[ipaguy]

I've heard 'authorities' say something along the lines that when bottle conditioning beer, the CO2 is initially all (or mostly) in the head-space, and takes a week of two to dissolve into the beer.  I was immediately skeptical, so I did some caclulatin':  Assume that you're going for 2 volumes CO2 carbonation level, and have about 15 ml of head-space in the bottle.  For all of the CO2 to be up in the head-space after priming sugar ferments, I figure that the pressure in the bottle would be around 710 psi!!!  I think not.

[tumarkin]

yeah, well, you know what they say about 'authorities.'  the additional CO2 is going to be produced gradually as the yeast does it's thing. even if the CO2 all rises into the head space as it's produced, it's going to constantly be seeking equilibrium & balance between the headspace & beer.

[euge]

I think I brought this up a few days ago. I believe it's total BS about ALL the gas being in the headspace. http://www.homebrewersassociation.org/forum/index.php?topic=4332.0

The beer will have most of the co2 dissolved into it as it's farted out by the yeast. There is an excess so it also fills the head-space. Simply put it reaches an equilibrium since it cannot escape the bottle. When the temp changes to the cooler it allows a bit more from the gas-space to re-enter the solution. If heated more will come out and if heated enough the bottle will burst. Think piston.

This is a non scientific explanation. Others could reveal more technical info far better than I can.

A ridiculous old homebrewer's tale. That's what it is lol...

[ipaguy]

I'd be happy to show my calc's if anyone doesn't believe me, but I personally wouldn't want to be anywhere in the neighborhood of a bottle pressurized to over 700 psi. 

[tschmidlin]

I'd be happy to show my calc's if anyone doesn't believe me, but I personally wouldn't want to be anywhere in the neighborhood of a bottle pressurized to over 700 psi. 

I don't know the psi rating for a glass bottle, but cornies are only rated for 120psi.  I'm guessing a bottle is much lower than that 

[narvin]

I have not heard this, but I have heard that bottles with insufficient head space do not carbonate as well.  This could actually be plausible, due to the fact that a gas buffer is more compressible and will allow CO2 to be released from fermentation without increasing pressure on the yeast, and gradually equalize between the liquid and the gas.  This is still just speculation, though.

[tschmidlin]

I have not heard this, but I have heard that bottles with insufficient head space do not carbonate as well.  This could actually be plausible, due to the fact that a gas buffer is more compressible and will allow CO2 to be released from fermentation without increasing pressure on the yeast, and gradually equalize between the liquid and the gas.  This is still just speculation, though.

No, I think you have the theory right.  Especially at bottle conditioning temps, CO2 will be less soluble in the beer so having somewhere it can go to build up pressure should be helpful.

If anyone who bottle conditions is willing to do this, I'd love to hear what happens - bottle as normal, but leave one uncapped and and just put a balloon on top.  Wrap a rubber band tightly around the neck to hold the balloon in place, then leave them to carbonate.  Measure the diameter of the balloon over time as the bottles condition.  Then when they are done carbonating, put them in the fridge and check the diameter of the balloon while the beer chills and see what it is at various temperatures.  I think that would be cool.   

[ipaguy]

Another experiment to try would be to fit a swing top cap with an automotive type valve, and take pressure readings every couple hours.  You could compare results w/ different amounts of headspace.  I'd be willing to bet that with normal headspace the pressure never gets above around 20 psig.  My original point is that the 'most of the CO2 in the headspace' myth is ridiculous on the face of it, so I have no fear of 700 psi bottles.  Looking through my brewing library, I see that Dave Miller's Homebrewing Guide perpetuates this craziness.  This is disappointing coming from someone I otherwise consider one of my favorite authors.

[kerneldustjacket]

I agree with euge...you just can't have all the CO2 in the head space at once.
Some of it must be going into saturation while it's being produced.
Heck...I'll bet you could put an un-capped, just-primed bottle of beer in a 48 F fridge, and have it come out several days later with more CO2 in solution than when it went in!

Consider cask-conditioned ales: the casks are not "airtight;" they allow excess CO2 to escape (Yes...even when a hard spile is in place...it's just a slower release, so more CO2 is forced to "stay around" and go into the beer)
Anyway, the volume of CO2 held by the ale is related to the ambient temperature in which the cask is being stored -- colder storage, more carbonation. (but too cold and the yeast ferments too slowly to produce enough CO2 to keep up with "losses")

I had to learn most of this after trying to use a 5.4 gallon stainless steel pin I bought 4 years ago. I put a just finished English Mild into the pin, primed it, put the shive and keystone in place, drove in a hard spile, and then left the beer to "carbonate." The next day I noticed "foaming and bubbling" from around the shive. "What? thought I, "Why is this not airtight?"
Through research -- and very basic at that -- I discovered that I had to store the cask in the high 40s if I expected to retain enough CO2 to hit 1.5 volumes of CO2...or thereabouts. Room temperature just won't do it...the CO2 "leaves" the beer instead of saturating it.

Oh...and even though it was only *slightly* carbonated, the mild was tasty. 

[malzig]

I've heard 'authorities' say something along the lines that when bottle conditioning beer, the CO2 is initially all (or mostly) in the head-space, and takes a week of two to dissolve into the beer.

I've never heard that before.  However, it certainly takes a week or two, at best to build up enough CO2 to fully carbonate the beer, but CO2 is going into solution gradually over time.  The other thing is that, after a couple weeks, all the CO2 might have been made, but since the beer is warm a great deal of the CO2 remains in the headspace and the carbonation in the beer will be lower than it will be after a couple days in the fridge.  This is just like the case where a keg will be undercarbonated at room temperature if held at the same pressure that would fully carbonate it at fridge temperatures.

[ipaguy]

I've heard 'authorities' say something along the lines that when bottle conditioning beer, the CO2 is initially all (or mostly) in the head-space, and takes a week of two to dissolve into the beer.

I've never heard that before.  However, it certainly takes a week or two, at best to build up enough CO2 to fully carbonate the beer, but CO2 is going into solution gradually over time.  The other thing is that, after a couple weeks, all the CO2 might have been made, but since the beer is warm a great deal of the CO2 remains in the headspace and the carbonation in the beer will be lower than it will be after a couple days in the fridge.  This is just like the case where a keg will be undercarbonated at room temperature if held at the same pressure that would fully carbonate it at fridge temperatures.

The example of the keg is quite different than a bottle.  In the keg, you're talking about gas at constant pressure, and you're exactly right about the undercarbonation.  With the bottle, you're talking about a constant volume of CO2, where the pressure in the bottle will increase with temperature.

I won't argue that beer can take time to condition.  I usually only keep my bottles at room temp for a day after bottling, and then more them to my 60 - 65F crawlspace.  I've had big beers take as long as 2 weeks to fully carbonate.

The thing that burns my biscuits is the myth that 'most' of the CO2  is in the headspace after all of the priming sugar has fermented.  This would absolutely require that the pressure in the bottle would have to be somewhere in the 300 - 700 psi range.  That's just basic physical chemistry.  That's also clearly ridiculous on the face of it.  Also, when have you seen CO2 bubbles rising in a bottle of conditioning beer?  Those little yeast cell are excreting CO2 into the liquid only a few molecules at a time.  That's a lot more efficient at establishing equilibrium than even your best diffusion stone.  Sorry for the rant, but I feel the need to call out B.S. when I see it.

[malzig]

The thing that burns my biscuits is the myth that 'most' of the CO2  is in the headspace after all of the priming sugar has fermented.

But where have you ever seen this said?  Your post was the first time I'd ever heard anyone mention a claim that most of the CO₂ was in the headspace.  I'm pretty sure a significant amount of the CO₂ is in the headspace of a warm beer, though.

The example of the keg is quite different than a bottle.  In the keg, you're talking about gas at constant pressure, and you're exactly right about the undercarbonation.  With the bottle, you're talking about a constant volume of CO2, where the pressure in the bottle will increase with temperature.

Temperature is why the carbonation is lower in a warm bottle of beer, since the pressure at temperature and the solubility at temperature curves don't mirror each other.

If you take as an example a beer that you want to serve at 2.5 volumes of CO₂ at 40ºF, the final pressure in the bottle will have to be about 12.3 psi at 40ºF.  Then, if you solve PV = mRT for constant volume and mass, you find that the pressure would increase about 1.06-fold for a rise in temperature from 40ºF to 70ºF:
1xRx294ºK / 1xRx278ºK = 1.06
12.3 psi (at 40ºF) x 1.06 = 13.0 psi. (at 70ºF)

However, the solubility of CO2 decreases at warmer temperatures.  If the bottle is at 13.5 psi and 70ºF, then the beer will have 1.52 volumes of CO₂, instead of the 2.5 volumes it would have had at 12.3 psi and 40ºF, despite the slightly higher temperature.

So, most of the CO₂ isn't in the headspace in a warm beer, but 39% of the CO₂ that you want in the beer is still in the headspace.  That's going to take some amount of time to get into the beer when you chill it, just as it would if you had a keg at 1.52 volumes and you increased the pressure to get it to 2.5 volumes.

Edit: Fixed some sloppy math.  I'm pretty sure the logic is sound, but I'm not much of a physicist, so I could be missing something that makes the actual values wrong.

[ipaguy]

I know I'm beating this to death, but for clarity let me state the myth as I understand it (and then proceed  to debunk):  As I read Dave Miller's book, I understand him to say that after condition of bottled beer is completed at room temperature 'most' of the CO2 is in the headspace of the bottle.  This is the statement I want to challenge, so whatever happens after moving the beer to a lower temp for aging/lagering is beside the point.

I took some measurements to be able to duplicate what is the most likely bottling scenario:  Priming 5 gal of beer with 3/4 cups corn sugar, and bottling into standard 12 oz long necks with a Fermtech bottle filler.  Measurements taken were:

3/4 cups corn sugar = 107 g
beer volume = 359 ml
headspace volume = 16 ml

Calculations were as follows

total glucose used = 107g / 180g/mol =  0.594mol
total CO2 produced = 0.594mol x 2 = 1.188mol

total CO2 produce (by gas law) = (1.188 mol) x (0.0821 L atm / mol K) x (295 K) = 28.8 L atm

total volume of beer = 5 gal = 18.93 L

CO2 produce per volume of beer = 28.8 L atm / 18.93 L = 1.52 L atm / L = 1.52 ml atm / ml

total CO2 per bottle = (1.52 ml atm / ml) x 359 ml = 546 ml atm

1/2 of the total CO2 = 273 ml atm

pressure in headspace if 50% of CO2 is there = 273 ml atm / 16 ml = 17.1 atm = 256 psi

I like this way of calculating things because it doesn't depend on knowing anything about what's happening in the liquid phase or how beer carbonation levels are defined.  I don't use anything but actual measurements an application of the gas law.

[swihart]

If anyone who bottle conditions is willing to do this, I'd love to hear what happens - bottle as normal, but leave one uncapped and and just put a balloon on top.  Wrap a rubber band tightly around the neck to hold the balloon in place, then leave them to carbonate.  Measure the diameter of the balloon over time as the bottles condition.  Then when they are done carbonating, put them in the fridge and check the diameter of the balloon while the beer chills and see what it is at various temperatures.  I think that would be cool.   

This is a totally cool idea but remember that balloons are not very gas tight.  Even filled with air, they deflate over days.  Helium leaks out fastest because it's such a teeny little atom, and CO2 would leak out more slowly.  But some would leak out.  But the experiment would still be cool to see/do.

[tschmidlin]

If anyone who bottle conditions is willing to do this, I'd love to hear what happens - bottle as normal, but leave one uncapped and and just put a balloon on top.  Wrap a rubber band tightly around the neck to hold the balloon in place, then leave them to carbonate.  Measure the diameter of the balloon over time as the bottles condition.  Then when they are done carbonating, put them in the fridge and check the diameter of the balloon while the beer chills and see what it is at various temperatures.  I think that would be cool.   

This is a totally cool idea but remember that balloons are not very gas tight.  Even filled with air, they deflate over days.  Helium leaks out fastest because it's such a teeny little atom, and CO2 would leak out more slowly.  But some would leak out.  But the experiment would still be cool to see/do.

Good point - maybe use a mylar balloon instead, that will prevent leakage through the balloon, but then the diameter isn't as easy to measure since it doesn't stretch like a regular balloon.  And it might be harder to get a good seal around the neck, but you could use some glue or something to prevent that.  Hmmm, stretchy balloons that are not gas permeable . . . maybe they exist.