Candy Thermometer Accuracy

Homemade candy can be finicky . . . a couple of degrees in one direction or the other can mean the difference between melt in the mouth perfection or a flub you can’t scrape out of the pan- which, incidentally, is exactly how “Fudge” came into existence! Here’s a simple, dirt-cheap tip to check your candy thermometer accuracy to ensure that your candy comes out every time.

Last year a member wrote in to us, completely frustrated because she couldn’t get her candy over 240° no matter what she tried, it turns out that her candy thermometer was bad and she was actually cooking at almost 300°!

How to test Candy Thermometer Accuracy

Bring a saucepan of water to a rolling boil with your candy thermometer clipped to the side. Be sure that the thermometer tip is NOT touching the sides or bottom of the pan, but is fully submerged in water. Water will boil at 212° – but will not get any “hotter”.

Hard water boils at a slightly higher temperature (usually 1 or 2° due to the mineral content)
The use of a tall narrow pot, rather than a saucepan will result in a boiling point of 213°

If your candy thermometer reaches 212° and does not increase, it’s working fine and is safe to use on your favorite candy recipes. If it fails to reach 212° or doesn’t maintain that temperature, you might want to reconsider using it for your candy-making!

Altitude can have an effect on boiling point as well:

Sea Level	212.0 / 100.0
500	211.1 / 99.50
1000	210.2 / 99.01
1500	209.3 / 98.52
2000	208.5 / 98.03
2500	207.6 / 97.54
3000	206.7 / 97.05
3500	205.8 / 96.57
4000	204.9 / 96.08
4500	204.1 / 95.60
5000	203.2 / 95.12
5500	202.4 / 94.64
6000	201.5 / 94.16
6500	200.6 / 93.69
7000	199.8 / 93.21
7500	198.9 / 92.74
8000	198.1 / 92.26
8500	197.2 / 91.79
9000	196.4 / 91.32
9500	195.5 / 90.86
10000	194.7 / 90.39
Source: Boiling Point of Water vs. Altitude, K. Loomis, New Mexico State University Apache Point Observatory