Calibrate at 212 or 32....or toss out??

Purchased a dial thermometer from AHBS. Attempted to calibrate it tonight. Left some ice water out for 15 minutes and placed the thermometer in it. Had to adjust about 5 degrees.

Next, I boiled some water and stuck the thermometer in it. Couldn't get it above 200.

Should I use the ice water calibration, the boiling calibration or should I toss the thermometer.

Thanks.

Ice water or crushed ice with a bit of water? Ice water can be in the mid 30s away from the ice cubes.

Bearcat Brewmeister said:

Ice water or crushed ice with a bit of water? Ice water can be in the mid 30s away from the ice cubes.

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Filled a cup with ice cubes and then added water. Let set for 15 minutes and then put in the thermometer. Lowest I could get was 39?

I have a similar issue and I have started to calibrate at the boiling temp since, since that is closer to the mash temp.

Depends on use: is this probe primarily going to be monitoring mash temps or fermentation temps. For single point calibration, you want to calibrate at a temperature that is closest to the range the thermometer will be used at. Therefore, if this is going to spending most of it's time in a mash tun or HLT, calibrate it at 212F (you can increase accuracy by knowing your current elevation and calculating actual boiling point). If this thermometer is mostly for fermentation temps, go with the following ice bath method:

Vigorous stirring in ice water is key. I used to calibrate temp probes at my last job. Just letting it sit isn't enough. Keep stirring probe around in ice until you can't get the indicated temp to drop any further. Also, make sure you are using as high a ratio of ice as possible: fill container with crushed ice (a large travel thermos is ideal), then top with water. Stick the probe in and stir, stir, stir.

you really need a ton of crushed/shaved ice, and a little water.

also, unless you live at sea level, water will boil below 212F

I believe at my elevation its like 210.6F

Get the current barometric pressure from the Weather Channel, and use a calculator to figure the boiling point. [ame="http://www.google.com/search?hl=en&q=29.92+inches+in+mm&btnG=Google+Search"]Use Google to convert inches of Hg to mm[/ame]. You can calibrate at ~172°F if you heat high-proof liquor slowly, to the point where the alcohol is evaporating off.