If you live at a high altitude, chances are, you're familiar with some changes you need to make when baking breads and cakes. The difference in air pressure at higher altitudes means that baking times, temperatures, and sometimes even ingredient ratios need to be tweaked to get the best outcome. But did you know you might also need to make adjustments in your candy making to compensate for high altitudes?
If you are at a high altitude and do NOT make any changes to your candy recipes or procedures, you will most likely end up with overcooked candy. This is because water boils at lower temperatures at higher altitudes, so you do not need to cook your candy as long, or to as high a temperature, as you would at sea level.
So what adjustments are necessary for high altitude candy making? Good news! It's actually a really easy fix thing to figure out. It will be different depending on your actual altitude, so the easiest and most reliable way to figure out what temperature conversions you need to make is to perform the boiling water test with your candy thermometer, as described on this page.This is the best way, because not only will it account for your altitude, but it will also take into account any irregularities or inaccuracies with your specific candy thermometer.
However, if you do not have time to test your thermometer in boiling water, or if you just want a general idea of how to adjust candy temperature recipes, here is a handy rule of thumb:
Subtract two degrees Fahrenheit from a stated temperature for every 1000 feet you are above sea level.
For instance, if you live at 2000 feet above sea level, your approximate conversion would be four degrees less than the stated candy temperature. So if you were making a recipe that called for the candy to be brought to 240 F, you would only boil it to 236 F.
Another example: if you live at 6500 feet above sea level, your conversion factor would be 13 degrees less. (2 x 6 (thousand feet) + 1 degree for that extra 500 feet.) If your recipe called for 280 F, you would only cook your candy to 267 F. As you can see, the higher the altitude, the more important it is to do this conversion. Even a few degrees can make a huge difference in the successful outcome of the candy.
Remember, this is just an approximation, and for a more accurate conversion formula, you should do the boiling water test on a regular basis.