Why does Temp affect vols CO2?

I can't figure this out. Why do I need more priming sugar, sometimes 50% more, to properly achieve the correct volume of CO2 at 70F than 50F? There is also an impact on kegging temperatures as well, but I don't do that so I am more intrigued by the effects on bottling. Initially I would have assumed that less priming sugar would be needed for higher bottle priming temperatures as there would be stronger yeast activity to get to the target volumes of CO2. Here is Palmer's nomograph:



Can someone explain?

Ironic, I just mentioned this in another thread: https://www.homebrewtalk.com/f37/need-advice-carbonated-out-secondary-150665/

Gas solubility increases with decreasing temperature. So a beer at room temperature dissolves less C02 than a beer at 35 F. That nomograph accounts for the amount of C02 already dissolved in your beer prior to bottling.

There are web-based calculators that do the same thing.

EDIT: Re-read your post. The temperature axis on the nomograph is the temperature at bottling, NOT the conditioning temperature. You should condition the beer at 70F and then chill to serving temps to achieve the proper carbonation levels. Revvy has a great blog post about this.

Most brewers always assume you are bottle carbing at about 65-70 deg, anything lower is going to take a long time to carbonate due to the yeast going dormant and just being slow. I dont think this post is anything like the other post mentioned.

JesseRC said:

I dont think this post is anything like the other post mentioned.

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It's all about the residual CO2 left in solution from fermentation, so it's exactly the same thing.

Like mentioned above, a beer at a colder temperature will have more C02 dissolved in it because of an increase in solubility with the colder temp. However, an important point to note is that while in the primary or secondary (so long as their is some kind of pressure release), the amount of co2 dissolved in your beer will be in reference to the warmest temperature it has been at (if finished fermenting). For example, if the beer was fermented at 50deg and then lagered at 35, when you bottle it you should calculate the amount of bottling sugar for the 50deg even though the beer might be at 35 at the time of bottling. This is because when you drop the temperature to 35, there is already a fixed amount of CO2 available so even though them temp decreases the CO2 stays the same. Hope that makes sense and helps.

One more note:
The yeast activity should be considered in the amount of time it takes to carbonate the beer, not so much in your final carbonation levels. It does not affect the final amount of C02 that can be dissolved, which is temperature and pressure dependent. While your yeast may be more active at higher temperatures (leading to faster carbonation), they will eventually run out of sugar and consequently can not produce more C02 (less pressure) to carbonate your beer.

I hope that makes sense. Sorry for the multi post.

Rushis said:

Gas solubility increases with decreasing temperature. So a beer at room temperature dissolves less C02 than a beer at 35 F. That nomograph accounts for the amount of C02 already dissolved in your beer prior to bottling.

There are web-based calculators that do the same thing.

EDIT: Re-read your post. The temperature axis on the nomograph is the temperature at bottling, NOT the conditioning temperature. You should condition the beer at 70F and then chill to serving temps to achieve the proper carbonation levels. Revvy has a great blog post about this.

Click to expand...

So let me get this straight... If I leave my bottles at 70F to fully condition, I will need more sugar to make up for the CO2 that doesn't get dissolved in the beer. I'm guessing it just hangs out in the neck space of the bottle?

Also, if I conditioned my bottles at 70F, which accounts for more sugar, and they fully conditioned at that temperature, then I moved them for a month or so to 50F, the previously undissolved CO2 would then end up increasing the volumes of CO2 in the beer. Is that correct? Wouldn't this also be the case if bottles were fully conditioned and later moved to a refrigerator for a few months?

What I am gathering after all of this is that it's best to leave the bottles at a consistent temperature for the entire lifespan of the beer until right before consumption to ensure desired volumes of CO2. If you are going to store beer for a long period of time at 50F, after a three week conditioning at 70F, then you should prime for 50F because that is the temperature where the CO2 will be absorbed to its highest degree.

Am I making sense? I think I'm just rambling now...

jmo88, you're missing the point completely. This has nothing to do with bottle conditioning temps at all, it's the temperature of the beer at bottling, which will determine how much CO2 is already in it.

yeqmaster said:

Like mentioned above, a beer at a colder temperature will have more C02 dissolved in it because of an increase in solubility with the colder temp. However, an important point to note is that while in the primary or secondary (so long as their is some kind of pressure release), the amount of co2 dissolved in your beer will be in reference to the warmest temperature it has been at (if finished fermenting). For example, if the beer was fermented at 50deg and then lagered at 35, when you bottle it you should calculate the amount of bottling sugar for the 50deg even though the beer might be at 35 at the time of bottling. This is because when you drop the temperature to 35, there is already a fixed amount of CO2 available so even though them temp decreases the CO2 stays the same. Hope that makes sense and helps.

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I think you just answered my underlying question. I am just not sure why just yet. The bold part above confuses me. I thought more CO2 is produced with more sugar and more is absorbed with a lower temp. So this change in temp without the beer absorbing the CO2 is still confusing.

Scimmia said:

jmo88, you're missing the point completely. This has nothing to do with bottle conditioning temps at all, it's the temperature of the beer at bottling, which will determine how much CO2 is already in it.

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I think you and I are using different words for the same thing. Perhaps I am using the term conditioning incorrectly. When I put the cap on, everything after that point I meant as conditioning.

And that's the problem. After the cap goes on, it doesn't matter one bit. This has everything to do with temps BEFORE bottling, not after.

Scimmia said:

And that's the problem. After the cap goes on, it doesn't matter one bit. This has everything to do with temps BEFORE bottling, not after.

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Ding ding ding!

Once you cap the bottle, your yeast will eventually create a fixed quantity of C02. The total amount of C02 present in your bottles is determined by 1) the residual C02 dissolved in your beer after fermentation and 2) the amount of sugar you added that the yeast will convert into C02.

How much of that C02 dissolves into your beer will determined by the serving temperature. If your beer is too warm, most of the C02 will be headspace of each bottle, not in solution, resulting in a flat beer.

Condition your beer at 70F so the yeast can convert all of the sugar into C02 (2-3 weeks). And the chill your beer to get the C02 to dissolve into solution (1-2 days at serving temperature).

Does that help?

Scimmia said:

And that's the problem. After the cap goes on, it doesn't matter one bit. This has everything to do with temps BEFORE bottling, not after.

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Okay. Bare with me here. I don't understand why this is. To give an example of what I think you all are saying: A lager that finishes fermentation at 50F absorbs more CO2 and should be primed for 50F even though it sits in the bottle and ferments a little more to produce more CO2 at 70F.

Don't get too frustrated with me now, I can be a slow pony sometimes. But at least I understand more than I did twenty minutes ago.

A fixed amount of sugar added will create the same amount of CO2 in volumes no matter what temperature it sits at while carbing (assuming its warm enough for the yeast to actually do their job). However, once chilled, the temperature of the beer determines how many of those volumes will actually get absorbed into the beer. The colder the beer, the more easily gaseous CO2 in the headspace will be absorbed into the liquid.

At least, that's how I understand it.

Edit: Rushis beat me to it.

jmo88 said:

A lager that finishes fermentation at 50F absorbs more CO2 and should be primed for 50F
YES, assuming you are bottling the beer at 50F. Your bottling bucket or fermentor is an open system, as the beer warms up from 50F C02 to leave the solution and float away into the air. Once this C02 leaves it can not go back into solution.

even though it sits in the bottle and ferments a little more to produce more CO2 at 70F.

Once the bottle is capped, it is a closed system. No CO2 can escape from the closed environment. As the yeast makes more C02 it is trapped in the bottle. The temperature that you serve your beer will determine how much of that trapped C02 is used to carbonate your beer.

Don't get too frustrated with me now, I can be a slow pony sometimes. But at least I understand more than I did twenty minutes ago.

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Gas solubility confused the heck out of me in my thermodynamics class in college. It's not an intuitive process.

Okay. I finish all my ferments between 65-68. Just prime according to style at that temp regardless of what temp the bottle sits at. Though I don't fully understand why –yet– I can see that this is the right way to go about it.

:rockin::rockin:

jmo88 said:

Okay. I finish all my ferments between 65-68. Just prime according to style at that temp regardless of what temp the bottle sits at. Though I don't fully understand why –yet– I can see that this is the right way to go about it.

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You've got the procedure down.

It may be useful to read up on how force carbonation in a kegging system works. Conceptually, it is easier to understand because you've taken the yeast activity and priming sugar out of the equation. Think of the "yeast/priming sugar" as a miniature CO2 tank for each bottle.

There are a few different ways CO2 gets into beer. Take an ale ferment at 70f. As it ferments with an airlock, the pressure of the CO2 in the vessel is equal to atmospheric, if not a slight bit higher, or about 15psi. However, if you look at the chart, 15psi at 70F isn't worth much in carbonation. Take that same beer fermented at 50F. Look at the chart for 15psi and 50F.

Here's a weird mental exercise. Take a bottle of distilled water and test the pH. It's 7. Leave the cap off and notice a drop in pH over time. That's atmospheric CO2 dissolving into the water creating carbonic acid. Why? The partial pressure on the headspace is atmospheric all around you.

When you bottle, you're generating partial pressure of CO2 way in excess of atmospheric. More like 40psi at room temp. It eventually dissolves into the beer over the 3 week conditioning period. It always helps to chill the beer down so that co2 is more likely to stay in solution when it's opened and poured.

You can also get a greater appreciation for this 'gas solubility and temperature's affect' by making wine at home.

Wine has to be degassed to get rid of the CO2 that's already in solution (assuming you're not making a sparkling fruit wine or something). This time of year, basement wines are a little too cool for good degassing. Short of using a vacuum to pull the CO2 out, you have to raise the temperature up into the 70's to really degas proper.

But in the summertime its a lot easier to degas because the finished wine is usually 70F already, not 60F or colder.

jmo88 said:

Okay. Bare with me here. I don't understand why this is. To give an example of what I think you all are saying: A lager that finishes fermentation at 50F absorbs more CO2 and should be primed for 50F even though it sits in the bottle and ferments a little more to produce more CO2 at 70F.

Don't get too frustrated with me now, I can be a slow pony sometimes. But at least I understand more than I did twenty minutes ago.

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I guess there is one thing we really haven't said yet, hopefully it will make a difference.

During fermentation, the yeast is creating CO2, and that CO2 is dissolved in the beer. As more and more CO2 is produced, it begins to come out of solution, which is the bubling in the airlock. Not all of it comes out of solution, though, some stays. The amount that stays depends on the temperature of the beer, the colder it is, the more CO2 it can hold before it comes out of suspension. Since there's already more CO2 in solution, you need less sugar. Starting to make sense?

Scimmia said:

I guess there is one thing we really haven't said yet, hopefully it will make a difference.

During fermentation, the yeast is creating CO2, and that CO2 is dissolved in the beer. As more and more CO2 is produced, it begins to come out of solution, which is the bubling in the airlock. Not all of it comes out of solution, though, some stays. The amount that stays depends on the temperature of the beer, the colder it is, the more CO2 it can hold before it comes out of suspension. Since there's already more CO2 in solution, you need less sugar. Starting to make sense?

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Ah.... (light bulbs). You have given me this remaining piece to the puzzle. Crystal clear:fro::fro::fro::fro:

Bobby_M said:

As it ferments with an airlock, the pressure of the CO2 in the vessel is equal to atmospheric, if not a slight bit higher, or about 15psi. However, if you look at the chart, 15psi at 70F isn't worth much in carbonation. Take that same beer fermented at 50F. Look at the chart for 15psi and 50F.

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Off topic from the thread, but now I'm really confused.

According to the charts, at 15psi (atmospheric pressure) and 50 degrees you will get 2.3 volumes, and 2.7 volumes at 40 degrees. So, why is a lager that was fermented at 50 degrees and lagered at 40, not already fully carbed? It's been constantly exposed to a pure CO2 at 15psi just as it would be in a keg.

And a dumber question. Atmospheric pressure is about 15psi. So, why if I set my regulator at 10psi does CO2 come out? Seems like atmospheric pressure being greater would hold it back.

Sorry for the science lesson hi-jack . . .

I spaced out and forgot that the chart pressure and what you see on your regulator is pressure in excess of ambient.

Although it doesn't show it, you can figure out what it would be at 0psi on the chart and that would be your volumes at atmospheric CO2 levels. Take the 50F row that you mentioned. 2.3 volumes at 15 psi. It's not exact but you lose .1 volumes for every one less psi. So you'd have about 1 volumes at 0 psi.

You can use this calc too... http://www.brewheads.com/forcecarb.php
Set the temp, then trial and error the volumes until you see 0 psi.

At 35F, atmospheric gives you 1.5 volumes.
At 70F, atmospheric gives you .7 volumes.