Infrared thermometers have plummeted in price in recent years, and are now inexpensive gadgets for the home cook, not to mention the pros.
What are the primary uses of an infrared thermometer in the kitchen?
Infrared thermometers work very well when measuring the temperature of hot oil. For deep frying it's not a big deal, as standard probe thermometers work fine. But for shallow frying or sauteeing, the IR thermometer does an excellent job at providing the temperature of the oil. (Note that IR thermometers are not accurate when measuring the temperature of a dry steel pan, as the shininess makes the pan look much cooler than it is. IR thermometers work fine on dry cast iron pans, though!)
IR thermometers work rather poorly when measuring the temperature of hot water, however! Rather than measuring the temperature of the water surface, which is usually similar to the mass of the water due to convection, it measures the average temperature of the water vapor coming off the surface! In my experience, boiling water measures about 200 F with an IR thermometer.
One thing I've found surprisingly useful is how accurate it is measuring the temperature of microwaved liquids. This can be handy when bringing milk or water to 100 degrees when making yeast breads. The convection of the liquid when heated by microwave means the surface temperature is within a degree or two of the center of the liquid, at least in my experience.
For hotter liquids, where the water vapor is cooler than the liquid, it may better to measure the side of the pan below the water level.
I bought one to measure the temperature of a firewood oven. Immediately I noticed it was useless.
In order to bake on those ovens, you must have enough temperature in the bricks, not just it their surface. Using the terminology: They have to be soaked. Luckly I had built the oven with plenty of sensors between them.
But there is one dish which needs a lot of temperature in the surface of the oven: pizza. Unluckly my I.R. thermometer could only read up to 325ºC (or so) (600 ºF). That wasn't enough for pizza.
So I bought a new "expensive" I.R. thermometer that reads up to 900ºC (1650 ºF). Now I know greater pizzas are made between 400ºC and 450ºC. (750~850 ºF))
You can't measure the inside temperature. You will just get the superficial temperature which is usually almost useless.
You need a thermometer that can be inserted in the food (for example a meat thermometer) and then you will be able to do exciting things, for example the perfect temperature for frying oil (just under the smoke point) or the steak grade (raw, medium, well done).
As a BBQ master, I use IR thermometers to measure grills for correct temp or find hot/cold spots. However you cannot just read the grill straight down as the IR will read the flame or flame tamers down below. However if you cast your eye at an angle to the grill until you cannot see below and take a reading at that angle, It will read the surface accurately. I also use the IR gun for pressure frying where the oil temp is critical before sealing. (Dont try pressure frying unless you know what you are doing)
To anyone thinking temperature guns are a mere luxury item, they are no more an extravagance than a blender or a food processor. Users are able to cook with confidence knowing that friends and family won’t become ill, refrigerators and freezers are operating at their optimum and foods are cooked perfectly every time. That they have many other uses in and around the family home is just an added benefit. Infrared thermometers are an affordable tool in their own right, but can actually save you money and they will eventually pay for themselves many times over. They may not actually prepare and cook the food for you, but they do take all the guesswork out of the cooking process and will give you more time doing other important things, like eating and breathing.
For more information, see my blog post on infrared thermometers.