Thermometers - Calibration

I have a Blichmann kettle w/thermometer and was wondering how to calibrate it.  I have 2 glass thermometers and one will track with the Blichmann and one is 4 degrees off.  My dilemma is, which one is correct?  If the one on the Blichmann is off I need to fix it but I need to know how to calibrate it correctly.

Check the thermometer in ice water and boiling water. Should read 32* and 212* or less (depending on your altitude).

Thanks Amanda.  In my search I found calibration instructions on Blichmannengineering.com.  I guess I have to dismantle my BrewMometer to do the test.

Boiling test is easy. The ice bath is not accurate unless done correctly. See here:http://www.thermoworks.com/learning/thermapen101_creating_an_icebath.html
Now if we could get a calibrating bath for 150…

I don’t know about you guys, but I don’t mash at either freezing or boiling temps.  I calibrate my brewing thermo at about 150F using a certified lab thermo.

I have a five dollar digital therm that is accurate. Once my mash water is close to temp I double check with the digital. My blickmans were off by five degrees first time I used them. Dead on since

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