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Old 07-24-2008, 10:58 PM   #1
oberon567
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Default Ambient Temperature vs. Wort Temperature

So, now I am all stressed out. And I dont have any homebrew to RDWHAHB. Here is the deal.

This last weekend I brewed 15 gallons of beer, three different recipes. I am still relatively new, these three batches put me hovering somewhere around 15 - 17 batches. I realize now that one of my biggest problems in the past has been fermentation (and pitching) temperatures, and so I really wanted to control that as much as possible starting from now on.

It still takes me along time to cool my wort to an acceptable pitching temp, even with soaking in an ice bath and a wet t-shirt and an A/C. By the time I ended up pitching, I pitched all of these low, 61 - 64 degrees. I know this might knock out some of the yeast, but I figured it would be OK, especially as the act of fermentation produces some heat anyway. For all of them I pitched a starter, 1.5 - 2 liters, that had been going for about 18 - 24 hours or so.

All three of them are in my bedroom with the A/C on low, all day long. Using a standard outdoor, alcohol thermometer, this keeps my ambient temperature right around 66 - 69 degrees, which I figure is perfect, enough to warm the yeast up and hopefully prevent fusel production.

Well, I have been reading more and more and listening more and more about the importance of temperature, and decided to check the temp of my brew/wort by removing the airlock and sticking my sanitized probe thermometer in the hole in the lid. I know, this introduces a bit of oxygen and potential for baddies, but figured it would be worth the check, because if they're too cold the yeast might drop out, and these are all 6 - 10ABV beers. I only did this two two of the brews, and the readings came back at 59 and 57. Which is ridiculously low for an ale, I know. I didnt expect the ambient temperature to be so radically different than the actual temperature!

Then I remembered that one of my buckets has one of the sticky thermometers on the outside, which I never look at because I don't trust it. It says that the soon-to-be beer inside is 73.

So now I am really, really confused and not sure what to do. On one hand, I would rather the ferment take a long time and I need to re-pitch more yeast to finish and clean up the Acetaldehyde than the production of fusel alcohol.

I can make the A/C colder, or I can run it at a lower temp, or I can turn it off. But I have no clue what I should do.

I know that I should just wait and be patient and check my FG to ensure that fermentation is done. Well, it isnt even time for that yet, the oldest brew is less than 7 days old, so that is a few days in the future. But in the meantime, what the hell is happening?

If the ambient temperature is 67, what should I expect the actual temperature of the brew to be? What can I do for better regulation?

Thanks for your time and advice!

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Old 07-25-2008, 12:59 AM   #2
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I think you have a problem with your probe thermometer. Maybe it is out of calibration. Trust the ambient thermo and the strip on the bucket. They are in a pretty good range for ales. Let it go another week or longer. You will be fine.

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Old 07-25-2008, 01:00 AM   #3
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Relax. Ambient of 67 is just fine. While the limit where off-flavors begin is debatable, I think you're quite safe up to the mid 70's. Mine is bubbling at at 68-70 right now.

As a further guard against off-flavors, you could try yeasts like Nottingham or S-05 that finish with a clean flavor profile.

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Old 07-25-2008, 01:33 AM   #4
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Thanks for the solace!

If the ambient is 68, what would I expect the actual temperature for 5 gallons in an Ale Pail to be? I am assuming this should be pretty standard regardless of the type/density of beer... IE, storing in a 68 degree room = 70 degree beer, or something like that...

In my head, there would be a complete equilibrium, at least eventually, ie 68 temp = 68 actual. But today I was thinking about the fact that fermentation is an exertion of energy and hence a production of heat, so I decided to check, and, lo and behold, got all nervous.

I hope my probe thermometer is not out of whack, that means I have mashed the last three brews, (well only two of them were PM) at an entirely wrong temp. Though my OGs came out to be pretty close to the recipe calculators online. I will have to check the calibration... I think there is actually another active thread about this very thing right now...

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Old 07-25-2008, 01:39 AM   #5
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Quote:
Originally Posted by oberon567 View Post
Thanks for the solace!

If the ambient is 68, what would I expect the actual temperature for 5 gallons in an Ale Pail to be? I am assuming this should be pretty standard regardless of the type/density of beer... IE, storing in a 68 degree room = 70 degree beer, or something like that...

In my head, there would be a complete equilibrium, at least eventually, ie 68 temp = 68 actual. But today I was thinking about the fact that fermentation is an exertion of energy and hence a production of heat, so I decided to check, and, lo and behold, got all nervous.

I hope my probe thermometer is not out of whack, that means I have mashed the last three brews, (well only two of them were PM) at an entirely wrong temp. Though my OGs came out to be pretty close to the recipe calculators online. I will have to check the calibration... I think there is actually another active thread about this very thing right now...
Well, there isn't any standard in the temperature of ambient vs the wort temperature- and that's because it varies. Fermentation is exothermic. So, a fast and furious ferment might cause a temperature rise of 10-12 degrees inside the carboy. A slow but steady fermentation might cause a rise of 2 degrees or so. I now have my primaries on the basement floor- on the concrete. The ambient is mid-60s, but the (now finished) beer is low 60s because of the nice cold concrete. The fermometer strips are pretty darn accurate, or you could use an aquarium thermometer strip instead- those are +/- a degree or two.

I think you'll need to check your calibration on the probe thermometer.
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Old 07-25-2008, 01:45 AM   #6
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Well, there isn't any standard in the temperature of ambient vs the wort temperature- and that's because it varies. Fermentation is exothermic. So, a fast and furious ferment might cause a temperature rise of 10-12 degrees inside the carboy. A slow but steady fermentation might cause a rise of 2 degrees or so. I now have my primaries on the basement floor- on the concrete. The ambient is mid-60s, but the (now finished) beer is low 60s because of the nice cold concrete. The fermometer strips are pretty darn accurate, or you could use an aquarium thermometer strip instead- those are +/- a degree or two.
Thanks, that makes sense. Once the science is explained things fall into line a little more for me.

And one of those three brews is your DFH60 clone, which I am really excited about it!
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Old 07-25-2008, 01:52 AM   #7
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Sounds like you have two different areas of temps that you want more control over...getting down to pitching temps and then fermentation temps. Your doing PMs but are you partial boils or full boils? Lots of options either way....

As far as fermentation temps, Palmer reports that wort temp can be up to 10 degrees warmer than ambient due to yeast activity. The temp on your strip thermometer sounds closer to the actual fermentation temp all things considered. While 73 might not get to excessive fusel production, you may notice increased ester production...have you sampled your recent batches and noticed anything unusual that could be due to higher fermentation temps or the probe thermometer error? You might want to consider leaving this one in the primary for a little more time than usual to let the yeast clean up a bit.

Again, lots of options depending on what you want to do and level of effort. On the cheap I have used water baths (w/ ice packs if necessary) & a t-shirt over the carboy w/ a fan aimed at the carboy to keep temps down in low-mid 60s during initial fermentation stages. I just built a "son of fermentation chiller" for this summer to really keep a tight leash on my temps.

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Old 07-25-2008, 02:25 AM   #8
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I added another grommet to the lid,
then I epoxied a bit of copper tubing to my digital thermometer.
Now I can check temps as often as I like without opening up.

With 68* ambient and a nice cool concrete floor, my last batch peaked at 73*.
On the fourth day, it was back to 68*.

I've heard the '10-12* above ambient' before.
I think that's the extreme, not average.
Also, small batches probably shed heat faster than large ones.

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Old 07-25-2008, 02:48 AM   #9
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I built a "son of fermentation chiller" last weekend for an IPA I was doing. I put a thermometer in the chamber and a controller probe on the glass carboy with a 1 inch thick piece of neoprene between it and the ambient air. The beer had an OG of about 1.065 and was kept at 67.x degrees during fermentation. To achieve this temperature in the fermenting wort the ambient hovered around 62 degrees. It stayed that way for about 3 days and now there is only a couple degree difference on the 4th day.

So, for the IPA that I brewed last Sunday there was a difference of about 6 degrees. First time I paid this much attention to it since I had been warming my beers in the basement until now, finally got too warm down there.

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Old 07-25-2008, 03:18 AM   #10
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Yeah, I have temperature issues all over the place.

I do PM and do 3 - 3.5 gallon boils, adding cold water to finish out the 5 gallons.

For all three of these batches I have put them in an ice bath with a wet t-shirt in the air conditioned room. It still took hours and hours to lower down to a decent pitching temperature. (I put the sanitized lid on loosely, to at least give the semblance of sanity).

I know that I need to figure out a better method. MOney is short, as are supplies and equipment. I am working on it, though!

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