Friday, March 21, 2008

Getting the temperature right

You may remember that I have had some issues with mashing at too low a temperature. Because the beers were mashed too low they were thin bodied as this produced more fermentable sugars. I recently bought a new thermometer (the one on the right), and that helped a little. The recent beers have had more body, but the doppelbock I brewed just before Christmas still was a little thinner than expected. It meant that I still had some problems with the mash temperatures.

Interestingly, I was offered to have my thermometers calibrated at a local brewery using professional calibration equipment. That was exactly what I needed as this would let me know exactly by how much the thermometers were off.

The temperature calibrator system that was used was a Tek Know TC2000 from Scan-Sense. The results from calibrating the two thermometers at 55C, 65C, 70C and 80C can be seen below. Click the thumbnails to see the full-sized photos.

The digital thermometer on the right is clearly the most exact of the two as its readings are the most consistent, but they are still off by 1.5C or so. It was this thermometer that I used for the last few brews, so the dobbelbock was mashed at 67.5C instead of 69C. The old white digital thermometer (now broken) must have been off by at least 3.5C as it read 2C lower than the new one. That is a quite significant difference.

In all this is very useful information to me and it will allow me to hit the mash temperatures much more precisely than before. If you have doubts about the readings from your thermometer then having it calibrated is much recommended. Even small variances on the readings in the mashing range can lead to significant differences in fermentability.

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