A few questions about carbonation levels and bottle conditioning.

I am trying to learn a little bit more about carbonation levels for bottle conditioned beer. I tried reading up on the subject, but have a few questions:

1. Assuming gallons are the form of measurement, when a beer has 2.5 volumes of Co2, does this mean for every gallon of beer, 2.5 gallons of Co2 are dissolved in the liquid?

2. From my understanding, Co2 more easily dissolves into liquids at lower temperatures. How does this affect the amount of carbonation in the beer? For instance, if you bottle and condition at 66F and then later keep in the fridge at 35F, is the amount of Co2 in the liquid the same? Likewise, what would happen if the beer is stored at higher temperature? I'm just confused because the online priming calculators use bottling temp, but don't use storage/fridge temp so I am unsure how temps affect these numbers.

3. What is the max PSI a normal, 12 oz. glass beer bottle can hold?

4. Obviously the carbonation levels in the bottle will not change based on temperature since the yeast produce X amount of Co2. What determines how much Co2 is in the liquid and how much is in the headspace?

Thanks for the help!

1. correct - V/V at atmospheric pressure that is
2&4 - you got it again - The yeast produce X amount of Co2 assuming temp for active range of strain used (can be slower or fast per temp range just like primary fermentation. At colder temps the liquid will "hold" more gas at atmospheric pressure (once cap is removed, or while pouring). At warmer temps the gas will become easier to release from solution (uncapping a brew thats been sitting in the sun may look more like a volcano)
3 - no clue, but from mishaps in the past it seems the seal on most caps are the weak link in most cases.

I second question #2 and am looking for a practical application answer. If CO2 diffusion is a function of temperature, pressure and quantity of CO2. By holding one of the three constant, the other two can change in simple relationship. We know this is true from our forced carbonation kegging techniques - we hold the temperature constant and change the pressure to achieve various carbonation levels.

However, when bottle conditioning, the temperature changes - especially for ales. we condition and one temp and store / serve at another because of ale yeast properties. When bottle conditioning, we hold the amount of CO2 available constant by virtue of bottling our beer. Therefore, as the temperature (and ergo pressure) changes, so will our CO2 diffusion. This is why I don't understand why carbonation calculators use conditioning temp and not cold storage / serving temp in the equation. Thats a 30+ degree change in temp and will affect the amount of sugar I use for a 5 gallon batch by almost a full oz (or ~26%). As a math guy, thats way outside the acceptable differential for statistics.

My experience confirms this. Whenever I bottle condition, my beers seem perfectly carbed at room temp and over-carbed once they've been in the fridge for awhile - to the point of fault. My next batch to bottle is a stout and I really, really don't want over carbonated beer so I am thinking about carbing based on cold storage temp. I know it will be flat when its warm, but given a couple of days in the fridge, the pressure inside that bottle should force more CO2 down into the beer, right?

Thoughts?

The amount of CO2 in the bottle is determined by two things - yeast and their food (sugar). As long as the temperature is within a comfort range for the strain of yeast you are using, there will be about the same total amount of CO2 available after the yeast has "finished eating". There of course may be slight difference due attenuation ability at different temps for certain strains, but time to finish will be the biggest difference. The ability of the beer to absorb CO2 is what changes greatly with temperature. At lower temps, the beer will absorb more C02, where at warmer temps the C02 will be trying to "escape" (more will be trapped in the head space).
Generally accepted is to condition at around 70 (allows the majority of beer yeast to work quickly), then chill (allows the C02 developed at warmer temps to be absorbed into the beer).

501irishred said:

3 - no clue, but from mishaps in the past it seems the seal on most caps are the weak link in most cases.

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I also don't know that limit off the top of my head, but I can assure you that the seal on the caps is typically NOT the weak link. Surely you have heard the term "bottle bomb" being tossed around on these forums? This is because very overcarbed bottled (most often due to infection or bottling before fermentation is complete) will explode, sending glass shards everywhere. One rarely reads of caps simply popping off.

homebrewdad said:

I also don't know that limit off the top of my head, but I can assure you that the seal on the caps is typically NOT the weak link. Surely you have heard the term "bottle bomb" being tossed around on these forums? This is because very overcarbed bottled (most often due to infection or bottling before fermentation is complete) will explode, sending glass shards everywhere. One rarely reads of caps simply popping off.

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Guess it varies on the bottles being used (makes question from OP even more interesting). I personally use old Sam Adams bottles and have unfortunately seen mass eruptions on two separate occasions. Once when the thermostat on my beer fridge stuck and super froze all contents (talk about a sick feeling!). Out of over 8 cases, I had 6 broken bottles and all but 15-20 bottles that were 1/2 empty with frozen sludge from cap down. The other was an apparent infection that ended up spewing beer in the same manner (all bottles to some degree) and ended up with 2 broken bottles. Perhaps this is the exception and not the rule, but the only cases I've seen personally. Guess I'll be sticking with SA bottles!

[EDIT] No caps "popped off".......

@501

Got all that. What still had not been addressed is why we calculate based on a warm temp not the coldest temp the beer will reach (I'll call this MaxDiff - - if any mortar guys are out there, they'll get it). The beer will absorb the most CO2 at the coldest temp in our range, so why don't we calculate off that? Are people more afraid of under carbonation than over carbonation? I've never had under carbed beer, but have over carbed using several calculators.

Froggy22 said:

@501

Got all that. What still had not been addressed is why we calculate based on a warm temp not the coldest temp the beer will reach (I'll call this MaxDiff - - if any mortar guys are out there, they'll get it). The beer will absorb the most CO2 at the coldest temp in our range, so why don't we calculate off that? Are people more afraid of under carbonation than over carbonation? I've never had under carbed beer, but have over carbed using several calculators.

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My bad, I think I see where your going with this now. My assumption is that its for standardization reasons. If you start calling volumes at serving temperatures (would vary person to person), it would make sharing information more complicated........ best guess......

thehopbandit said:

1. Assuming gallons are the form of measurement, when a beer has 2.5 volumes of Co2, does this mean for every gallon of beer, 2.5 gallons of Co2 are dissolved in the liquid?

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Yes, 2.5 gal of CO2 at 1 atm and 20°C in every gal of beer.

thehopbandit said:

2. From my understanding, Co2 more easily dissolves into liquids at lower temperatures. How does this affect the amount of carbonation in the beer? For instance, if you bottle and condition at 66F and then later keep in the fridge at 35F, is the amount of Co2 in the liquid the same? Likewise, what would happen if the beer is stored at higher temperature? I'm just confused because the online priming calculators use bottling temp, but don't use storage/fridge temp so I am unsure how temps affect these numbers.

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Once the bottle conditioning has been done, and the CO2 has been created and absorbed into the beer, the carbonation in the beer really won't change significantly no matter what the storage temperature is. What will change significantly is the pressure in the headspace. If you think about the correct assumption you made in your first question it makes sense. If carbonation is simply the ratio of CO2 to beer, and the bottle is sealed, that ratio is going to stay the same regardless of temperature. Technically at warmer temps some of the CO2 will move from the beer to the headspace, decreasing the carbonation in the beer some, but the difference is minimal. The carbonation of the "bottle" will still stay the same.

thehopbandit said:

3. What is the max PSI a normal, 12 oz. glass beer bottle can hold?

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Depends a lot on the particular bottles. Most people agree that up to 3.0 vol is fine for most bottles, and 4.0 is flirting with disaster unless you're using nice thick belgian or champagne bottles. There are conflicting opinions and stories about carb levels in between.

thehopbandit said:

4. Obviously the carbonation levels in the bottle will not change based on temperature since the yeast produce X amount of Co2. What determines how much Co2 is in the liquid and how much is in the headspace?

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Temperature. But the headspace should represent a relatively small portion of the total volume of the bottle, so the amount of gas that moves between the headspace and the liquid is pretty small (within the relatively narrow temperature range that beers are served at).

For a general idea of what the CO2 absorbance is relative to temperature, take a look at one of the charts used for determining carbonation/serving pressure for kegging- http://www.kegerators.com/carbonation-table.php

If you wanted to, you could use that chart to determine the headspace pressure of your bottle conditioned beers (assuming your priming calculations were accurate).

Froggy22 said:

What still had not been addressed is why we calculate based on a warm temp not the coldest temp the beer will reach (I'll call this MaxDiff - - if any mortar guys are out there, they'll get it). The beer will absorb the most CO2 at the coldest temp in our range, so why don't we calculate off that? Are people more afraid of under carbonation than over carbonation? I've never had under carbed beer, but have over carbed using several calculators.

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The reason the calculators ask for the temp at bottling is so that it can account for the residual CO2 left in solution from fermentation. The temp you should actually input is the highest temp the beer reached after active fermentation stopped. If the beer stayed relatively cold, it will have held on to a substantial amount of the CO2. At 65° the beer will hold on to ~0.85 vol of carbonation if left undisturbed. If it warmed up, then much of that CO2 will have escaped, and the residual amount of carbonation will be much less.

If the beer fermented cool and never warmed up, and you don't account for the carbonation already present in the beer, you'll end up with overcarbed beer. Even knowing the temps it can be very difficult to accurately determine how much residual carbonation exists, because some will be lost transferring to the bottling bucket, and then more will be lost as it's transferred into the bottles.

As mentioned earlier, the carbonation level in the bottle isn't going to change for different storage temperatures. What will change is how much carbonation you're able to retain in the beer after pouring it. The warmer it is, the more the CO2 is going to want to escape, and the foamier the pour will be.