Using Temp to gauge fermentation

[avibayer]

I have been reading "Froth" by mark denney, and in it he talks about the thermodynamics of yeast. Since energy is released during the breakdown of glucose to ethanol, it makes sense that the temperature of the fermenter should go up a little.

I have three vessels sitting next to each other. A primary and two secondaries. All of them are five gallons, though one of the secondaries is a glass carboy and the other a plastic bucket. The secondaries are at 68*f, and the primary is at 72-74. no bubbles in the airlock, but i attribute that to a ****tty seal.

I conclude that i have active fermentation based on the temp difference. :rockin:

 

[wscott823]

I'd say that's an astute observation brewin brudda. I usually judge my fermentation by three factors: Krausen, fermentation vessel temp, airlock activity.

I purposefully listed them in this order as well. I hear too many stories of homebrewers judging their fermentation solely on airlock activity. Good to see your using your noggin.

 

[maida7]

OK but you'd probably have better tasting beer by getting that temp under control. IMHO 70's is too hot for the first stages of fermentation. I'm assuming this is an ale.

 

[Yooper]

OK but you'd probably have better tasting beer by getting that temp under control. IMHO 70's is too hot for the first stages of fermentation. I'm assuming this is an ale.

Yes, that's what I was going to say. Depending on the yeast strain, over 72 might give you some off-flavors. I like to ferment my ales in the mid to low 60s.

 

[maida7]

Yes, that's what I was going to say. Depending on the yeast strain, over 72 might give you some off-flavors. I like to ferment my ales in the mid to low 60s.

BUT use this info for your future batches. If you go and cool this fermenting batch down to the low 60's it may send your yeast to sleep before the work is done. I'd ride it out at the hot temps for this batch and go cooler with the next one. Besides the off flavors of hot fermentation are produced very early (like in the first day or two) so the damage is already done and cooling now will not help. Lastly, it's a good idea to let your fermentations end warm as this keeps the yeast working when they are getting tired. Ending warm will help the yeast with attenuation and clean up some of the off flavors.

SO for the next batch: Start cool & finish warm

 

[avibayer]

In an ideal world, i have control over my fermenting temps. in my world, i picked the coolest place in my house.

Also, the only off flavors i have gotten so far have been phenols. Suggestions? would fermenting at lower temps help this?

 

[mojotele]

I don't necessarily agree with your conclusion as you're ignoring the heat capacity of the beer. Just because it is hotter right now doesn't mean you have fermentation right now. Fermentation could've stopped and it simply hasn't cooled down yet. I find it takes my batches 12 hours or so to adjust to room temperature.

Now, if the temperature was rising, I'd be more inclined to agree.

EDIT: I'd think you could also get into a situation where the beer was at room temperature but fermentation is still ongoing. Fermentation has simply slowed to the point where the beer is cooling at a rate that is faster than fermentation is heating it.

 

[Yooper]

In an ideal world, i have control over my fermenting temps. in my world, i picked the coolest place in my house.

Also, the only off flavors i have gotten so far have been phenols. Suggestions? would fermenting at lower temps help this?

Probably. Depending on the yeast strain, phenols or esters could be the result of a too-high fermentation temperature. Phenols can also come from chlorine or chloramines in the water supply or from a yeast strain, so temperature may not be the only cause.

You DO have control over your fermenting temps, by the way. It is as easy as picking up the fermenter and putting in a tub of water. Add a frozen water bottle to the water to bring the temperature down. I do that in the summer and can keep a fermentation temperature of 65 in an 80 degree room easily. I float a thermometer in the water bath, to gauge the beer temperature. It's nice because it also insulates the beer, so that even if the temperature starts to rise, it takes the beer a LONG time to catch up to room temperature.

In the winter, it's cold here so I do the same thing in the winter, but put an aquarium heater ($15) in the water to keep the temperature higher than my room temperature of 60 degrees.

Some people find that a "swamp" cooler works well for them. That's just putting the fermenter in a smaller bin with water, and allowing a t-shirt or towel to "wick up" the water over the fermenter. A fan blowing on the set up helps, and this can keep the temperature about 10 degrees cooler than ambient.

 

[maida7]

temp control is probably the best upgrade you can make in your brewing. I use an old fridge that I got second hand used on craigslist for 30.00. I control the fridge with a digital temp controller. The controllers are kinda pricey. The one I have cost me 100.00 but it's worth it. I can dial in any temp and my fermenter will be within 1 degree of what I set it to.

 

[avibayer]

All this is great advice. Things is, i live with my parents at the moment. But, one day i will move out, and i will build myself a sweet set up. Until that day, i'm gonna brew with a bit less control. I dont have a bathtub to spare for my fermenters. Or the space for a fridge. I kinda just stick the buckets under my kitchen table. One day...

I have only been brewing for a year now, and am still just learning about different grain types, hops, ect. But i noticed a difference in temp between the secondary sitting next to the primary. thought it was neat to so how billions of little yeasties can increase five gallons by 4 degrees.

mojotele - you are right that it does not indicate precisely when fermentation has started and stopped, but since i pitched on tues morning, i have been watching it closely, with no action in the airlock. I have noticed the temp rise, so i figured something was happening.

 

[mojotele]

mojotele - you are right that it does not indicate precisely when fermentation has started and stopped, but since i pitched on tues morning, i have been watching it closely, with no action in the airlock. I have noticed the temp rise, so i figured something was happening.

Agreed. I was just being really scientific about it. My only point was that, like bubbles in an airlock, it is not foolproof gauge of fermentation. But, that said, all of us use the airlock to gauge fermentation. We just know not to absolutely rely on it.

In your case, though, I'm sure fermentation is well underway!

 

[mojotele]

All this is great advice. Things is, i live with my parents at the moment. But, one day i will move out, and i will build myself a sweet set up. Until that day, i'm gonna brew with a bit less control. I dont have a bathtub to spare for my fermenters. Or the space for a fridge. I kinda just stick the buckets under my kitchen table. One day...

You don't need a bathtub. Just go to a hardware store and buy a plastic bin. They're pretty cheap. You may need some help carrying the thing to dump it when you're done, that's all.

EDIT: Here's a pic I stole from one of Revvy's posts.