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Temperature Inside Fermenter

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Hophazard

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Hey all! Been reading the site for a while and I finally have a question that I couldn't find an answer for. I'm pretty new to brewing, having brewed two extract batches of pale ales so far (nothing bottled yet), but have to say this is definitely something I see myself doing pretty regularly.

I've read a lot of threads about the temperature for fermenting, but didn't see anything about people testing the temp inside the fermenter. Obviously I know that regularly opening the lid is discouraged and can lead to potential contamination, but it appears that the temp in the primary is a lot higher than the ambient temp while fermentation is happening (e.g. when it's 70F where the beer is sitting, the temp strip on my primary will say 72-74F). As an FYI, the temp strip and my other thermometer give identical temp readings when the primary is empty.

I just want to make sure that I'm not letting the beer inside the primary get to the higher end of the temp spectrum since apparently it will lead to fruity flavors in the final product.

Thanks for any help. Looking forward to hearing from everyone!
 

trimpy

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If you want to safely measure the temp inside the fermenter, may i suggest one of these:

 

rsmith179

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From my own experience, it does appear that the beer is a few degrees (5-10F) warmer in the fermenter than the ambient air temp is. This is probably due to the reactions occurring inside the fermenter. At least this is what I would assume. You may want to bring the heat down just a little bit if possible to ensure that the beer is at the correct temperature, not the air.

I do agree with Trimpy too. You could always get a thermo that goes directly into your beer and you could use that with a Love temp controller to control the heater in that room to ensure that your beer is at a consistent temperature.
 

carnevoodoo

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From my own experience, it does appear that the beer is a few degrees (5-10F) warmer in the fermenter than the ambient air temp is. This is probably due to the reactions occurring inside the fermenter. At least this is what I would assume. You may want to bring the heat down just a little bit if possible to ensure that the beer is at the correct temperature, not the air.

I do agree with Trimpy too. You could always get a thermo that goes directly into your beer and you could use that with a Love temp controller to control the heater in that room to ensure that your beer is at a consistent temperature.
Yeast respiration is an exothermic process, so you are going to generate heat. You will want to keep your temps under control. As for those stick on thermometers, they're pretty accurate. Most people say within a degree, so if you have them you might as well use them. I trust mine.
 

menschmaschine

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If you get a small probe thermometer and attach it to the outside of your fermenter with tape and several layers of bubble wrap for insulation, you'll get a very close measurement of the temperature inside the fermenter.
 
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Hophazard

Hophazard

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Yeast respiration is an exothermic process, so you are going to generate heat. You will want to keep your temps under control. As for those stick on thermometers, they're pretty accurate. Most people say within a degree, so if you have them you might as well use them. I trust mine.
Cool - I haven't seen the temperature rise above 74, so hopefully it's fine. I just wanted to make sure that I wasn't ruining these first two "practice" brews (at least at the fermentation stage; I'm sure I'll have plenty of opportunity to do that with bottling, etc.).
 

carnevoodoo

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Cool - I haven't seen the temperature rise above 74, so hopefully it's fine. I just wanted to make sure that I wasn't ruining these first two "practice" brews (at least at the fermentation stage; I'm sure I'll have plenty of opportunity to do that with bottling, etc.).
Well, I would suggest getting them a little lower moving forward. 74 is a little warm and you're likely to get some esters. It is nowhere near as bad as a beer at 80 degrees, but it will be there.
 

flyfishnc

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wouldn't one of those 'stick-on' thermometers work to measure the temp inside? i imagine the temp in the middle of the wort is pretty dang close to the outer edges. just a thought, i'm new at this so i may be way off base...
 

carnevoodoo

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wouldn't one of those 'stick-on' thermometers work to measure the temp inside? i imagine the temp in the middle of the wort is pretty dang close to the outer edges. just a thought, i'm new at this so i may be way off base...
I think that's what I just said. :)

Yes, the stick on thermometers are great.
 
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Hophazard

Hophazard

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Well, I would suggest getting them a little lower moving forward. 74 is a little warm and you're likely to get some esters. It is nowhere near as bad as a beer at 80 degrees, but it will be there.
Agreed. Going forward, I'll be sure to lower the temp even more. I kept the air at 70 during the process, but didn't account for the internal rise in temperature. Once I saw that the stick-on read 74 degres, I immediately turned down the temperature. 74 was the warmest it got, and not for very long, so hopefully all is well inside.
 
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Cool - I haven't seen the temperature rise above 74, so hopefully it's fine. I just wanted to make sure that I wasn't ruining these first two "practice" brews (at least at the fermentation stage; I'm sure I'll have plenty of opportunity to do that with bottling, etc.).
+2 for getting the temps down, i would shoot for under 70, lower depending on the style/yeast. putting the bucket/carboy in a water bath with some ice is a good way to do it if you cant control the air temp in the room.
 
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