Pressure in beer bottles - Home Brew Forums

 Home Brew Forums > Pressure in beer bottles

03-15-2011, 11:09 PM   #1
GoCardinals09
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Apr 2009
Denver, Co
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Does anyone know what the pressure in beer bottles is measured in? Is it PSI or amount of CO2 or something else? Also, what is the average amount of pressure in a bottle?

Thanks!!!

03-15-2011, 11:16 PM   #2
remilard
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Nov 2008
Kansas City
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The pressure is measured in psi, atm, bar, pascal or some other unit of pressure (force/area).

The amount of co2 is given typically as volumes or or grams per liter.

The pressure is only known if you know both the amount of co2 and the temperature.

03-15-2011, 11:54 PM   #3
nilo

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Aug 2009
Seattle, WA
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30psi.

See experiment at

http://beertech.blogspot.com/2009/12...tion-test.html

03-16-2011, 01:17 AM   #4
GoCardinals09
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Apr 2009
Denver, Co
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Quote:
 Originally Posted by nilo 30psi. See experiment at http://beertech.blogspot.com/2009/12...tion-test.html
That's very interesting!!!! I can't believe that there is over 30 PSI in the bottle. Do you remember at what temp you did your test at, before you threw them in the fridge?

Cheers

03-16-2011, 01:28 AM   #5
nilo

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Aug 2009
Seattle, WA
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room temp in my garage, probably 60 to 65F.

03-16-2011, 01:56 AM   #6
Ernst-Haeckel
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Nov 2010
MA, MA
Posts: 117

To nilo:

So, basically, your experiment shows that the tensile strength of plastic is greater than 36 psi, since that is the pressure you attained without bottle failure. Regarding bottle bombs, you now need to determine what the tensile strength of a glass bottle is. As long as the tensile strength of a glass bottle is less than 36 psi, no bottle bombs!

Great experiment! As a material scientist, I am entertained by your experiment! Keep it up!

You should also consider a measure of yeast attenuation for each experiment. Measure the gravity of the sample before pressurization and after the experiment to determine exactly how much of the 3 or 6 grams of sugar was converted to CO2 and alcohol. The results will then be a bit more interesting. I do love to see how the pressure decreases with temperature, though! PV=nrT!

03-16-2011, 02:06 AM   #7
nilo

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Aug 2009
Seattle, WA
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Just FYI, the same beer and prime sugar that went into those PET bottles also filled glass 22oz bottles. That was a regular 5gal batch, so I filled about 20-22oz glas bottles. None exploded, so I assume all were able to stand 36psi.