What is the correct method for calibrating bimetallic thermometers?

The correct method for calibrating bimetallic thermometers involves placing the thermometer probe in a mixture of crushed ice and cold water, waiting about 15 seconds to allow the reading to stabilize, and then adjusting the thermometer to read 32°F. This method is based on the principle that the freezing point of water, which is 32°F, provides a reliable reference point for calibration.

Using ice water ensures that the thermometer is accurately set at a common temperature that is easy to achieve and consistently accessible in most environments. This process is critical in ensuring that the thermometer provides accurate temperature readings, which is essential for food safety and proper cooking processes.

The other methods listed would not provide accurate calibration for a bimetallic thermometer. Boiling water can vary based on altitude and atmospheric pressure; it is also less precise than the ice water method. Using a calibration test weight is not applicable to thermometers, and soaking in warm water fails to establish a reliable standard for temperature adjustment. Therefore, calibrating with ice water is the most effective and accurate method.