Calibrating Your Instant-Read Thermometer

Forgotten in the back of a kitchen drawer rolling around with an odd number of corn cob handles and a tiny wooden mustard spoon. Surfacing once maybe twice a year to check the Thanksgiving turkey and the holiday prime rib roast. Maybe you have just purchased one or use one all the time yet get unsatisfactory results. How do you know if it is accurate? How do you check it?

Calibrate

Calibrating your instant-read thermometer is a chore that is easy to do and should be done regularly if you use one often or before each occasional use. Your thermometer should also be checked for accuracy if you have dropped it or are using a brand new one for the first time.

To calibrate an instant read thermometer you have two options; boiling water or ice water. Water at a rolling boil and ice water (water generously packed with ice) both hold an accurate temperature; 212 degrees Fahrenheit is the temperature of boiling water and 32 degrees Fahrenheit is ice water. The only real difference of either one is which you would prefer to hold your hand over for a minute or two while checking your thermometer. Ice water it is.

Notice how the face on the left displays
a specific mark for 32 degrees. I prefer
this for my thermometers.

Purchasing a thermometer that has a
wrench built into the sheath
is your best bet.

Method

• Grab a drinking glass deep enough to accommodate the majority of the stem of the thermometer yet not so large that the face will drop in and be submerged in the ice water.
• Fill the glass with ice, tightly packing the ice so there is as little vacant space as possible.
• Fill the glass of ice with very cold water and let stand for 4 to 5 minutes.

• Remove the sheath from your thermometer and insert the stem into the ice water making sure the majority of the thermometer's stem is submerged and surrounded by at least an inch of the ice water. 
• Allow your thermometer to sit in the water for at least 30 seconds or until the needle stops moving. 

Note: Don't rush this step. As your thermometer's needle gets close to it's temperature point it will slow down and move slightly. Make sure the needle has rested on a particular temperature mark for a few seconds before considering your calibration finished.

• Hopefully your thermometer reads 32 degrees Fahrenheit. If it does not then you will need to correct the thermometers reading by gently turning the nut located where the stem of the thermometer meets the head or face.
• Keeping the stem of your thermometer in the ice water use the built-in recalibration wrench which can be found on some thermometer sheaths or use a pair of pliers to move the needle to read 32 degrees. 

Note: You may need to drain out some water and add more ice to ensure that the water is of correct temperature while you making these adjustments.

• After adjusting the needle, rest the thermometer in the ice water for a minute to make sure it is reading the correct temperature.

I only use Instant-Read thermometers because they are a better fit for my style of work and work environment. In a professional kitchen or while catering on-site tools can be lost, borrowed and not returned or damaged and just abused due to their frequent use. Instant-Reads are cheap, very accurate and to some degree can be considered "disposable" when compared to a pricey digital thermometer.

Digital thermometers are great if you are able to control their use and environment. Dropping them, exposure to heat & moisture and the chance that one slips into a liquid while you are using it are all detrimental accidents to a digital tool. If you work alone or with people you can trust and have a relatively organized kitchen then investing in a digital thermometer is a great idea.

For more information on calibrating an Instant-Read or digital thermometer I have listed a couple reputable links below.

Dial or Instant-Read and Digital Thermometer Calibrating

Department of Agriculture & Consumer Services

National Restaurant Association