Early this morning I brewed a Chocolate Oatmeal Stout. This is the first 12 Gallon batch on 'my' system. I possess a 14.5 gallon conical fermenter, so why not fill it! Since it was a first big batch, it was not without problems and lots of learning. I learned a valuable lesson about combing 24.75lbs of grain along with 8 gallons of water into a 10 gallon mash tun, it worked but just barely. Surprisingly, I achieved 86% efficiency, as compared to my usual 74%. This is fantastic, except the beer is now not within style, oh well. I also learned that multi batch sparging (more than my usual 5 gallon 1 batch sparge - due to the mush tun volume), when you only have 1 burner, means having to lift a very heavy brew kettle onto the burner, something I thought I was finished with after I began using a pump about 6 months ago. Lastly, I discovered something I have been a victim of before, and I thought I had learned my lesson, temperature control.
3 years ago, when I really got into brewing beer, I used two separate digital thermometers. One was a Taylor brand from Walmart, and the other an Oneida brand. I had problems early on with my beer coming out very thin and without body. It turns out the Taylor was completely off at almost any temperature, while the Oneida was off at higher temperatures and the probe had gotten wet. The probes are not designed to have the cable submurged, because the cable/probe junction is not watertight. I had been scratching my head trying to figure out the what why how until I purchased the Cole-Parmer Workhorse Thermocouple.
A side by side comparison in both boiling water and freezing ice water told me what was going on with my digital meat thermometers. I threw the Taylor in the trash, and used waterproof tape to seal up the probe on my Oneida, since it was consistent with the Cole-Parmer.
My beer was instantly better.
Fast-forward a couple years to May of 2012. I purchased my stainless conical fermenter from http://conical-fermenter.com/. The owner is based out of Portland Oregon. I happened to have a class I was attending in Portland, and it all worked out. the conical happens to come with a thermowell and an analog dial type thermometer. I have fermented 10 or more batches of beer in that fermenter, and one of my last batches, a Bohemian Pilsner, has diacetyl . I raised the temperature on my fermentation chamber to perform a diacetyl rest, where the yeast are actually supposed to consume the diacetyl. I also had another, relatively serious fermentation problem with a Baltic Porter back in October. Those two batches in particular don't really make sense because I did everything I know to do. I can control my fermentation temperatures to plus or minus 1 degree using a dual stage temperature controller from Control Products. My temperature probe is placed in the top of the unit. I figured there was enough air circulation with the fermentation chamber's internal fan that temperatures would be relatively consistent throughout.
It had never occured to me to calibrate my fermenter's thermometer, there is a screw on the back for that purpose. Today I used my trustee Cole-Parmer and it said my wort was 64F. My fermenter's thermometer said my wort was 69F, a 5 degree difference. I also have an analog refrigerator thermometer set on top of the fermenter, and it read 64F. I believe, all this time, I have been 5 degrees low on everything I have been making. For some things it may not have played too much of a role, but certainly, it is the reason I have diacetyl in my Pilsner (it's ok if drunk really cold - just like Coors Light), and also is more than likely the contributor to the stuck fermentation of the Baltic Porter.
I had been down this path once before and I have no idea why it never occurred to me to calibrate my thermometer. I calibrate my refractometer every time I use it, so why not my thermometers. I encourage everyone to check out their thermometers. Calibrate, purchase, throw-out, etc all of your brewing temperature gear/devices. It just isn't worth screwing up another batch of beer. I now have high hopes for my Chocolate Oatmeal Stout.
I have found the Cole-Parmer Workhorse is no longer made: