Fermentation Temps

Been brewing for several years now....started All Grain last year.....and until now I haven't really thought much about this but.....here is my question:

When a recipe calls for a fermentation temperature.....or brewers talk about fermenting at a certain temperature......I have always done the following.

Lets suppose the recipe says to ferment at 68F....

To me that means cool my wort down to 68F....pitch my yeast....and stick my ale pail/carboy in a my fermenter with a setpoint temperature (ambient in fermenter) of 68F.

But....with the yeast activity the wort temp could be 3-4 degrees (even more) above ambient.....so if my starting wort temp = 68F....it will reach 71-72F maybe......so with this in mind should the ambent temp be 3-4 degrees below the fermentation temp recommended in the recipe, etc.....i.e. in this case set fermenter temp to 65F.

THis may not matter in most cases....but for some beers like a Hefeweizen where the fermentation temp can really effect the flavors (i.e. more banana or more clove...etc) this could be a big deal.

Any thoughts on this?

Im in the same boat, been brewing for 2 years and just started to monitor ferm temps more closely. Just finished 2 seperate ferm rooms so we can have multiple beers fermenting, crashing, or aging at the same time. We used a previously installed exhaust fan in reverse to pull cool air in from a crawl space and a space heater to raise temps. Have a Nut Brown fermenting now we just ramped up from 65 to 68 degrees to get the yeast to clean up a bit before we keg/bottle. These rooms are both in the basement and insolated so it has been easy to keep temps steady. We made add an A/C unit to one for cold crashing in the warmer months.

Im hoping this will result in more consistant quality beer.

"Fermentation temperature" is always the temperature of the fermenting beer, not ambient temperatures. I've seen a very active fermentation be more than 10 degrees warmer than ambient temperatures, although 5 degrees is more common.

When a yeast strain lists "optimum fermentation" temperatures, that is always the fermentation temperature and not the room temperature. I normally go at the low end of the optimum range listed by the yeast manufacturer, so if the fermentation temperature range is 60-68, I almost always ferment at 60-62.

I almost always ferment my American Ales in a 58-64 F room as well. The actual wort/beer temp. is most likely a few degrees higher during the first 5 days.

Something to think about is if your floors are made of concrete and the ground is actually a good deal colder than the air temp. This can skew fermometer temp readings a bit.

You are on the right track with your thinking. A couple of things I would note:

(1) I wouldn't pay too much attention to the "recipe" temperature; instead focus on the yeast strain being used and the flavour profile you are seeking. Your system/process will evolve to that point if you aren't there already.

(2) Yes, fermentation temperature will be higher than ambient. You have three choices: (a) ignore that fact [this is what lots of people do] (b) ballpark it by going a few degrees cooler on ambient than you want to ferment at (c) check your actual fermentation temperature with a probe or thermometer vs. ambient then adjust future batches accordingly.

I am definately going to monitor my chamber temperature versus the actual beer temperature on future brews.....to get a catalog of data on this for future adjustments....great idea.

Oh yeah....and what about pitching temperature? If I want to ferment at 68F....should I pitch at 65F if I expect temp to rise 3 degrees?? It seems obvious to me that the answer is yes.

Obviously once the initial fermentation is cvomplete....the temp of beer will drop to ambient......when the mild clean-up / fermentation is happening....so at this point is it necessary to increase chamber temp....??

So for example....lets say I want to ferment beer at 68F.....I set my chamber to 65F and lets assume during the first 3-4 days the beer temp is at 68 as planned (3 degrees higher due to yeast activity).......then when the yeast acivity decreases the temp of the beer will start to drop to ambient (i.e. 65F in this case)....at this point would I need to bring temp up in the chamber up to the 68F....or is it fine to let it go at lower temp since 90% or so of fermentation is done anyway....

I realize either way will be ok....but....is there a benefit to keeping the beer temp stable througout the primary.??

Fermentation temperature is, to me, the single most important factor in making good beer. The listed temperature is going to always be the temp of your beer, and Yooper's right- fermentations can EASILY reach 10F warmer than ambient when active- that's bad news for your beer. You need to control fermentation temperatures in a way that you can keep them in the optimal range for the yeast you're using, and avoid changes in temp more than a degree or two.

Does everyone feel comfortable that a carboy 'stick on' thermometer is within 1 or 2 degrees of the worts fermentation temp? How about the temperature reading from a digital controller? I rely on both of these devices to monitor fermentation temperature and not the ambient.

There was much discussion about the accuracy of the fermometer. Some say it's fairly accurate to within a couple degrees, others do not agree. I assume it has a lot to do with how cold your floor is, if the carboy is surrounded by water, or if a cold draft is blowing directly on the carboy.

When I am not using a chest cooler, I just sit my carboy on a wooden floor away from the window. I'm not worried when it registers 58-62 F on the side of my plastic Better Bottles. I took a sample in the past directly from the carboy and the temp. on my very accurate wire digital thermometer read 65-66 F whereas the fermometer was showing the 58-62 F range.

Does everyone feel comfortable that a carboy 'stick on' thermometer is within 1 or 2 degrees of the worts fermentation temp?

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I recently did an experiment on that, using a carboy filled with water. I stuck floating thermometer inside and wrapped a heating pad around the outside. I turned it on and off to get it up and down to various temps over the course of a few days. Using this set up I found that my stick on thermometer consistently read 2 degrees F higher than the floating thermometer.

Regarding pitching temp, I think it's always a good idea to pitch at the low end of where you want to end up, and then bring it up slowly, rather than pitching high and cooling down. If I want to ferment at 65F (like if I'm using WLP007), I'll pitch at around 62F (measured in the wort directly), then put my carboy in the fermentation chamber at around 62F. As the fermentation gets underway it will heat up, and if the stick-on thermometer goes over 65F I'll drop the temp in the fermentation chamber slightly to compensate. That's always worked well for me. I find that in order to keep my carboy at 65F for example, I'll usually need to have the ambient temp at around 60F during the peak fermentation period, and then afterward I'll kick it up a couple of degrees, so that as the yeast settle down the temp stays more or less constant.

On a related note, I've started warming my carboy slightly once the most active part of fermentation is over--usually between 7-10 days after pitching. I find that it helps the yeast finish up more quickly and I haven't noticed any off-flavor production, which I think presents much more of a problem during the really active fermentation period. My current practice is to leave the carboy in the fridge for a week, then move it to a shelf in the basement (ambient temp always about 68F) for the remainder of the fermentation process. By that point the yeast isn't producing much additional heat of its own, so my guess is that the ambient temp and the carboy temp are pretty much the same.

I've found the fermometers to be accurate enough for me, within a degree or two of active fermentation. They always read cool, in my house at least.

I just tested the Fermometer on my one ale pail and it is within +/- 1 degree of my digital thermometer.

The fermometer (different brand) that came with my other (2) ale pails does not even "light up"...(these are older) so I gotta replace that tomorrow when I stop at the LHBS.

Didnt realize they could "wear" out....lol

I have a dual stage controller which controls both the refrigeration in my kegerator/fermentation chamber and a fermwrap heating film. The temperature probe for the controller slides down a stainless Thermowell inserted through carboy cap. Consequently the probe is sitting in the middle of my fermenting beer. The temperature doesn't vary more than one degree.

Steve

Everything I've read and experienced says the stick-on fermometer is pretty accurate. But everyone should "calibrate" theirs so you know how to read it to get an accurate number. For example, when I see yellow on 50f and green on 48f, that tells me the beer is at 48f. I can check with my calibrated lab thermometer and it'll be within a degree.

yso191 said:

I have a dual stage controller which controls both the refrigeration in my kegerator/fermentation chamber and a fermwrap heating film. The temperature probe for the controller slides down a stainless Thermowell inserted through carboy cap. Consequently the probe is sitting in the middle of my fermenting beer. The temperature doesn't vary more than one degree.

Steve

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Thats our next step!

It should definitely be your next step! Temp control is such an important part of beer making. I bought a chest freezer and a Ranco 2-stage controller about a year ago and I couldn't imagine brewing without it.

I heard everyone talking about raising the temp to "clean up" the beer. How long does everyone do this? Do you return to the original ferment temp?

I've been told to ferment @68 degrees....is 65 degrees too cold......as I am brewing ales at this time. Reason I ask, is that I can get a wine chiller cheap, but it only controls temps up to 65 degrees

How long does everyone do this? Do you return to the original ferment temp?

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I usually do it when I need a yeast to perk up and finish out. I probably will raise temp for maybe for a week up into the 68-74 range. I don't usually return it to original temp.

I've been told to ferment @68 degrees....is 65 degrees too cold......as I am brewing ales at this time.

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Actually 65 is just fine for most ales. I keep my fermenter around 64, unless it's something special like a saison or something like that. For beers that aren't supposed to have any esters or yeast derived flavors I ferment at 62-65 depending on the strain. I like that 68-72 range for Belgians and some English beers. Just personal preference I guess.

pelletben said:

I heard everyone talking about raising the temp to "clean up" the beer. How long does everyone do this? Do you return to the original ferment temp?

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My understanding is that The critical time for not letting the fermentation get too high in temperature is during active fermentation - aka when you can see CO2 production. After this the yeast are past the point of producing fusel alcohols and other stuff you don't want. They are wanting to slow down their activity, so ramping the temperature up 1-2 degrees per day rouses them and they clean up diacytel, Acetaldehyde, etc.

SO. What I do is ferment mid range of the recommended range: if that is 60-70, I target 65. Then when all CO2 activity is done, I begin bumping the temp up one degree at a time, morning and evening until I hit 70-71. I leave it there undisturbed for as long as I can. Frequently I have another batch that needs the fermentation chamber, so I keg, then bring the keg into the house (kept at 70* year around) where I keep it for a week or two before cold crashing the beer to 35*.

But I don't even play an expert on TV, so...

Steve

Depends on the yeast strain. I routinely ferment with WLP007 at 65F, or even a degree or two lower. Some yeasts like cooler temps, some like warmer.

PackerfaninSanDiego said:

I've been told to ferment @68 degrees....is 65 degrees too cold......as I am brewing ales at this time. Reason I ask, is that I can get a wine chiller cheap, but it only controls temps up to 65 degrees

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This really depends on both the beer style and the yeast being used. I often look up the optimum range for the yeast and shoot for the low end. I have just built a fermentation chamber and will be looking to control my temperature much more accurately than I could using a swamp cooler.

In most cases the temperature controller on a wine chiller or refrigerator has a much larger temperature range than is desired for fermentation control. Most home brewers using controllers use a probe in a thermowell or taped with some insulation to the vessel to control the wort temperature as much as possible instead of the ambient temperature inside the chiller.

I'm lucky enough to have a closet with a temp range 60-62F. I use A Lux WIN100 thermostat (w/ a modified probe) and a heating pad, it works great, keeps within 1f of the temp

yso191 said:

I have a dual stage controller which controls both the refrigeration in my kegerator/fermentation chamber and a fermwrap heating film. The temperature probe for the controller slides down a stainless Thermowell inserted through carboy cap. Consequently the probe is sitting in the middle of my fermenting beer. The temperature doesn't vary more than one degree.

Steve

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But... stainless is a miserable conductor... Not that it matters... here.

This all comes down to the "average" impact on the experiment. I routinely measure temperature differentials over a few centimeters in columns of various liquids (really cold, mostly). In my case, those differentials matter.

Can I measure a thousand different temperatures inside an active fermentor?

Yes. Absolutely.

Do those differences impact the yeast. Not likely. In fact, the randomness is one reason things move around and nutrients get distributed, etc, etc, etc.

To measure the energy (temperature) of a system, couple the sensor to the UUT (unit under test) and isolate that system....

Stick a sensor in or on the "thing" and insulate it from external power loads (heat).

ie, if you stick it on the outside of a glass container, wrap it with something to keep the convective, conductive and radiative loads off the sensor.

or... stick the sensor into the UUT.

If you want to get serious, remember that an active sensor (temp sense diode, resistor, etc) dissipates some energy (heat) and affects the system temp.

So, really... the question isn't so much about the measurement as to the sensitivity to temperature of the system. At equilibrium, do the yeast care about the (measurable) temp differences as much as we seem to?

Great discussion!!

Cheers

Well some interesting data to add to this discussion:

Yesterday at 5:30PM I pitched my yeast into a Hefeweizen. Actually cooled the wort down further than I wanted to....was targeting 65F for pitch temp (with a 68F fermentation target) but overshot to 62F.......new chiller setup...anyway here is my data:

Fermenter = chest freezer (set-up with heater right now since winter and it is in grage)

Saturday, 5:30PM Fermentation Chamber set @ 67F, Beer Temp = 62F
Sunday, 8:00AM, Fermentation Chamber set@ 65F, Beer temp = 68F
3:00PM, Frmentation Chamber set @ 65F, Beer temp = 69F
6:30PM, Fermentation Chamber set @ 65F, Beer temp = 70F

Also, been checking a lot on chamber temps and they have not dipped below 67F......not even down to the 65F setpoint. SO it looks like the heat created during the process is actually keeping my chamber warm by itself. Maybe a good idea for me to crack the lid to allow some of the heat to escape during first 24-48 hrs in future......of course if it was summertime I would have it in cooling mode.

OR....maybe I need to bump up my sophistication with a dual temp controller......which reads off of the actual beer temp like some others do.

So I really like the idea of controlling my beer temperature directly with a thermowell in the wort/beer.....with a heater wrapped around the carboy which is situated in my freezer.

So....here is what I would need to do.....looking for feedback that this is what makes sense for those of you that do this:

For a typical Ale.....

1) Set my temperature controller (I have an A419 Johnson controller) on my chest freezer for say 55F...so this becomes my controlled ambient temperature.

2) Place freshly brewed wort after pitching yeast.....with fermenter heater wrapped around it... into said freezer with a stopper that has a thermowell going down into beer....and also of course a blow off tube. Insert thermocouple (temp probe from a second controller) into thermowell and set controller to my fermentation temperature....lets say 67F for a mystery ale :cross:.

So what happens then is the "coldness" in the freezer will remove the heat being generated during fermentation.....but if too much is removed the heater will kick in and keep carboy at right temperature.....once fermentation stops the heater will still keep beer at right temp.....

This way I will be controlling the temperature of beer DIRECTLY.

3) In addition...if I buy a third temperature controller, etc....I can place another carboy into fermentation chamber and set temperature as required for that beer even if different than my other beer....

I like this.....costs a little coin to get all of the controls....but who cares.....HOMEBREW JUST IS that important!!!

Does this sound right guys?

Now in the summertime it works too....it works year round actually without having to worry about the true ambient temperature...i.e. outside, basement, garage, etc.....

Do my temperatures seem ok....i.e. the ambient setting in freezer? i.e. if freezer is kept at 55F.,.....will the fermenter heat wraps keep the beer in the mid 60's??

Actually this could work in my basement which in the wintertime is in the low 60's.....just use a fermentor heater wrap with controller...

Thanks!

I'm still pretty low tech, so I don't have a fermentation chamber or even a digital thermometer (mine was giving crazy readings, so I went with what I figured was a more reliable analog model).
Anyway, finally got a tub for a swamp cooler since my last 2 beers tasted like ass. Made a smoked porter last night and overshot my OG quite a bit as I must have underestimated the efficiency of my BIAB method!
Pitched Wyeast 1028. Airlock barely started bubbling by this morning.
I had the ale pail in the tub with the water level in the tub up to the level of the beer in the bucket (2.5 gallon batch, it's actually just barely floating) wrapped a wet towel around it and put a fan on it. Since the apartment is usually sitting between 68-70, I figured the evaporative effect would be enough to cool this beast. Sure enough, when I stuck my thermometer in between the towel and bucket, it read 66.
Came home tonight, thermometer still said 66. Airlock was bubbling quite a bit, so I stuck the thermometer down further to make sure it was between the level of the liquid in the bucket and the towel. Lo and behold, it went up to 72!
I hadn't put ice packs in there earlier as I didn't want to cool it too much, but you can bet there are a couple of ice packs in there now.
Hopefully with it only a few degrees high and catching it halfway through the primary fermentation, I won't have done too much damage.
There's no question that this is why my last 2 beers were bad. I bet they got into the 80s, easily!

Mgortel- why would you set the keezer at 55F only to wrap a heater around the carboy to get it to 67F? Maybe I missed something but that doesn't make any sense to me. Why not just use one thermostat set at 67F?

Mgortel- why would you set the keezer at 55F only to wrap a heater around the carboy to get it to 67F? Maybe I missed something but that doesn't make any sense to me. Why not just use one thermostat set at 67F?

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That is what I read that others do.....and I believe the reason, which does make sense to me, is that if you set the freezer to 67F......during peak fermentation the actual beer will be 5-10 degrees higher than ambient.

SO.....the 55F ambient temp takes away the heat of fermentation....but to make sure it doesnt lower the beer temperature too much the heater cycling on and off keeps the beer at fermentation temp of 68F.....

Once the peak fermentation is over you could just turn off heater wrap and set freezer to 68F for example

ANyone else that does this...can you chime in....to confirm

I think that if you're using a confined temperature regulated chest cooler, you should set it to the desired fermentation temperature. The cooler should keep the wort stable at that temp. give or take a degree.

The rule of thumb that fermentation temp. will always a little higher ambient temp. seems to me, to only be applicable when you are NOT using a temp. regulated chest cooler, i.e. just letting the carboy sit on the floor in your home with fluctuating temps. and air flow.

No, I don't think it's at all typical to use two thermostats running a keezer and a heater both fighting against each other at the same time. Yes it could work, but would waste a lot of energy in addition to requiring you buy another tstat and heater. It's just nonsensical. And it doesn't save any effort since you still have to play with the settings during the course of fermentation.

There are really only two sensible ways to do this: (1) attach your tstat probe to, or inside, your fermenter such that the tstat is measuring the beer temp and cooling the air accordingly, or (2) use the tstat to measure and control the ambient air. Method #1 can result in greater temp swings in your beer, but is more convenient since it is set-it-and-forget-it. Method #2 can give more stable beer temps but requires you to tweak settings during fermentation due to the varying heat generation within the beer.

bobbrews said:

...
The rule of thumb that fermentation temp. will always a little higher ambient temp. seems to me, to only be applicable when you are NOT using a temp. regulated chest cooler, i.e. just letting the carboy sit on the floor in your home with fluctuating temps. and air flow.

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My experience proves otherwise. As long as the beer is creating heat (during peak fermentation) it's essentially impossible for the beer to be at the same temp as ambient. How you control the ambient (I.e. on the floor versus in a fridge) has nothing to do with that. A fan or water bath may decrease the differential, but that has nothing to do with being in a fridge or not.

My experience proves otherwise. As long as the beer is creating heat (during peak fermentation) it's essentially impossible for the beer to be at the same temp as ambient. How you control the ambient (I.e. on the floor versus in a fridge) has nothing to do with that. A fan or water bath may decrease the differential, but that has nothing to do with being in a fridge or not.

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I agree 100%.....if the yeast/beer is generating heat in the bucket the heat has to transfer somewhere.....heat flows from hot to cold....sooooo....the temperature of the wort has to be higher than the ambient by an amount adequate to transfer the heat at a rate equal to the generation by the yeast doing their thing.

If the surroundings are large...i.e. a basement.......the ambient temperature does not change from the heat transferred from the bucket to the basement....so the beer temp rises until the temp difference is enough between beer and basement to transfer heat generation.

BUT....if the surroundings are small, like a freezer or small insulated enclosure....the heat builds up and increases the heat in the AMBIENT air around the bucket (i.e. in the freezer, chamber, fridge, whatever)....so the beer temp has to go even higher.....UNLESS you keep temperature in freezer, fridge, constant by having it cycle on and off to remove heat....

So the beer has to be at a higher temperature than the ambient....as everyone has witnessed I am sure.....at the begginning of yeast activity.....first several days.

mgortel said:

BUT....if the surroundings are small, like a freezer or small insulated enclosure....the heat builds up and increases the heat in the AMBIENT air around the bucket (i.e. in the freezer, chamber, fridge, whatever)....so the beer temp has to go even higher

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Heat does not build up because the temperature control of these types of units are highly regulated. If the sensor notices a rise, it quickly turns on the cooling fan to adjust the temperature back to the stated level.

Heat is created by fermentation, but it's miniscule at about 3-5 degrees. Any changes in the chest cooler temp. via the heat given off by fermentation will be subsequently and very quickly adjusted again by the temp. regulated chest cooler thus balancing everything out at the temp. you originally set. If you're simply fermenting in a closet on a wooden floor, temp. fluctuation is much more erractic and not easily controlled.

Fermenting wort inside a glass or plastic carboy barrier is not exactly a temperature impenetrable surface whereupon the restrictive size of a chest cooler is completely incapable of regulating, if set at the desired fermentation temperature. There's absolutely no need to set it at a lower temperature unless your unit does a piss poor job at temp. regulation.

Exactly....that is why the need to have the chest freezer controlled to a cooler temp than the fermentation temp......

But.....keeping the beer from getting to cold is the trick........thats where the heater and second controller comes in....based on the beer temperature...i.e. temp probe in beer

Otherwise its a guessing game. I think we are on the same page here....

I know I saw a post where some others do it this way and swear by it....

Read the last paragraph again.

If you keep ambient temperature at your desired fermentation temperature.....your fermentation temperature WILL BE HIGHER than the ambient temperature....period. It has to be....otherwise it violates the First Law of Thermodynamics.....period.

In my experience it can be as much as 5-10 degrees F....depends on the beer. Now once active fermentation ends then of course beer will settle at the ambient temperature.

Agree to disagree. I'm not saying that fermentation does not occur without an added heat. But if you have a unit that is fairly precise at regulating temperatures, then the miniscule amount of heat emitted by active fermentation per hour will be re-adjusted by the cooling fan in a matter of seconds, thus negating the effects of any heat driven off via fermentation and balancing the temperature back to what you originally set it at. This is not the case when the fermentor is sitting at ambient room temps. because your home's atmosphere is not nearly as precise at controlling temperature as a chest cooler. That is sort of the whole reason people get chest coolers!