What are the two methods used to calibrate thermometers?

The two methods used to calibrate thermometers are the freezing point and boiling point methods. In the freezing point method, the thermometer is placed in a mixture of ice and water, allowing it to read a temperature of 32°F (0°C). This method is reliable because it uses the known freezing point of water, which is a consistent reference.

In the boiling point method, the thermometer is placed in boiling water at sea level, where it should read 212°F (100°C). This method is effective as it utilizes the boiling point of water, which is also reliable, although it can be influenced by altitude and atmospheric pressure. Together, these methods ensure that thermometers are accurately calibrated against known temperature references, which is crucial for maintaining food safety and proper cooking temperatures in a food service environment.

The other choices do not describe standard methods used to calibrate thermometers. The ice point and pressure point methods, standard and calibrated methods, as well as thermal and metallic methods do not correspond to the recognized techniques for thermometer calibration.