Accurate oven thermometers
The old saw is that you should always check your oven temperature with an oven thermometer because oven settings themselves are very inaccurate. This is true, but if you buy an oven thermometer, how do you know it’s accurate either?
I went out and bought a very cheap (£10) oven thermometer. This one uses a bi-metalic strip and so it works the same way as the thermostat in the oven itself.
It’s not too accurate either.
If you take the reading on the oven thermometer and the oven’s own dial, they agree to within 10-15°C, at least between 60 and 140°C where I did my testing. Unfortunately when I added a small glass of water to an oven which was supposedly at 130140°C and left it there for 30 minutes, the water didn’t do very much. So either I have found some magical water which can be super-heated, or else both my oven and my oven thermometer are wildly inaccurate.
This is not just theoretical. I was hoping to cook a chicken tomorrow for 4½ hours at 60°C to obtain a succulent “perfect chicken”, but that’s not too clever if all my guests get food poisoning. (Chicken has to be raised to 60°C for 15 minutes or so to guarantee to kill nasties like salmonella. If the temperature is less than that, the salmonella have a little party).
Companies which sell oven thermometers compete, it seems, on two things: price and the supposed range of temperatures (eg. “our oven thermometer costs just £4 and covers 50-350°C!). Great. Well no, not great. I want to know how accurate the thermometer is, and that doesn’t just mean that it tells me the temperature is 123.45, but that it really is. The nearest degree would be fine — I don’t need to know about the point-four-five.
I don’t really have an answer to this. Is this £80 digital thermometer worth 80 quid? Perhaps I should spend £60 instead. Or is £15 enough?
How do I tell?
Edit
That photo is for real, no GIMP, really!