When do you trust your thermometers?

[marmalady]

Just made a batch of strawberry jam, same recipe I've always used, but decided to use my fairly new candy thermometer to bring it up to the temp of 215 the recipe recommends. Usually I just bring the mixture to a boil, and let it go for about 15 minutes, then use the cold plate test to see if it's set.

Well - the thermometer went up past 220 and the jam still wasn't setting, so I just went ahead and did it the way I usually do. Might explain why the fudge I made at Christmas didn't set - was going by the thermometer instead of my eyes!

I also have a Kitchenaid oven thermometer, and have noticed that it runs about 20 degrees off from the oven temp.

So - when you buy a thermometer, how do you trust it to be accurate? And how can you check the accuracy?

[GB]

I test mine by measuring the temp of boiling water and ice water.

[Andy M.]

Originally Posted by GB

I test mine by measuring the temp of boiling water and ice water.

That's what I do as well. I have an analog instant read that I can adjust. My digitals don't provide for an adjustment.

If your candy thermometer isn't registering 212F in boiling water (assuming you're less than 1000 ft above sea level), you'll have to either compensate for that or return it as defective. I vote for returning it.

[Chef Wil]

When I am buying a new one I check it against all the other thermometers on the shelf. I buy the one that reads the average temp. Another thing is I buy only adjustable thermometers and test them in ice water. Ice water will read at 32*F or 0*C at any elevation and, unless it's broke of miscalculated will be right on all through the temperature spectrum through 550*F. Remember, the only place that water boils at 212*F is at sea level, if I tried to set mine in boiling water my thermometer would always be messed up, I live at 3500' elevation and have worked in kitchens a 9,000' where you use boiling water to do the hand washing ;)

[buckytom]

Originally Posted by GB

I test mine by measuring the temp of boiling water and ice water.

i was gonna ask how you test your baby rectal thermometer, but i don't wanna know. i keep picturing you sitting in snow with a pot of boiling water beside you....

[GB]

Originally Posted by buckytom

i was gonna ask how you test your baby rectal thermometer, but i don't wanna know.

I leave that to DW of course

[Michael in FtW]

marmalady - you pose two questions.

For checking the accuracy of a thermometer ... depending on it's scale ... I check it in an ice-water slurry and in boiling water. Since a candy/fry thermometer doesn't normally go down to 32-F - I just check the boiling point of water.

Now, getting jam to gell is another matter - it's a matter of cooking it to the gell stage - not a temperature. Considering the large amount of sugar the boiling point is going to be above 212-F. But, there are other factors involved in gelling than just the temp.

I'm like you .. I cook to the gell stage and confirm it by the "cold plate" method - without a thermometer. A year ago my son and I both got oranges from the same source to make orange marmalade .. he did the temp (using my thermometer that I had tested and knew it was accurate) method and I just cooked it until it gelled. Mine worked without a problem .. he had jars of orange juice.

[marmalady]

LOL, Michael - sometimes the 'old ways' is just better!