking spray can) at my LHBS, but I've never tried it. Conversely, you can just ensure your carboys are topped-up to reduce the head space in your carboy to allow less room for oxygen.

Hope that helps! : )

Medsen Fey
04-18-2013, 09:24 PM
There is no layering to speak of - the gas will diffuse throughout the space. You use the gas, whether heavier or lighter than air, to displace and flush out all the oxygen in the space. That protects wine/mead against oxidation. Most meads are relatively resistant to oxidation and you may not need this.

04-18-2013, 09:36 PM
The "layer" of gas is misleading at best, and frankly I'd call it total BS. [It is, however, a commonly cited technique and is used to sell you stuff.] All these gases (regular air, CO2, Ar, N2) are roughly the same mass. You don't get concentration gradients due to weight unless you are talking about thousands of feet, and even at the top of Everest there is still some oxygen in the air. Argon is actually a bit lighter than CO2, although it's heavier than O2. But again, these are really small differences. Gravity is a very, very weak force when acting on small masses, and for our purposes entropy always wins this particular battle. Entropy says the gases should be mixed, and thus they are.

You can reduce the amount of oxygen in a container by flushing out the volume with another gas. Notice "reduce", not "eliminate". You'll want to flush the space with at least 3 times its volume with your inert gas, be it CO2, N2 or Ar. The more you flush, the less oxygen will be in the container. But, the longer it sits there after you turn the gas off, the more oxygen will creep back in.

You can get a valve with a long tube attached. Hook things up to a gas cylinder. Stick the tube in the bottle, open the valve, shoot gas into the bottle. Close the gas valve, fill the bottle. This way you'll have less oxygen exposure, which will help the mead last longer. You can also flush out your carboys (or kegs!) for the same reason.