ambient temps for fermentation.... Air vs Water

So I have been making pretty decent beer for the past 8 months now. My big problem has been keeping my fermentation temps consistent. when I have the space i will purchase a fridge for fermenting, but as for now( for the last three beers) I have been doing the swamp cooler with frozen ice bottles.

Now I understand that ambient temps in an open room is going to be different then the temps of the wort because of the exothermic reactions going on, but do you all think that the temp difference is as drastic when the carboy is submerged in water?
example....
If I have a carboy sitting on the floor in a 67 degree room
or
if I have a carboy submerged in 67 degree water

should the temp of the wort be the same in both cases ?

with my flawed thinking, it would seem to me that since water is a much better conducter of temps, that the carboy in the water would have less drastic of a difference in temps.....any thoughts ?

I have a bells two hearted ale clone sitting in the swamp cooler and the water is at 67 degrees, and my fermometer is way out of whack. I used nottingham ale yeast. i'm just hoping it comes out decent

Yep. I'm pretty sure you are correct that the fermentor sitting in the container of water is going to stay closer to the temp o the water than the one in the open air is for the reason you mentioned.

I wouldn't be surprised if somebody on here maybe has done some actual measurements of the wort in a tub of liquid to see how close it tracks .

What do you mean when you say your fermentor is way out of whack?

Zen_Brew said:

Yep. I'm pretty sure you are correct that the fermentor sitting in the container of water is going to stay closer to the temp o the water than the one in the open air is for the reason you mentioned.

I wouldn't be surprised if somebody on here maybe has done some actual measurements of the wort in a tub of liquid to see how close it tracks .

What do you mean when you say your fermentor is way out of whack?

Click to expand...

No, my fermometer. that sticky thermometer that goes on the fermenter. it constanly reads 57 degrees, even when it is completly empty.

Oh OK. My bad on the read. Yeah the stick on fermometers are pretty moody. Pretty much once you get it wet it is toast. I put heavy clear shipping tape over mine and it still went south after a couple months.

becksbolero2 said:

... but do you all think that the temp difference is as drastic when the carboy is submerged in water?
example....
If I have a carboy sitting on the floor in a 67 degree room
or
if I have a carboy submerged in 67 degree water

should the temp of the wort be the same in both cases ?

with my flawed thinking, it would seem to me that since water is a much better conducter of temps, that the carboy in the water would have less drastic of a difference in temps.....any thoughts ?

Click to expand...

I'm really hoping you are right. I had the same thoughts when I set-up my swamp coolers. I couldn't see the temp strips because of the T-Shirts but seems like they will be hosed anyway with the water. I have two Biermuncher brews going, the Tits up IPA and OctoberFast. The Oct uses S-04 which is finicky at higher temps and throws off a apricot like ester.

My water hovers between 64 & 66 which I hope will hold the wort to under 75 but it will be close I think.

I'm fermenting a porter right now that I wanted to keep between 65-70 and my basement temp is generally 70-72. I put the (3 gallon) carboy inside a 6 gallon bucket full of water and put it in a "cold corner" of the basement where the concrete is about 67 because of underground temps, partitioned off with some 2" foam. I use an infrared thermometer, and every time I've checked, the temperature of the water and the wort is about the same - 67° (and, yes, it is fermenting).

HUGE difference... open air is 7*F warmer than ambient, and in a water bath the difference is about 1*F between the water bath and wort temp. I always use a water bath even if I want to ferment at room temp -- just don't add the ice in that case.... Unless I'm making a saison, in which case I let it warm up....

The water will conduct heat much the same as the wort in the fermentor. Whereas air can be more of an insulator. The thermal coefficient of air is much lower than water.

On the other hand, if your fermentor is a glass carboy, glass can be a insulator, but not so much when there is water on both sides of the glass.

I have come to the conclusion that if you have the fermentor sitting in water you can assume the temperature of the bath is the same as the temperature in the fermentation.

I did a more careful test last night, and there is a slight difference in temperature - somewhere about .5-.7° between the water and wort. It may be greater at the height of fermentation, but I can't imagine more than about two degrees, and that would be in the center - the closer you get to the wall of the carboy the less the differential.

When my fermentor is in water I just set my temperature controller 1 degree less than my desired fermentation temperature.

This can be an important point for passive fermentation control. If I had to keep the water temperature in my fermentation bucket 10 degrees below my desired fermentation temperature then I would have to go buy a fridge, which defeats the whole point of my cheapo setup. But if I only need to keep it 1-2 degrees below, then I can realistically use passive cooling.

Bumped, because the thread is worth reading.

I always try to ferment my Blond Ale ~55-60F with Nottingham, but this weekend I was away for about 30+ hours.

Between the yeasties and a 70F degree room, the temperature of the water bath swung from a balmy 55F to 65F. I want the beer to have fewer esters, but I'm sure this will be more than acceptable.

Note that water is only a heatsink!

For example, a carboy in a bucket of water will make the water the same temperature as the carboy, but both the water temp and the carboy temp may be many degrees higher than the ROOM temp. The water in the bucket is heated by the warm yeast action, just as the wort is...the extra thermal mass will just mean that instead of the carboy hovering at 8 degrees higher than ambient, a 5 gal carboy in 10 gal of water may only hover at 2 or 3 degrees higher than ambient, (more water to heat up!)

The swamp cooler works due to evaporative cooling...that is, the water evaporating from the T-Shirt sucks heat out of the carboy....

shortyjacobs said:

Note that water is only a heatsink!

For example, a carboy in a bucket of water will make the water the same temperature as the carboy, but both the water temp and the carboy temp may be many degrees higher than the ROOM temp. The water in the bucket is heated by the warm yeast action, just as the wort is...the extra thermal mass will just mean that instead of the carboy hovering at 8 degrees higher than ambient, a 5 gal carboy in 10 gal of water may only hover at 2 or 3 degrees higher than ambient, (more water to heat up!)

The swamp cooler works due to evaporative cooling...that is, the water evaporating from the T-Shirt sucks heat out of the carboy....

Click to expand...

Very true. It's good to do both the water bath with ice plus the wet t-shirt. That is what I've always done and it works great.

shortyjacobs said:

Note that water is only a heatsink!

Click to expand...

Well, yes. But.

You have also increased the exposed surface area, which is the same principle of the fins used on air cooled engines and radiators, or even just the bumpy surface of a wood stove.

keeping the water agitated helps as well.