How much can evaporative cooling change the fermentation temp?

[coneal]

Has anyone used the "T-shirt in water" method to reduce their fermentation temps? How much does it lower the temperature?

I understand that the temperature change is a function of the evaporation rate, which depends on multiple factors (air temp, relative humidity, science, etc...). I'm happy to get really into the weeds on this, but first I'd like to hear someone say, "I do this and it lowers my ferm temps by 82 degrees. Celsius." Or however much it actually lowers the temps.

I ferment in an unfinished / unconditioned part of my finished basement. I'm in St. Louis, MO and summers here get hot and humid. My basement gets into the upper 70s, so I'm looking for ways to drop a few degrees without spending much money. Thoughts?

 

[billl]

Definitely not 82!. More in the 5-10F range. But as you pointed out, it depends on all sorts of factors.

Anyway, it's essentially free to try, so fill up a carboy with some water and turn on the fan.

 

[ChelisHubby]

I was able to get 3 degrees without using ice.

 

[flars]

I have gotten an 8°F drop with a wet towel and fan. The carboy was in a tray of water 7 inches deep. Ambient temperature was 68°F. The beer was OG 1.064.

Leave your thermometer strip uncovered and not in the air current of the fan. The thermometer strip will be cooled more than the wort.

 

[jbsg02]

Setting it in a large volume of water, like in a bethtub, can keep the temperature swings to a minimum even if it doesn't lower the temp by much

 

[Onkel_Udo]

In OK with relative humidity in the 60% range, 5 gallon carboy in a tub of water about 6" deep, t-shirt and a small fan I would see my wort temps stay about 68 f when the house was at 70 f during the height of fermentation's exothermic activity. Before I used this method, 72-73 f was normal for the same time period.

Once the activity slows down it tends to be about 66 f.

 

[lowtones84]

As others have mentioned, get a fan on it too. When I first started using a swamp cooler and this method, I accidentally got my wort down to the low 50's with frozen water bottles in the swamp cooler, a wet shirt covering the bucket, and a fan on it. I guess I could brew a lager

 

[giraffe]

4-5 degrees F. But I live in Portland where the humidity is often very high 9 months of the year.

 

[Psylocide]

I wrap a wet towel around mine and it'll drop the temp ~2°, which is more 2° than the 4° I get from just setting it on the cement floor in my utility room.

Those two things together help me keep my ales in the 65° range for the initial "hottest" fermentation period, and 62° when initial fermentation has slowed down.

At that point, I usually pick it up off the floor and wrap it in a dry towel to keep the light out.