A candy or deep frying thermometer is used to measure temperatures of oils (for deep-frying) and hot sugars and caramels (for candy). Instant read or meat thermometers typically measure temperatures up to 220 degrees Fahrenheit (104 degrees Celsius). Candy or deep-frying thermometers measure the much higher temperatures usually associated with these cooking techniques, up to 400 degrees Fahrenheit (204 degrees Celsius).
They have a metal clip used to attach them to the side of a pan, so you don’t have to hold it in place. It keeps your hands and fingers away from hot, bubbling sugars or oils. The temperatures for various stages of sugar cooking are marked on candy thermometers, making it easy to tell when you’ve reached the soft-ball or hard-ball stages.
Most candy or deep-frying thermometers are made of glass, so be careful not to subject them to temperature extremes, which can cause the thermometer to shatter. Clean your thermometer in warm, sudsy water.