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-   -   Do higher pressures carbonate faster? (http://www.homebrewtalk.com/f35/do-higher-pressures-carbonate-faster-173501/)

copela 04-16-2010 02:05 AM

Do higher pressures carbonate faster?
 
I'm wondering if beer carbonates faster at higher pressures, or if the CO2 dissolves at a constant rate no matter what the head pressure?

Does anyone know the science behind this?

I work at a homebrew shop and we have been having a debate on this. Some of the folks here have been turning up our regulator to about 35PSI to carbonate one beer, but we have splitters feeding up to 4 or 5 kegs at a time so they all end up getting overcarbonated.

They think the beer will carbonate faster, but I think the gas diffuses at a constant rate, and this just ends up overshooting the target carbonation level. I understand about gas dissolving more at lower temps and all that business. But I think the gas would diffuse into the beer at whatever level is dictated by the temp and the gas content of the beer. Can someone tell us if this is right?

goose1873 04-16-2010 02:09 AM

higher pressure will carb faster...Ex: if i set it and forget it at 12psi it takes weeks. at same temp if i set at 30psi for 48hrs then purge and set to pour psi...perfect in 2 days...

copela 04-16-2010 02:36 AM

Thanks for the reply goose. But I have also had beer carbonate at 12 psi within a few days. I usually use about 12psi, and the next day there are light bubbles but not much, but then by day 2 or three we are drinking it with (at least close to) normal carbonation.

Yooper 04-16-2010 02:42 AM

I've never had beers carb up at 12 psi in three days. Never. It takes about 10 days before I get a bubbly beer.

Now, at 30 psi for 36 hours- I have a carbed up beer. If I'm in a real hurry to drink a beer, I stick it in the kegerator at 30 psi overnight, check it the next day, and see. If it's close, I purge and turn it down to 12 psi. Usually, though, it takes about 36 hours. It's fully carbed in that time for certain. Then I purge and reset to 12 psi.

Really, it would be better for my system to leave it alone at 12 psi and just come back in a week. I just can't seem to help myself- I just want to sample it way too early!

remilard 04-16-2010 02:47 AM

Quote:

Originally Posted by copela (Post 2008486)

Does anyone know the science behind this?

I work at a homebrew shop

Go pick up a copy of Principles of Brewing Science and read the appendix on draft beer.

lamarguy 04-16-2010 02:53 AM

Quote:

Originally Posted by copela (Post 2008486)
I'm wondering if beer carbonates faster at higher pressures, or if the CO2 dissolves at a constant rate no matter what the head pressure?

As others stated, yes, higher pressure yields more dissolved CO2 in a shorter time period. But, surface area, agitation, and temperature also dictate how fast and how much CO2 the liquid will absorb.

Think about a soda machine - it operates at 100 psi and uses a high liquid-to-gas surface area to rapidly carbonate room temperature water as it passes through a ~2 gallon tank. If the incoming water was at, say, 38F, you could lower the pressure to ~60 psi and still produce the same level of carbonation in the same amount of time.

malkore 04-16-2010 06:58 PM

I too never get full carbing at 12psi until at least 7-10 days.

Higher pressure and lower temps will increase gas solubility in the beer (faster carbing). it also becomes way too easy to over carb. That's why I just set it and forget it (but I don't drain kegs very fast either, so I have the luxury)

Bobby_M 04-16-2010 07:47 PM

I don't get full carbonation at set and forget pressures for nearly 3 weeks. The carbonation difference between week 2 and 3 is probably .5 volumes, but it confirms that rate of absorption is not linear. Rate of absorption is proportional the delta between the partial pressure between the head space and the gas dissolved already. Long story short, 40psi will hit 2 volumes about twice as fast as 20psi.


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