Converting volumes of CO2 to PSI?

[Calypso]

I emailed EZ Cap (the makers of the EZ Cap swing-top style bottles) and ask what pressure their 1 liter bottles were rated to. They replied that they are rated for up to 100 PSI. How do I convert a given carbonation level (3.3@70F, let's say) into PSI?

 

[conneryis007]

googled this for you:
http://www.kegerators.com/carbonation-table.php

 

[tootal]

There are many charts out there showing Volumes of CO2. It all has to do with the temp. of the beer and the pressure it's under. You want it to be correct for the style and the temperature you're going to serve it at.

An example would be a 40 degree beer at 12 psi would be around 2.3 - 2.5 Volumes of CO2. That's off the top of my head but I'm sure it's close.

This will be good for most beers. The colder the beer the less pressure it needs to achieve a certain Volume of CO2.

http://www.kegerators.com/carbonation-table.php

So the chart goes to 65 degrees and a Volume of CO2 of 2.5 would be achieved at 28 psi.

 

[Calypso]

googled this for you:
http://www.kegerators.com/carbonation-table.php

I saw that chart, but I wasn't sure if it was somehow specific to the volume of a keg? So I can use the keg pressure calculators out there and it will give me a reasonably accurate number?

 

[Calypso]

And sorry, I don't mean to harp on this, but isn't pressure dependent on the volume of the vessel? So wouldn't a 1 gallon container of beer have less internal pressure than a 5 gallon container of beer? Otherwise, it seems like conditioning in growlers should work without issue.

 

[day_trippr]

The CO2 pressure setting has nothing to do with the volume of beer being carbonated, and everything to do with the temperature of the beer and the desired level of carbonation.
As well, the amount of pressure exerted by a carbonated beverage on a sealed vessel doesn't change with volume, either. A 12 ounce beer has the same head space pressure as a "full" five gallon keg if both beers were carbed to the same volumes of CO2.

In short: just use our favorite carbonation table, and allow a couple of weeks under the appropriate constant pressure to get 5 gallons of beer in a corny keg carbed to goal. It works...

Cheers!

 

[MrFoodScientist]

And sorry, I don't mean to harp on this, but isn't pressure dependent on the volume of the vessel? So wouldn't a 1 gallon container of beer have less internal pressure than a 5 gallon container of beer? Otherwise, it seems like conditioning in growlers should work without issue.

This is only true if they contain the same volume of beer, and you have it backwards, smaller vessel (assuming same volume) = greater pressure.

Growlers aren't rated for the pressure of conditioning at room temperature. I'm sure conditioning in this would work just fine:

and it's way bigger than a growler, or a corny for that matter.

 

[audger]

And sorry, I don't mean to harp on this, but isn't pressure dependent on the volume of the vessel? So wouldn't a 1 gallon container of beer have less internal pressure than a 5 gallon container of beer? Otherwise, it seems like conditioning in growlers should work without issue.

pressure is dependent on the amount (mass/relative weight/'pounds') of gas present, and the size/volume of the container it is in, yes.

However, since the unit of measure is not sheer weight (simple 'pounds'), but PSI (pounds per square inch), the spatial/volumetric parts of the math formula have already taken into consideration when measuring in PSI. Its all about the ratio of pressure to surface area, which PSI measures.

5psi in a 12oz beer bottle is 5psi in a 5gallon keg; there is just more *mass* in the keg... same pressure ratio.

so to answer the question

So wouldn't a 1 gallon container of beer have less internal pressure than a 5 gallon container of beer?

the number of "pounds per square inch" is the same; the smaller container just contains less mass (actual "pounds"; irrespective of container volume) of gas, obviously.

If you were to take the same mass of CO2 in a 12oz bottle, and put that mass into a larger container, sure the pressure would be lower because the same amount of gas will fill a larger area. If PSI is held constant, the amount(mass) of gas will have to change with container volume. Likewise, if mass is held constant, PSI will decrease with increasing container size. Make sense?

 

[Bobby_M]

The chart is perfectly suited for reversing the calculation. If you know volumes and temp, you can find out what PSI will be present in an already carbed container of beer. In other words, you can use the chart to figure out what pressure you need to apply to reach a certain volume of CO2 given a known beer temp.

 

[DSorenson]

A known volume of CO2 enclosed in a known space at a known temperature will give you a known pressure.

If we consider beer to be essentially incompressible, we know that the only place for CO2 to go is in the headspace of the bottle. Let's also assume that the bottle is an ideal pressure container: that is that it doesn't flex or stretch, and that it doesn't have any points of weakness. I just checked the volume of a head space of one of my glass 12 oz bottles to find out that there is almost exactly 30 mLs of volume in the space itself.

Now I just need to know what a "Volume of CO2" is really a measurement of.

 

[Calypso]

Make sense?

Clear as mud.

The chart is perfectly suited for reversing the calculation. If you know volumes and temp, you can find out what PSI will be present in an already carbed container of beer. In other words, you can use the chart to figure out what pressure you need to apply to reach a certain volume of CO2 given a known beer temp.

Great. As long as I can rely on those charts/calculators, I'm happy.

So if their bottles are rated up to 100 PSI, I could do over 5 volumes of CO2 at 70F (in theory, I have no plans to do so.)

 

[dyqik]

Now I just need to know what a "Volume of CO2" is really a measurement of.

It's the volume that the CO2 gas dissolved in the beer would occupy at standard temperature and pressure, relative to the volume of the beer. A beer carbonated to 2.3 vols contains 2.3 times it's own volume of CO2 gas.

 

[Bobby_M]

A known volume of CO2 enclosed in a known space at a known temperature will give you a known pressure.

If we consider beer to be essentially incompressible, we know that the only place for CO2 to go is in the headspace of the bottle.

Except when the CO2 starts dissolving into the beer, which is what carbonation is.

If you have a container that holds 11 gallons and it's full of 10 gallons of beer, your headspace to liquid ratio is 1:10. If you instantanously put 100 psi into the headspace and remove the source of gas, you can expect the total pressure to equalize at 10 psi eventually. Even though it starts at 100psi in the head space, it eventually occupies the full container volume.

 

[DSorenson]

Wow thanks guys. That's pretty interesting... so time is a factor because eventually the gas dissolves throughout the beer, equalizing the pressure between the headspace and the beer itself.

I was clearly heading down the wrong path there... and I call myself an engineering student.

 

[monkeybox]

If you have a container that holds 11 gallons and it's full of 10 gallons of beer, your headspace to liquid ratio is 1:10. If you instantanously put 100 psi into the headspace and remove the source of gas, you can expect the total pressure to equalize at 10 psi eventually. Even though it starts at 100psi in the head space, it eventually occupies the full container volume.

This math seems way too easy/magical to be true. It also doesn't take into account existing co2 in solution, which has to play a role (otherwise you could store an infinite amount of co2 in beer, since you could repeat the above procedure as nauseun).