You Should Test Your Candy Thermometer Before Using It. Here's How

At-home candy making is an exact science, and when working with sugar, precise measurements and a watchful eye are required for the best results. This is especially true when it comes to temperature, as mere degrees of inaccuracy can completely alter your candy's texture. Before making your next confectionary journey into homemade marshmallows or honeycomb toffee, we highly suggest testing the precision of your candy thermometer — a quick, preparatory step that could help prevent future temperature-related mishaps.

To do this, first place your candy thermometer in a small pot or pan, ensuring that the thermometer's bulb is properly submerged. Turn the heat on, bringing the water up to a boil. Allow the water to boil for a couple of minutes. While the water boils — and without taking out the thermometer — check the temperature (If your thermometer isn't digital, always read its temperature at eye level for the highest level of accuracy). It should read exactly 212 degrees Fahrenheit, or 100 degrees Celsius, which is the boiling point of water.

When performing this test, make sure that the bulb of your candy thermometer doesn't touch the bottom of your pot or pan. This is because the metal's temperature will be higher than that of the boiling water, skewing the test's results. To avoid this issue, you can either hold the thermometer in your hand, lifting it up a little, or you can use a candy thermometer with a pot clip for hands-free temperature measurement. 

So your candy thermometer didn't read 212 degrees Fahrenheit after being placed in boiling water — now what? Well for starters, please don't swap it out for a meat thermometer. Since they're designed for completely separate purposes, candy and meat thermometers have several differences that don't make them interchangeable. For one, candy thermometers typically have a greater temperature range. For crunchy sweets like candy apples, this is paramount as the sugar must be brought up to incredibly high temperatures (300 degrees Fahrenheit or higher!) before it reaches that irresistible "hard crack" stage. Also, meat thermometers are typically much shorter than candy thermometers, and since you're dealing with molten sugar, we advise keeping your hands as far away as possible.

While performing the boiling water test, make note of what temperature your thermometer reads. Add or subtract the thermometer's inaccurate temperature with 212 degrees Fahrenheit (or 100 degrees Celsius) to find the temperature differential. If your thermometer reads, say, 220 degrees Fahrenheit in the boiling water, then it displays eight degrees hotter than it should. Therefore, when making candies, let the sugar get eight degrees hotter to account for the difference. Otherwise, you could simply purchase a brand-new candy thermometer. Either way, you should retest your candy thermometer occasionally to ensure its accuracy, especially if you are a frequent candy maker.