# Calibrating Brewing Thermometer

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#### BrewCF

##### Member
I have been calibrating my thermometer by essentially adjusting to 32 degrees in a glass of crushed ice/water. I ran across an column in Brew Your Own magazine that said to basically allow crushed ice to slightly melt in a styofoam cup in the refridgerator. Then, calibrate to 32 deg in the ice/water slush mixture.

I guess my question is, do both method pretty much work the same? What calibration method(s) do most people use?

FYI - my thermometer is a basic dial thermometer that I ordered from Northern Brewer.

#### TheTower

##### Well-Known Member
Either way achieves the same result. An ice/water mixture won't naturally go above 32 until all the ice is melted, or below 32 until all the water is frozen. Hence, a slush is 32 degrees.

#### LeeF

##### Well-Known Member
I don't use digital so I wanted to consider the boiling point also. I boiled water and moved the thermometer from ice bath to boiling to get an idea of not only how fast the thermometer approaches the final temp but how far off the readings were. Good data to have considering all of my thermometers reach a temp then slowly approach the actual temp.
One thermometer read 30F in the ice bath and 214 at boiling. I used interpolation to extract actual temps.

(Actual Temp - 32)/(212-32) = (Temp Read - 30)/(214-30)

or Actual Temp = ((212-32)*(Temp Read - 30)/(214-30))+32

Sometimes I wonder if its worth worrying over considering how hard it is for me to hit and maintain temps anyway.

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