(Semi) Live Temperature Data for Batch #23 Fermentation

I'm inputting this data in to a spreadsheet by hand and this chart will auto update to reflect the data. (Note: All done.)

I can't get it to size correctly and legend is cut off. The orange line is the fridge thermostat setting. Fixed.

As you can see, I had to babysit things for a bit around hour 27. To elaborate, the wort temp hit and stayed at 71F (max for this recipe is 72F) despite small ambient adjustments. I finally cranked down the thermostat and let the fridge cool. After about 10 minutes of cooling, the fridge hit 50F and the Wort dropped to 70. At that point I returned ambient to 63 and things stabilized.

UPDATE: Around hour 40 I have started to bring the ambient up as the wort has dropped to 68F - the lower limit of our acceptable range for this recipe. I want to bring the wort back up to 69F or 70F and hold it there for the rest of the fermentation.

UPDATE: As of hour 60-whatever, the wort has stabilized to ambient temp. As the interesting part seems to be over, I will no longer be updating the data set. This was a very interesting experiment and I think we collected some valuable data. We'll be doing this for the next several batches to see how they vary and to see if we can anticipate our ambient temperature adjustments.

Watching the Wort Temps

Now that our Coke fridge has been modified to control the temperature, we need to learn how to use it. As wort is fermenting in to beer, the yeast actually produce heat. I have read various estimate as to how much this will heat up the wort (4 -10 degrees F), but we need to find out definitively. Yeast produce different flavors depending on the temperature of their environment (the wort) so controlling that temperature is our goal.

Using a wireless thermometer, we installed the probe (long probe is looooong) in the lid of one of the primary buckets. This will let us keep a close eye on what is happening inside as fermentation takes place.

For this recipe (the Belgian White) we want to keep the wort between 68F and 72F. As the temperature inside the bucket tries to climb, I will counter it by dropping the temperature inside the Coke fridge.

Eventually we would like to make this automatic by wiring the probe directly to the thermostat, but for now it will be hands on.

As of this morning (16 hours after we pitched our yeast) the wort temp is 2 degrees warmer (69F) than the ambient air in the fridge. Fermentation is going great-guns, so I'll be checking it every hour or so and gathering data.

Fermentation Temperature Control

Controlling the temperature of fermenting beer is key. Remember my swamp cooler? We're not going to need that anymore...

Stay Cool

I discovered a thread on homebrewtalk.com asking members which techniques/equipment/knowledge had yielded the biggest improvement in their beer. Almost without exception, the answers included fermentation temperature control.

Each yeast strain has an operating range. Trying to ferment outside that range can lead to stuck/incomplete fermentation and/or the development of sharp tasting fusel alcohols. Even the top and bottom of the operating range can yield different flavors from the yeast.

Yesterday, I took a hydrometer sample from on of my batches and was not-so-amazed to find the temperature of the sample to be 75 degrees - outside normal operating range for my yeast which is 60 - 72 degrees. It has been hot here and the basement is slowly warming up as we have no climate control at all down there. It gets some ambient cooling from the AC units upstairs, but not much.

So here is my low no-budget cooling set up: A tray of water with a frozen 2 liter in it, old T-shirts over the primaries, and a fan. The water wicks up the T-shirts (just starting in the picture) and the fan helps speed evaporation hopefully cooling the air around the buckets. The frozen 2 liter lasts about 24 hours, and then gets swapped for a fresh one. There is also a dash of Star San in the tray of water to make sure it stays clean.

I checked the temperature this morning. I did not put a frozen 2 liter in yesterday as they were still freezing , but the temperature of the beer had already dropped 3 degrees. I added the now frozen 2 liter this morning, so we'll see how it is tomorrow.

At some point I would like to get a nice big chest freezer so I can keep fermentation temps right where I want them, but until then I'm hoping this set up will at least let me keep the temps within the acceptable range.

EDIT: 24 hours later, the beer is down to 68 degrees. Awesome!