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Old 01-20-2012, 03:21 AM   #1
Marshi
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Default Temperature questions

Two questions relating to temperature, though not particularly related:

First and most importantly: what is the correlation/relationship with temperature and CO2 levels in beer when carbonating? This mostly applies to brewing at a relatively large scale where one is infusing CO2 to carbonate, but when one increases temperature what happens to the level of CO2, and vice versa? When do you know you have a right balance of the two?

Second question: does temperature affect pH levels in water? I have been taking pH samples of my mash, and I'm not sure if I should modify my pH readings based on temperature.

Yee!

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Old 01-20-2012, 03:38 AM   #2
day_trippr
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Here's a carbonation table to study. It shows the relationship between temperature and CO2 pressure wrt levels of carbonation. As temperature increases it takes more CO2 pressure to provide the same level of carbonation as lower temperatures.

As for your second question, the short answer is "yes" - at least wrt measuring pH...

Cheers!

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Old 01-20-2012, 05:29 AM   #3
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Quote:
Originally Posted by Marshi View Post
First and most importantly: what is the correlation/relationship with temperature and CO2 levels in beer when carbonating?
Vols ~ (P +14.695)*(0.01821 + 0.090115*exp(-(T-32)/43.11))

Temperature is in °F and pressure in psig.

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Originally Posted by Marshi View Post
This mostly applies to brewing at a relatively large scale where one is infusing CO2 to carbonate, but when one increases temperature what happens to the level of CO2, and vice versa? When do you know you have a right balance of the two?
It equally applicable when carbonating in the keg. One decides how many volumes he wants and knowing what temperature he is storing at uses the formula (or a graph or table derived from it) to determine the pressure

P = Vols/(0.01821 + 0.090115*exp(-(T-32)/43.11)) - 14.695


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Originally Posted by Marshi View Post
Second question: does temperature affect pH levels in water?
Yes but it depends very much on the chemistry of the water. The answer is simple for very pure water. At 20 °C the pH is 7.08, at 25 °C 7.00, at 30 °C 6.92 etc. Pure water which has been exposed to air will immediately take up CO2 from the air which causes the pH to drop. How much depends on the temperature. At 20 °C it will go, eventually (which may be days) to 5.66; at 25 C to 5.67 and at 30 °C to 5.69. For water with things other than CO2 dissolved it is necessary to know the chemistry of the particular sample before pH variation can be calculated.

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Originally Posted by Marshi View Post
I have been taking pH samples of my mash, and I'm not sure if I should modify my pH readings based on temperature.
This is really a separate question. You should not be modifying your pH readings based on temperature. What you should do is make all your readings at the same temperature. Room temperature is the obvious choice. You should also record what that temperature is and this is because the mash of the pH does change slightly with temperature (about -0.005 pH/°C). Thus if you record 5.40 in a measurement made at 20 °C and then check 20 minutes later and read 5.39 in a sample cooled to 22 °C you would not worry about the change of 0.01 (not that you would anyway) as it is explained by the differences in temperature - not any change in the mash chemistry. This assumes that the meter's ATC feature is turned on and working as the response of the electrode depends on temperature and this effect must be compensated.
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