Author Topic: Exothermics and Fermentation  (Read 6569 times)

Offline Wildrover

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Exothermics and Fermentation
« on: July 22, 2009, 08:08:54 AM »
We know that the fermentation process can raise the temp of the wort but does anybody know how much?  I know Palmer says "up to 10 degrees"  I believe on page 87 but this is to general of a number for me to be comfortable with.  Does anybody know of any formula that will better ballpark the temp rise due to fermentation? 

Offline MaltLicker

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Re: Exothermics and Fermentation
« Reply #1 on: July 22, 2009, 04:37:10 PM »
No, but I imagine that varies wildly by shape of the ferm vessel and volume, and may once have played a role in how certain beers were created.  Big flat coolships, square top-cropping, and now all shapes of s/s conicals.  I think in Brew Like a Belgian they described the many, many batches brewed somewhere when they 'upgraded' their ferm equipment and they wanted to ensure the beer stayed the same. 
On our scale it may vary even more since we lack great cooling control compared to pros.
Someone could probably figure the heat dissipation from the center to outer edge based on volume and diameter, but how to accurately calculate the heat generated........strain, starter size, O2, OG, volume, sugar profile, ambient temps, phases of moon.   

Remove airlock and stick a thermo (rubberbanded to a tube) down the center?  Repeat as necessary?   :-\

Offline UselessBrewing

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Re: Exothermics and Fermentation
« Reply #2 on: July 23, 2009, 08:58:47 AM »
I agree that there are way to many factors that come into play to get an accurate reading. I use a Glass thermometer and it has an immersion mark which means I can only suspend it three inches into the wort durring fermentation. Which for me would not be close enough to the center of the beer, also how would you take a reading on the edge of the beer. Reading the Glass/Plastic on the outside, IMO, would not be an accurate reading of the beer inside.

my 2c.

Cheers
Preston
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Offline Wildrover

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Re: Exothermics and Fermentation
« Reply #3 on: July 23, 2009, 06:49:07 PM »
If you do have temp control, like a fridge of some sort and a temp controller, do you set the temp lower than what you want the beer to ferment at?  If so, what do you set the control at?

Offline UselessBrewing

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Re: Exothermics and Fermentation
« Reply #4 on: July 24, 2009, 08:29:01 AM »
When I lager in my beer Fridge, I set the temp at the bottom end of the yeast range. There is no way of knowing what the center would be so I just let it go.

Cheers
Preston
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Offline MaltLicker

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Re: Exothermics and Fermentation
« Reply #5 on: July 24, 2009, 07:58:57 PM »
I have a small (7ft?) chest freezer, fairly new, with digital thermo controller.  Since it's new and relatively tight around the glass carboy, I set the thermocontroller for 2F lower than I want the ferm to be during the first 2-3 days, then raise it a couple after the heavy lifting is done.  Typically for ales, this means 64/65 initially and then 67/68, depending on yeast and beer style.  If the yeast can go lower, and I expect a hot start, I have started as low as 62 and raised 1F per day after the 2-3 day.  I've learned the hard way that fusels don't go away (before chest freezer), so I'm probably overly cautious. 

The fish-tape thermo on the glass indicates that I'm keeping the outside in my range, but who knows what's happening in the center.  I do spin it on the lazy susan gadget to spread the heat around, and figure with the  tight confines that I'm doing the best I can. 

Offline SleepySamSlim

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Re: Exothermics and Fermentation
« Reply #6 on: July 25, 2009, 12:31:53 AM »
I picked up a digital temperature controller and a rubber stopper with a 15" stainless steel sealed temperature well (for the temp. probe) and a second hole for the airlock. I use a plastic BrewCraft 7Gal bucket that has a temperature strip on it. My observations show a delta of 1 to 1.5 degrees between the center of the bucket and the strip in the side.

I'm not sure if thats a true delta between the inside and outside - or its the temperature lag between the inside and outside. Most likely a little of both  
« Last Edit: July 29, 2009, 02:21:40 AM by SleepySamSlim »
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Offline Wildrover

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Re: Exothermics and Fermentation
« Reply #7 on: July 25, 2009, 03:49:24 PM »
I appreciate all the input.  This is an area I haven't thought much about because its all I can do just to keep the wort reasonably close to fermentation temp.  However, I hope to have some control fairly soon so I was curious as to how people handle the difference or if its even enough of a difference that its something you need to worry about

Offline MaltLicker

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Re: Exothermics and Fermentation
« Reply #8 on: July 27, 2009, 03:50:46 PM »
.................My observations show a delta of 1 to 1.5 degrees between the center of the bucket and the strip in the side.

I'm encouraged that actual data indicates the center may not be the inferno Palmer suggests.  And it makes me like the lazy susan gadget even more.  I've been spinning my robust porter every few hours to spread the yeast and the heat around.  For a $5 toy, it has many benefits.  See attached photo; available at WoodCrafters stores.  The 9-inch size fits carboys great.