View Full Version : Carbonation/priming question

03-15-2013, 07:45 AM
Just wanted to check I'd understood things correctly...

From what I've read, after fermentation, a brew should contain about 0.85 volumes of CO2, if not degassed. So if I wanted to carbonate to 2.85 volumes, I could either fully degas and add priming sugar for 2.85 volumes, or not degas at all and add sugar for just 2 volumes (plus perhaps a bit more to adjust for CO2 escaping whilst bottling).
Is this correct?

03-15-2013, 12:03 PM
Basically, yes. The amount of residual gas in solution will depend on temperature (higher temp means less residual CO2) and the amount of time it's been sitting there. I've noticed a pretty quick drop from 2 weeks to 4 weeks in the amount of residual CO2 (as measured by how carbonated it is after priming to the "same" level). It's probably more reproducible to degas completely and prime to your desired level, especially if you're letting the mead age at all in the carboy.

Marshmallow Blue
03-15-2013, 12:19 PM
How do you determine the amount of Co2 in your mead? I know you can calculate what your adding by the amount of sugar but what about whats in your must /mead?

03-15-2013, 01:45 PM
I like to use this handy widget (http://hbd.org/cgi-bin/recipator/brew/widgets/bp.html).

03-15-2013, 02:41 PM
So you can normally rely on a mead being completely degassed due to the long aging process? In this case I'm actually carbonating a couple of hydromels that won't be aged at all, so I think I'll go with the non-degassing method, as it's probably better to end up under-carbed, than accidently over-carbing due to not having got all the CO2 to start with.

Marshmallow, if you're enquiring about that figure of 0.85, that's from using the equation (Henry's Law) with a 100% CO2 environment under 1 atmosphere of pressure at 20C (ie inside an airlocked carboy immediately after fermentation). As for the CO2 at any other time, I don't know if that's possible.

03-15-2013, 04:26 PM
The CO2 remaining in solution is, in theory, an equilibrium condition. So no, I don't think you will get complete removal of CO2 just by waiting (unless you leave the top open, but then you have other problems). Anecdotally, I do think you lose some of the calculated value over time. Could be from just being moved around, small temperature changes, whatever. Maybe I'm crazy. :eek:

Medsen Fey
03-15-2013, 04:41 PM
If you don't let it degas, it is hard to imagine it is clear. You are probably going to wind up with a ton of yeast sediment in the bottles and that may potentially have a negative impact on flavor.

Sent from my DROID RAZR using Tapatalk 2