Fermentation Temperature Question

[TimothyK]

Hey Folks,
I am fermenting my carboys in a water bath controlled by an aquarium heater and I had a question. I was reading on these forums that the wort temperature inside a fermenting carboy often exceeds that of the ambient room temperature by as much as 10 degrees. However, I would think that the water bath method would control the wort temperature. So if a recipe or pack of yeast calls for a fermentation at a certain temperature, should I set my water bath lower to account for the fermentation heat? Or should I just set it at the temperature it calls for? Hope this makes sense.

Thanks for the help, I need it.
Timothy

 

[harpsbight]

put a thermometer (stick on brew thometer if you have one) on the outside of carboy then adjust temp as needed. after a few you will get an idea of where to start, how to adjust, etc.
hope this helps.

cheers

 

[aiptasia]

I can tell you that yes, as the yeast ferments the beer, there is a rise in temperature in your wort. I have a drop freezer for my fermentation chamber that's controlled by an external temperature controller that can precisely dial in the temperature I need by +/- a half a degree. It has a sensor bulb at the end of a probe wire that I can tape to the outer wall of my fermentation bucket.

 

[freisste]

The beer will be close to the temperature of the water as the water is a great heat sink. When people say that the beer can rise as much as 10* above ambient, they mean if it is not controlled by some other means (like a larger tub of water). Will your beer get above the temp of the water bath? Yes - thermodynamics shows that the heat will not flow out of the beer until there is a difference in the temperature. However, it will not rise much before the heat flows out. I doubt you will get more than about 2* warmer in the beer vs the water bath.

But as was stated, the best bet is to measure both to see how big a discrepancy you get.

Also, controlling temp from the beginning will keep fermentation from getting out of hand. Cooling initially will result in a slower, more controlled fermentation that doesn't produce as much heat as quickly anyway, a cycle that makes it easier to control temp.

 

[TimothyK]

Thanks for the quick responses, and I appreciate all the help. My other question is this: When people specify a certain fermentation temperature, are they referring to the ambient temperature or the wort temperature?

 

[progmac]

Thanks for the quick responses, and I appreciate all the help. My other question is this: When people specify a certain fermentation temperature, are they referring to the ambient temperature or the wort temperature?

the wort temperature. generally, you want the thermometer to read 2 degrees or so below your desired fermentation temperature. the thermometer, in turn, tends to read 2-4 degrees above ambient depending on (1) original gravity of the wort, (2) ambient temperature, and (3) yeast selection.

however, also keep in mind that the temp difference between wort and ambient is reduced when temperature is lower because fermentation slows way down. so if you ferment a beer at 70F, you could very well have center wort at 78F+. at 60F, the center wort might reach 64-66F. down at 50F, the center wort might only be 52F or so.

as you might expect, higher gravity beers cause the more yeast activity and a hotter wort. so if you are doing a barleywine, the diff between wort and room temp will be much higher than if you're doing a basic pale ale.

if you can't control temperature, this is all very academic and you should probably just ferment in a water bath in the coldest spot in your house.

OP - what are your ambient temps?

 

[TimothyK]

progmac, thanks for the info. I never realized that the wort temperature could vary so much during different stages of the fermentation, but that makes lots of sense now.

I am fermenting in my basement which keeps a steady temperature around 60F even during the hottest days of the summer. So I am using an aquarium heater to keep the water bath in the 65F area.

 

[homebrewdad]

however, also keep in mind that the temp difference between wort and ambient is reduced when temperature is lower because fermentation slows way down. so if you ferment a beer at 70F, you could very well have center wort at 78F+. at 60F, the center wort might reach 64-66F. down at 50F, the center wort might only be 52F or so.

I agree with most of what you say, but in a homebrew sized batch - five gallons or so - the difference between the edges and the center are typically not going to be this extreme. In a commercial tank? Sure. From what I've measured, the center wort is only a fraction of a degree warmer in the center in a typical homebrew batch.

 

[progmac]

progmac, thanks for the info. I never realized that the wort temperature could vary so much during different stages of the fermentation, but that makes lots of sense now.

I am fermenting in my basement which keeps a steady temperature around 60F even during the hottest days of the summer. So I am using an aquarium heater to keep the water bath in the 65F area.

you might be pleasantly surprised by the beer that you can make with 60F temperatures. i very rarely ferment above 62F

 

[BigFloyd]

progmac, thanks for the info. I never realized that the wort temperature could vary so much during different stages of the fermentation, but that makes lots of sense now.

I am fermenting in my basement which keeps a steady temperature around 60F even during the hottest days of the summer. So I am using an aquarium heater to keep the water bath in the 65F area.

Since you are fortunate to have a have a basement that keeps a steady 60*F, you don't really have to place the fermenter in a water bath until after 5 days or so. Just monitor it and see what the fermenter temp gets to. A typical ale ferment will do nicely at 60*F ambient during the initial (active) phases, then you'll want to warm it up to 67-68*F to give the yeast some help with cleaning up normal by-products.

 

[TimothyK]

Thanks for the advice. I always assumed 60F ambient temperatures were to low, but I guess not when you consider wort temperatures are higher. I appreciate the great advice.
Timkthy

 

[brewcephus]

then you'll want to warm it up to 67-68*F to give the yeast some help with cleaning up normal by-products.

Thanks BigFloyd. I was looking for some information on this. I brewed up a Pliny clone this weekend and it is the first beer that I have done a temp controlled fermentation on. I built a temp controller with the STC-1000 and have an old fridge that I'm using to ferment in.
Right now the fermometer says we are sitting at 62*. My question is when do you start to raise the temp up? after day 3? day 5?

Again, thanks for the help! I'm wanting to have a really good beer here as I absolutely love Pliny.

 

[BansheeRider]

Thanks BigFloyd. I was looking for some information on this. I brewed up a Pliny clone this weekend and it is the first beer that I have done a temp controlled fermentation on. I built a temp controller with the STC-1000 and have an old fridge that I'm using to ferment in.
Right now the fermometer says we are sitting at 62*. My question is when do you start to raise the temp up? after day 3? day 5?

Again, thanks for the help! I'm wanting to have a really good beer here as I absolutely love Pliny.

If you cool the wort after the boil to about 62 degrees you can just let the temp rise naturally and have no issues.

 

[brewcephus]

If you cool the wort after the boil to about 62 degrees you can just let the temp rise naturally and have no issues.

I think you misunderstood my question. My fermenter is in a temperature controlled refrigerator and is sitting at 62*. How many days into fermentation do you wait before you start raising the temp up to 67-68*?

 

[progmac]

I think you misunderstood my question. My fermenter is in a temperature controlled refrigerator and is sitting at 62*. How many days into fermentation do you wait before you start raising the temp up to 67-68*?

When the krausen starts to fall (or when your hydrometer shows you have reached 75% of expected attenuation)

 

[BansheeRider]

I think you misunderstood my question. My fermenter is in a temperature controlled refrigerator and is sitting at 62*. How many days into fermentation do you wait before you start raising the temp up to 67-68*?

No I just forgot about your beer being temp controlled. I have raised my temp after three days with no issues.

 

[FuzzeWuzze]

I can tell you that yes, as the yeast ferments the beer, there is a rise in temperature in your wort. I have a drop freezer for my fermentation chamber that's controlled by an external temperature controller that can precisely dial in the temperature I need by +/- a half a degree. It has a sensor bulb at the end of a probe wire that I can tape to the outer wall of my fermentation bucket.

If you already have all that why not just put a thermowell in your bucket to get a real measurement?

You can get a thermowell for like 10-15 bucks that are 3/8" od...drill a hole for another stopper, shove the thermowell through the stopper hole(usually 3/8" for air locks) and then shove your probe down the tube.

The innermost wort is always going to be warmer than the outer layer that is in contact with the bucket and cold air.

 

[Smellyglove]

put a thermometer (stick on brew thometer if you have one) on the outside of carboy then adjust temp as needed. after a few you will get an idea of where to start, how to adjust, etc.
hope this helps.

cheers

I'd just like to add that any thermometer on the outside of any carboy should be insulated. Insualted so it doesnt't pick up the temp outside the carboy, but the carboy itself. Or else you'll end up with a reading which tells you what the average temperature between the carboy and the air outside it is.

 

[brewcephus]

Since we are discussing Fermentation temps, is there a downside to fermenting too cold? other than the obvious which would be that the yeast would take forever to get started and finish.

 

[firerat]

Since we are discussing Fermentation temps, is there a downside to fermenting too cold? other than the obvious which would be that the yeast would take forever to get started and finish.

So long as you stay in the yeasts range and don't put them to sleep, then the slow boat is your only downside.

I started slowing down my ferments about 5 batches ago and it really shows.

 

[masterfool101]

Since we are discussing Fermentation temps, is there a downside to fermenting too cold? other than the obvious which would be that the yeast would take forever to get started and finish.

SOME beers work better in the higher ranges of a temperature spread. Particularly strains where you want to see ester production and "fruitiness" in a beer. Think Belgian Ales, or some Hefeweizens . ..

If you're looking for the esters, you'll not want to ferment too cold.

 

[BigFloyd]

So long as you stay in the yeasts range and don't put them to sleep, then the slow boat is your only downside.

I started slowing down my ferments about 5 batches ago and it really shows.

This is generally quite true. There are a few exceptions.

Nottingham is fine down to at least 55*F (that's as cold as I've tried it) even though its published minimum is 57*F. US-05's minimum is 60*F, but some folks report a peachy flavor if you run it below 64*F.

The desire for ester production in certain styles has already been mentioned. That can still involve starting a bit low and ramping the temp up a bit each day to a certain point.