Thursday, June 9, 2011

Brewing with an IR Thermometer

I got lucky, twice (the second time extremely, I thought all hope was lost).  The third time bit me hard, but I was able to salvage it with some quick thinking.  The Easter bunny gave me an Infrared Thermometer (Pyrometer) this year, and I couldn't wait to try it out for brewing.  I wish I would have been a bit smarter.

I jumped into it head first as I usually do with a new toy.  It was high tech, so in my mind it had to be accurate.  The Pilsner that I brewed with it came out perfectly, both original gravity and terminal gravity (this is where I was lucky).  The second beer I brewed with it was my first wedding hefeweisen (now the Hopfen Weiss).  At first, I had just thought the original gravity was extremely low because the flaked wheat I had used turned into a giant ball while brewing.  The fermentation went pretty well, so I ended up with a nice summer, hoppy, low alcohol content wheat beer that would be perfect for the BBQ.  I couldn't complain too much.

The third batch I did was perfect (or so I thought).  I used malted wheat instead of flaked wheat and I hit all of my temperatures right on with the temp gun.  There was only one problem: my original gravity was low, meaning my efficiency was way off just like the Hopfen Weiss.  There had to be something in common with these two batches, and my thoughts started to turn towards my IR Temp Gun.

Naturally, I turned to my engineering background and had to perform some experiments regarding my temperature gun.  Over the course of three brew sessions, I took temperature readings with both my normal thermometer and the gun: at my pre mash water temperature, mash in, mash out, and my sparge water, always aiming for the same target temperature.  Although I cannot say that after my initial discovery that I was shocked by these results, I was surprised that over the temperature span the deviation between the two devices changed.

Red is a normal dial thermometer, and blue is the IR thermometer.

These results confirmed my suspicions, my temperature was consistently off.  When I thought I was reading 158ºF, my temperature was probably up near 185ºF, far above the range of starch conversion.  In a way I am tempted to continue with these tests to build up a better average temperature differential between the two devices so I can use just the IR gun, but all I would need is that one stray time for it to catch me and screw up another of my batches.  No, for now I will continue using my reliable dial thermometers.

Primary: Honey Dunkelweisen
Secondary: Hefeweisen 2 (Honeyweisen), Honey Toasted Oat Brown Ale, Wedding IPA
Total for 2011: 53 Gallons

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