by An important part of candy making is cooking it to the correct temperature. The boiling point of water varies depending on altitude or variations in barometric pressure. Dropping or rough handling can also cause a shift. This can be compensated for by finding your boiling point and adjusting your recipe accordingly.
To do this:
1. Immerse the thermometer in boiling water.
2. Water normally boils at 212 degrees F. Therefore, subtract your reading from 212, and that is how much you need to deduct from your recipe temperature. For example: I live at a very high altitude (Colorado- 6,000 feet above sea level); my water boiled at 202 degree F instead of 212… so I subtracted 10 degrees from my recipe. My candy recipe indicated to boil to 300 degrees F, so I only boiled mine to 290 degrees F.
