Carbonation tab -- possible bug

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Carbonation tab -- possible bug

Postby billvelek » Fri Aug 28, 2009 9:39 am

I don't know if this is a bug or not, because I might not understand carbonation well enough, but here is my question: using "Natural Conditioning", when the "Beer Temperature" is changed, why does either the "Priming Agent Mass" or the ''Volumes CO2" change (one or the other depending on whether the lock is checked)? I might be wrong, but it seems to me that the "Volumes CO2" should be absolutely fixed based upon the "Priming Agent Mass", regardless of temperature, and that the 'pressure' (which is not shown) is what actually changes. In other words, it seems to me that a certain amount of primer contains a certain number of molecules of sugar from which a certain amount of CO2 is produced by fermentation; the certain amount of CO2 establishes a certain 'volume' of CO2. If I am incorrect, then I will greatly appreciate an explanation. Thanks.

Cheers.

Bill Velek
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CO2 volumes and temperature

Postby slothrob » Sun Aug 30, 2009 6:50 am

This is because the beer has a certain amount of CO2 already dissolved in it, dependent on its temperature. The lower the beer's temperature the more CO2 is dissolved in it, so less priming sugar is required to hit the same volumes of CO2.
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Thanks, Slothrob ... what about this?

Postby billvelek » Sun Aug 30, 2009 10:46 am

Thanks, Slothrob; that makes perfect sense and I should have figured that out myself. At the time that I had posted, I was engaged in a completely different discussion in another forum -- about "pressure" changes with termperature, and the effect of refrigerating over-carbonated beers that were causing bottle bombs in order to lower pressure -- and I had used BTP to recommend the priming rate for a certain volume of CO2 in the future, so I just already had pressure versus temperature on my mind, and posting after a few beers doesn't help either.

But now that we're discussing the BTP carbonation tab and the effects of temperature on dissolved CO2, I am curious about some other possible factors. I realize that carbonation levels are probably the least important of all beer characteristics and I'm probably getting 'anal', but BTP is so extremely scientifically precise in every other regard that I'm curious about a few things and whether they are likely to have a significant enough of an impact that they ought to be taken into consideration by BTP if there is any practical way to do so (perhaps the program already does).

First, is there normally a loss of dissolved CO2, and if so, how much is typically lost (enough to be significant?), when beer is raked into a secondary after all fermentation has finished in the primary?

Second, does the amount of time that beer sits in a fermenter (primary and/or secondary), make any difference? My guess is that it probably doesn't if the fermenter is sealed.

Third, does altitude and barometric pressure make much of a difference? I assume that after all fermentation has finished, that the highest temperature and the lowest pressure combination at any time while the beer has been sitting there will cause the lowest level of CO2 saturation, and that there is no way for it to recover that CO2.

Fourth, the amount of 'water' added along with the primer does not contain any dissolved CO2, but there does not appear to be any way to adjust for that; I suppose that this is a very minor factor which shouldn't normally make more than as much as a 5% difference, but there have been times when I've added distilled water to lower my gravity and bitterness at bottling time.

Cheers.

Bill Velek
Visit www.tinyurl.com/bvelek - portal to my brewing sites: 3,100+ members on 'Grow-Hops', and 1,350+ brewers on my 'BrewingEquip' group.
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CO2

Postby slothrob » Tue Sep 01, 2009 5:43 am

Hi Bill,

1) I don't know if the amount of CO2 that gets knocked out can be controlled for. It seems like it would depend on each person's technique. This is probably where one person might choose to add a bit more sugar, based on experience with their own system.

2) I don't think the time will matter, once the CO2 dissolved has had a chance to equalize to temperature.

3) Pressure would seem to affect CO2.I don't know how much and I doubt this is controlled in BTP. Temperature variation will matter, but it takes some time for the CO2 change to equalize, so short changes shouldn't matter much. I've wondered about what happens when the temperature drops again... wouldn't the CO2 rich head space be a source of CO2 to re-dissolve in the beer?

4) If you add a large amount of boiled water, perhaps you would want to use the priming calculator to estimate the difference this might cause in the dissolved CO2 level, just to be safe. I suspect, as you do, that it is usually so little water as to make an imperceptible difference.
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