Author Topic: How much volumes of CO2 per gravity point?  (Read 3680 times)

Offline richardt

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How much volumes of CO2 per gravity point?
« on: May 07, 2010, 07:46:03 AM »
Is there a simple rule of thumb for the level of carbonation achieved if one ferments for awhile in primary and then transfers (before FG is reached) to the keg or the bottle?

For example, given a beer with an OG of 1.070 and assuming a FG of 1.010 as our goal (perhaps even determined by FFT), how many volumes of CO2 could one expect if I filled a 12 ounce bottle with:
1.015 SG beer
1.020 SG beer
1.025 SG beer
1.030 SG beer
1.035 SG beer
1.040 SG beer

How about a 5 gallon Corny keg?

Is there a simple rule of thumb for remaining SG points to be fermented and levels of CO2 produced?
Does some allowance need to be made for pre-existing CO2 levels in beer that is being racked/bottled from the fermenter?

Online tygo

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Re: How much volumes of CO2 per gravity point?
« Reply #1 on: May 07, 2010, 08:17:29 AM »
Clint
Wort Hogs

Fermenting: Wit
On Tap: Lucifer's Hammer Golden Strong Ale, Dopplebock, Old Fuzzynut's Ale

Offline richardt

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Re: How much volumes of CO2 per gravity point?
« Reply #2 on: May 07, 2010, 09:01:20 AM »
Thanks for the links, but Kai might as well be writing in wingdings. ???
It's too complex for me.
I'm looking for a "simple rule of thumb" that doesn't require a calculator (e.g., one "brix" = 4 "gravity points")

Offline a10t2

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Re: How much volumes of CO2 per gravity point?
« Reply #3 on: May 07, 2010, 05:37:26 PM »
The calculations look pretty straightforward. He's saying you'll add 0.5% CO2 for every degree Plato of additional attenuation. Since 0.5% CO2 is about 2.5 vol, you need 0.4°P of attenuation (about 1.6 points) for every volume of CO2 you want to add.
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Offline a10t2

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Re: How much volumes of CO2 per gravity point?
« Reply #4 on: May 07, 2010, 08:52:03 PM »
Thanks for the translation.  I didn't see where 0.5% CO2 equals 2.5 volumes.

I don't think Kai converted, but 0.5 wt% is ~5 g/L, and CO2 density is ~2 g/L.

So, if I bottled a 1.015 SG beer (with no additional sugar) and FG w/in the bottle ended up being 1.010, then my bottled beer should be carbonated to 3 volumes of CO2.

Plus whatever's in the beer to start with. 0.9 vol at room temperature, give or take.
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Offline richardt

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Re: How much volumes of CO2 per gravity point?
« Reply #5 on: May 09, 2010, 05:04:35 PM »
Anthropogenic CO2 comes from fossil fuel combustion, changes in land use forest clearing, and cement manufacture. Houghton and Hackler have estimated land-use changes from 1850-2000, so it is convenient to use 1850 as our starting point for the following discussion.

With all due respect to Malamallotary5 and Rofikss69, this question isn't about atmospheric CO2. 
The environmental debate belongs somewhere else.

I just want a simple "rule of thumb" for gravity points with regards to how many volumes of CO2 get produced for each gravity point. 
Another way of asking the question would be:  "how many gravity points does it take to produce one volume of CO2?"

Online Kaiser

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Re: How much volumes of CO2 per gravity point?
« Reply #6 on: May 09, 2010, 08:32:04 PM »
I'll have to read through my article and check that I got this right. But if you try to calculate the carbonation you can get from residual fermantables in the beer you need to work with the read extract and not the apparent extract. It just so happens that:

delta real extract = 0.82 * delta apparent extract

For each % or Plato of real extract you get 0.5% w/w CO2 since we assume that 1 g of sugar ferments to 0.5 g of CO2 and 0.5 g of ethanol.

With that and some more conversions I get the following rule of thumb:

each gravity point gives you about 0.5 volumes of CO2 and each degree Plato gives you about 4 g/l CO2.

This goes along with the ovservation that priming adds about 3 points, which equals 1.5 volumes CO2 and the remaining 1 volume is assumed to be already in the beer.

Kai
« Last Edit: May 10, 2010, 04:23:50 AM by Kaiser »

Offline a10t2

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Re: How much volumes of CO2 per gravity point?
« Reply #7 on: May 09, 2010, 09:28:47 PM »
With all due respect to Malamallotary5 and Rofikss69, this question isn't about atmospheric CO2. 
The environmental debate belongs somewhere else.

Relax, man. They're just spambots.
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Re: How much volumes of CO2 per gravity point?
« Reply #8 on: May 10, 2010, 06:51:47 AM »
I also updated the wiki article. After doing the math and rearranging some formulas I found that what I had written there was more complicated than it has to be. I liked the “windings” reference, BTW. Though I’m trying to get better at communicating a difficult subject.

It was surprising to me that the OG does not matter even though we need to convert apparent extract (i.e. gravity) numbers to real extract numbers. So I also tested this in my carbonation calculator and it is true, you can change the OG and the carbonation doesn’t change.

Kai

Offline richardt

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Re: How much volumes of CO2 per gravity point?
« Reply #9 on: May 10, 2010, 07:54:06 AM »
With all due respect to Malamallotary5 and Rofikss69, this question isn't about atmospheric CO2. 
The environmental debate belongs somewhere else.

Relax, man. They're just spambots.

Thanks for the education--Had to look that word up--I didn't know what a spambot was, other than annoying.