I can’t tell you how many times I have burnt fried chicken or overcooked a caramel and not realized that my candy/deep fry thermometer was to blame. If only I had absorbed enough sixth grade science class to remember how ridiculously easy it is to check to see if had been accurate from the get-go! Simply place your candy/deep fry thermometer in a small pot of water and crank up the heat; the temperature should read 212°F (100°C) as it begins to boil. If yours does not, you can either take into account the few degrees it may run hot or cold when you cook, or return it.
12 comments on checking your thermometer’s accuracy
If you don’t live at sea level, your water won’t boil at 212 degrees F. Ours boils at about 200 degrees F.
I took a food safety class when I worked at Whole Foods and the recommended method for calibrating a thermometer was the freezing method, not the boiling. Water boils at different points based on sea level, but you can always count on freezing at 32 degrees F. Put the thermometer in ice water and calibrate it to 32.
Altitude is a huge factor in boiling point, barometric pressure is as well, to a lesser extent. Here is an excellent boiling point calculator, just get your barometric pressure from a weather website. In Denver, today, our boiling point is 202.754.
do you recommend a particular thermometer? I burned caramel terribly and my boyfriend banned me from making it again until I get a proper thermometer :-) I didn’t see one in your tools and gadgets section so any recommendations would be much appreciated!
Hi Maureen — Not exactly, because I’ve bought even fancy ones and the temps were off. I’d bring one home, keep the receipt, check to see if it’s accurate and if not, return it for a different model.
Jessica’s comment is a good start, but she didn’t go into how to calibrate the thermometer. Most baking thermometers have a nut underneath the head. If the thermometer doesn’t register 32 degree in the frozen water, you can turn the nut with pliers to adjust the needle.
actually, the freezing point also changes above or below sea level, just not as much. And it doesn’t have to be measured just as it begins to boil – all boiling water at sea level is 212 degrees, because as long as it is boiling the heat from the stove is being used to turn water into steam, not to heat the water. (Another way of thinking about it is that the boiling point is as hot as liquid water gets – each molecule of water that gets hotter than the boiling point promptly leaves the pot.)
I think there is some confusion here. A mixture of ice and water (and water vapor because you can’t not have it) will have a temperature of 32°F to enough accuracy for the work you do in your home kitchen. There are rules about the system being adiabatic but even State lab specialists will expect you to “ice point” your thermometers once a year in a reasonably insulated container and take that as 32°f depending on the work you do in your lab.
“So an ice/water bath self-regulates its temperature at 32 F.
The only other quantities affecting this temperature are the air pressure (the bath temperature could shift upward by about 0.003 degrees F during the low pressure of a hurricane) and dissolved chemicals (half an ounce of table salt per liter of bath water will shift the bath temperature downward by about 1 degree F).”
Have you found the perfect candy thermometer yet? I am considering buying one that I can also use for other purposes ( whatever else one can do with a candy thermometer- deep fryer, oven use and other such) if you or any of your readers has a particular model to share please do!
Have no idea which is better- digital sounds like it would be more accurate, but then it needs batteries to be replaced at some point and I’m lazy..
I have 2 digital and 1 pulp and another adjustable; I am always checking these to make sure they don’t get to out of adjustment; I’m a trucker so 1 thermometer just wouldn’t cut it; Try not to drop or bang them. Bit sh*t happens all the time, so having others to double check is about the best way you can make absolutely sure;
Most of the articles that I have read on thermometer testing say pretty much the same thing that you say here. What I am looking for is a way to tell if my deep fry/candy thermometer is correct at 350 deg or thereabouts. I am not looking for extreme accuracy, but I want reasonably close. I am thinking if there is some way to use my oven to heat something hotter than boiling water to measure. I have not figured that out yet but it seems there should be a way. Or, I could check it a 212 and assume it is fairly close at 350. Not quite what I want but maybe the best I can do.
Here’s a down-and-dirty method I use when frying (not so much for candy making, which needs to be precise): I throw a couple of kernels of popcorn in the oil while heating. Popcorn will generally pop at around 350 degrees, give or take, which is perfect for most savory frying purposes. When the kernels pop, I fish them out and proceed with frying.