: How to measure the temperature of a pan? When I need to know if a pan is above or below 100 Celsius but don't have a thermometer handy, I squirt some water on it. Say I want to check for another temperature, e.g. for the

You can get a remote-sensing thermometer (they have a laser that shines on the object to show you where you're pointing it). They read reasonably accurately without touching the heated object, and come in various sensitivities. Mine reads as high as 700 degrees F, but there are cheaper ones that don't go as high.

Apart from that, I would think you'll always be just estimating and not very accurately at that.

Don't forget also that the temperature of your cooking surface must be higher than strictly required for the Maillard reaction. If the meat needs to get to 155C for it to occur, you will probably need to heat your pan higher to account for heat lost to the meat on contact.

And for killing bacteria, you may also need to get the entire piece of food to the required temp, so a regular food thermometer is a better bet than trying to measure the heat of the pan.

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Here's one example: The Rouxbe cooking school has a video lesson demonstrating how to check that a pan is at the right temperature for pan frying to prevent the food from sticking to the pan. Their method is to make use of the Leidenfrost effect. The effect is that as the pan heats up, at some point a drop of water put into the pan no longer immediately evaporates, but forms a ball that glides on the surface of the pan. The video is also available on YouTube:

This may be reliable enough for the intended goal of preventing the food from sticking to the pan, but I'm not sure whether this indicates a very specific temperature, as it says on Wikipedia:

The temperature at which the Leidenfrost effect begins to occur is not easy to predict. Even if the volume of the drop of liquid stays the same, the Leidenfrost point may be quite different, with a complicated dependence on the properties of the surface, as well as any impurities in the liquid. Some research has been conducted into a theoretical model of the system, but it is quite complicated. As a very rough estimate, the Leidenfrost point for a drop of water on a frying pan might occur at 190 °C (374 °F).

It certainly looks cool though.

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Sauté / stir fry : When you're just below the smoke point of an oil, it'll shimmer ... but that's only useful for a precise temperature if you know what the smoke point for that oil is, and you actually want to use oil for cooking.
Grilling : I can't remember if it was an episode of Good Eats or on Alton Brown's first book that he recommended that if you had an automatic ice maker, so had consistent sized ice cubes, that you time how long it takes them to melt at different temperatures, so you could use that to judge how hot a grill is.
Grilling / Pans in general : For grilling, and campfire cooking, I've always gone with the hand near the cooking surface to gauge how hot it is, but I don't know that it's all that accurate ... and people have a different tolerance for pain, so you'd have to do some tests to calibrate. It doesn't work as well for cooking on a stove except for cast iron; I suspect it requires a more radiant heat source.
Deep / shallow frying : I like the wooden spoon test -- dip something wooden into the hot oil, and as there's moisture in the wood, you should see small bubbles rapidly form if it's hot enough.
Searing : Listen as you add food ... After you've added a bit of oil, touch the food to the pan, and you should hear sizzling. If it doesn't, pull it back and wait a few more minutes for it to heat.
Breadmaking : If I need warm water for making bread, I'll run the hot tap against the inside of my wrist ... once it feels slightly warm, but not hot, it's just above body temperature, so should be good (around 38-40°C / 100-105°F)

None of these are going to be completely precise, but there's lots of ways to gauge temperature other than a thermometer.

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