Co2 Volume

[pfitz]

G'Day all,

I'm trying to understand CO2 volumes, I know that I need to achieve 2.5 volumes for my beers but what does this mean?????

Does this mean that if I have a serving pressure of say 100Kpa, I need to force carbonate at 350 Kpa to get 2.5 Volumes?
How do you determine 2.5 volumes???


I may be a bit of a dummy, but this is all new and and I dont know where to go.

Been out to Craft Brewers a couple of times but they are always so busy with hordes of people I dont feel like asking a lot of dumb questions from a newbie and wasting thier time.

I've read the posts on force carbonation and it works but I want to understand why?


Any help would be appreciated.

Thanks in advance.

 

[Rowy]

I can tell you from experience the boys at Craftbrewer don't mind answering questions from noobs.

 

[donburke]

G'Day all,

I'm trying to understand CO2 volumes, I know that I need to achieve 2.5 volumes for my beers but what does this mean?????

Does this mean that if I have a serving pressure of say 100Kpa, I need to force carbonate at 350 Kpa to get 2.5 Volumes?
How do you determine 2.5 volumes???


I may be a bit of a dummy, but this is all new and and I dont know where to go.

Been out to Craft Brewers a couple of times but they are always so busy with hordes of people I dont feel like asking a lot of dumb questions from a newbie and wasting thier time.

I've read the posts on force carbonation and it works but I want to understand why?


Any help would be appreciated.

Thanks in advance.

beer, in fact most liquids, will absorb co2 into solution, i.e. the co2 will dissolve and become liquid in the beer

the amount of co2 absorbed is directly related to temperature and pressure, lower temp will absorb more, and higher pressure will absorb more

for a set pressure and set temperature the beer will absorb co2 up to what is called a saturation point, then it will not absorb anymore, this is what we try to achieve in a balanced keg system

this saturation point can be represented in a table or graph, that will let you look up a variable temp or pressure for a desired co2 volume (search for a carbonation chart)

 

[pfitz]

Thanks, but I understand pressure and temp will affect the amount of co2 in solution.

What I am trying to understand is (being a noob to all this), if say 2.5 @5 Deg is "x", what pressure is required to achieve "x".

Most charts sat you need a pressure of this or that for this period of time, force carbonation requires a pressure until no more absorbtion, whats that pressure?
Set to 300KPA, shake ,rattle and roll for a minute, let it settle back to 140KPA and Waalla, perfect!

I should mention that I have trouble brewing enough to get ahead of my drinking so this is important to me.

 

[michael_aussie]

Does this mean that if I have a serving pressure of say 100Kpa, I need to force carbonate at 350 Kpa to get 2.5 Volumes?
How do you determine 2.5 volumes???

beer, in fact most liquids, will absorb co2 into solution, i.e. the co2 will dissolve and become liquid in the beer

the amount of co2 absorbed is directly related to temperature and pressure, lower temp will absorb more, and higher pressure will absorb more

for a set pressure and set temperature the beer will absorb co2 up to what is called a saturation point, then it will not absorb anymore, this is what we try to achieve in a balanced keg system

this saturation point can be represented in a table or graph, that will let you look up a variable temp or pressure for a desired co2 volume (search for a carbonation chart)

and therefore the answer is "no you don't force carbonate at 350kPa if you want to serve at 100kPa".

The answer to this is far more complex than a simple pressure.

If you are going to force carbonate, the time you forcecarbonate is just as important as the pressure you force carbonate .. because as donbourke has explained there is a set amount of CO2 your beer will need to absorb to be balanced. Under normal circumstances this takes days to balance out. Force-carbonating is a commonly used "cheats" way to speed up this process. However, if you intoduce too much CO2 you will be pouring foam. Therefore the amount of time you forcecarbonate is very important. Overdo .. and you have form. Underdo and you have flat beer.

 

[seemax]

The 2.5 means 2.5g of co2 per litre.

The pressure needed to achieve this is a function of temperature.

Get the chart from google, select carb level, read pressure for desired temp. If you hook keg up at this pressure it will eventually reach your carb level.

 

[Wolfy]

What I am trying to understand is (being a noob to all this), if say 2.5 @5 Deg is "x", what pressure is required to achieve "x".

Most charts sat you need a pressure of this or that for this period of time, force carbonation requires a pressure until no more absorbtion, whats that pressure?
Set to 300KPA, shake ,rattle and roll for a minute, let it settle back to 140KPA and Waalla, perfect!

I have this chart printed and stuck on the side of my beer fridge, it has all the info you need:
http://www.aussiehomebrewer.com/forum//ind...st&id=17948

Simply set the pressure and temperature as indicated on the chart and give the beer some time to carbonate to the desired level.
For now, don't confuse yourself with force carbonation, which is more of a trial-and-error thing than mathematics that can be printed on a chart.

 

[donburke]

The 2.5 means 2.5g of co2 per litre.

no it isnt

its the ratio of co2 at atmospheric pressure over the volume of liquid its dissolved into

i.e. the 2.5 volumes equals 2.5 litres of co2 at atmospheric pressure dissolved per litre of beer

 

[glenwal]

I think what your refering to here is the Ross Method - where you force carb at a high pressure (say 300kpa), and then allow the pressure to drop back to a lower pressure (around 140-160kpa) as an indicatation of when it has absorbed enough CO2.

The idea here is you dial up the pressure to 300kpa and shake for a minute. You then turn off the gas and continue to rock the keg whilst watching the pressure on the reg. If the pressure drops below 140kpa, you add more gas and repeat. You keep going until it balances out at the pressure you wanted (between 140-160). There are no calculators to tell you what pressure to use, it is all trial an error. Give it a go using 140kpa, and if this isn't carbed enough for your liking, next time try say 145.

The important thing here though, is you don't serve at 140kpa. 140kpa is a pressure that helps you force carb consistantly. For serving, your pressure needs to be set around 85kpa (you can calculate this value) which is based on your temp and vols of C02 required (don't forget to release you PRV to drop the keg back to serving pressure). If your serving pressure isn't set correctly, your beer will slowly absorb more CO2 and become over carbed over the next week or 2.

 

[MHB]

Probably the best information is here Braukaiser
There is an equation that is easy enough to put into excel or similar and a couple of tables. If you want to understand carbonation go back a bit and read the whole carbonation section, a few of the people who have replied so far could use a refresher to!
Volumes of CO2 is a bit outmoded, most brewers outside the US use g/L which is all round an easier and better system, but roughly 1 Vol is 2 g/L.
Mark

 

[pfitz]

Thanks for the replies.

It seems that it was not a straight forward pump this much in at this pressure, let it rest at a given temp to get the required volume of CO2.

I like Ross's force carb method as I get to drink it faster, it works for me.
I suppose I was thinking of it not as Volumes or g/L but as a pressure related thing as this is all we've got to judge it. ie the pressure on the regulator.

Again, thanks for straitening me out.


Cheers.