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Old 10-27-2008, 07:50 PM   #1
Joetuo
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When you brew with colder temperatures does your boil off per hour go up or down?

 
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Old 10-27-2008, 08:01 PM   #2
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I was gonna ask the same question. When I started boiling yesterday I had 7 gallons. When I finished my boil(90mins) I had a touch over 5 gallons. Do I have the flame up to high or does it really matter?? Sorry for the highjack...
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Old 10-27-2008, 08:32 PM   #3
broadbill
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boil rate goes up. IIRC, it has something to do with the ability of cold air vs. hot air to hold moisture. Cold air has less moisture in it, which increases the rate at which moisture is transfered from the boil pot to the air.

hope this helps...I'm sure someone else will chime in with a better worded explanation.

 
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Old 10-27-2008, 08:34 PM   #4
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I did a brew one time in Arizona in the summer. It was about 105 with no humidity. My boil rate was much higher than normal. The humidity in the air will affect the rate not just the temp.
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Old 10-27-2008, 08:41 PM   #5
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It has to do with the fact that in the winter the air is usually much drier and therefor will hold and absorb more moisture. Also I believe that cooler air has the potential to hold more moisture just because the air is denser.
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Old 10-27-2008, 08:45 PM   #6
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Warmer air holds more moisture. When it gets cold, the vapor condenses and forms a liquid again. It's why there's dew on everything in the morning.
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Old 10-27-2008, 08:48 PM   #7
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i'm in the same boat! lost way more than I was planning on with my boil yesterday. for some reason, the cooler temps hadn't dawned on me as a potential reason. DUH.
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Old 10-27-2008, 08:51 PM   #8
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this would explain my weekend session as well
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Old 10-28-2008, 07:32 PM   #9
Joetuo
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Ok so I will have to take into account that my boil off per hour will be higher then during the summer months. How much more do you think the cold temps affect it? up to 2 gals per hour?

hmm mods can you move this thread meant to put it in General Beer discussion,since this isn't just AG, must have clicked the wrong forum yesterday...thanks

Reason: added the wrong forum msg for mods

 
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Old 10-28-2008, 08:06 PM   #10
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I'm not so sure that ambient air temperature in and of itself gives a higher evaporation rate. The main factors that effect it are relative humidity and air movement (breeze, wind). There is a "boundary layer" at the surface of the liquid being boiled. At this layer, the liquid is evaporating. The colder the air temperature, the more the evaporating liquid at the boundary layer has a chance to condense and fall back into the liquid. So, by that logic, all other things being equal, colder air temperature would cause less evaporation.

But still, I think humidity and air movement have a bigger impact here. The highest evaporation rate would be seen in a hot, dry, windy desert-like condition. If you took these same conditions (keeping air movement and relative humidity the same) and only lowered the air temperature, you'd actually get less evaporation because of more condensation occuring at the boundary layer. It just so happens that for those of us in a temperate climate, it's common to see the breeze pick up and the relative humidity go down with the seasonally cooler temperatures... giving us a higher evaporation rate than on a calm, relatively humid summer day.

If I'm way off here, call me out... I pulled that out of my a$$.
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