Why is it that if we wet our fingers before putting out a candle, we don’t get burned, but if we grab a hot pan out of the oven with a wet oven mitt, we get burned?

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Why is it that if we wet our fingers before putting out a candle, we don’t get burned, but if we grab a hot pan out of the oven with a wet oven mitt, we get burned?

In: Physics

A thin layer of water can *very* briefly protect you from hot temperatures by absorbing the energy and evaporating before the heat transfer reaches your skin. For an object with very little residual heat like a candle wick, this is sufficient.

A much more massive metal pan has vastly more heat to give, and the large volume of water only serves to conduct it to your hands more efficiently.

When you use a wet towel to get something out of the oven, grabbing the pan creates steam that burns your hand. The same goes for the oven mitt.

Even if they were the same temperature to start with, there’s very little hot matter in a candle flame compared to the hot pan. The total amount of energy in a candle flame at any given time is quite low, and the water on your fingers is sufficient to absorb the heat by the time the flame goes out. In contrast, a pan hot out of the oven holds significantly more heat, enough to heat the water in the mitt to sufficient temperature to burn you.

It’s a matter of surface area and water being a great conductor of heat.

A candle is very hot but only a small point at the end of the wick is actually burning. if you snuff it out with wet fingers, that tiny point of heat is distributed across the much greater surface area that is your fingers squished together and you barely feel it.

A pan is large and thus contains *vastly* more actual heat energy. The metal of the oven mitt is a great conductor, as is water in a wet oven mitt. All of the heat from the pan is conducted almost instantly through the water and into your hand. The surface area ratio of “hot thing : hand” is much greater with a pan than it is with a candle, and all the heat from the pan doesn’t “go out” instantly like it does with a candle. It just keeps pumping heat in until the temperature of the pan and your hand are the same.

It takes much longer for the mass of the pan to cool down. The candle flame goes out and the tiny wick is cooled off almost immediately.

Heat v. temperature, and amount of contact time

the candle has a lot of heat but very little thermal energy and you snuff out the reaction instantly. The pan has lots of stored heat and you’re in contact for a longer time. More or less.

As others have pointed out, the tip of a burning wick doesn’t contain very much energy. A hot metal pan is insanely energetic by comparison. In either case, you need enough water so that it’s not instantly converted to steam.

[https://www.youtube.com/watch?v=yTOCAd2QhGg](https://www.youtube.com/watch?v=yTOCAd2QhGg)

Mythbusters did it first.

the candle side seems to have been covered pretty well at least. As for the oven mitt, think of snowboarders. Most of them, rather than wear one big puffy coat, will wear multiple layers of thinner material. That’s because the trapped air between layers is itself actually a really good insulator, meaning it takes a while to change temperature, so it’s a good material to keep a hot space hot, or a cold space cold.

Actually, they tried to use this principle for houses too, by making air filled walls sealed in plastic sheets. It worked great for temperature, but eventually some really toxic mold grew in the air pockets, so it didn’t take off.

But yeah, your hot pad is made (usually) of something with air trapped in it. Because it takes so long for that trapped air to get warmer, you have time to do what you’re doing with the really hot thing, then put it back down before a dangerous amount of heat reaches your hand. But the water is a much better conductor… it gets hot or cold really fast and then spreads that temperature on to the next thing. So if you’re out in the snow and sweat through your wool jacket, now you’re also in tons of danger because your body heat gets out through the damp stuff way way faster than before. Same concept with the oven mitt getting wet, and transferring heat.

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This is two different things: thermal mass and conductivity.

The moisture you give your fingers to put out the candle provides them with enough thermal mass to absorb the energy from the candle, without dramatically changing the temperature of the water (the water can absorb a lot of energy without changing temperature) Also the water is a better conductor than your skin, so it spreads the energy across the liquid much better.

When you wet an oven mitt, you turn what should be insulating you from the heat into a better conductor, and the heat travels through the water in the glove to burn your hand.

I learned a similar lesson after bringing socks to the beach to help walk across the hot sand. I went back to our house at one point and thought it would be “really smart” if I dipped the socks in the cool pool water before heading back on the burning sand to our site. Big mistake.

You don’t even need to wet your finger to put out a candle. I never did and it barely feels warm.

Warmth and temperature are not the same thing.

A candle might be a few hundred degrees, but it doesn’t radiate (much) thermal energy. The wet on your hand will be enough to quell that intense – but small- energy source.

But the hot pan, despite having a lower temperature, is larger, and had more thermal energy in its metal/Pyrex structure. That abundance of heat is enough to shluck through a wet mitt through conduction. The heat from the over pan cannot be quelled by a soggy mitt, so instead that thermal energy agitates the water, making it hot, and soon enough the heat conducts through.

A good mental thought experiment that could help with understanding is to ask “How much volume of water will it take to cool down this hot object?” Framing a question like that makes you begin to consider the energy content of the hot object, not necessarily its temperature.

In fact, it is known that the temperature at the hottest part of a candle’s flame can be up to 2,500 °F, yet the flame could be put out by a single drop of water. Hence a wet finger is protected when touching a candle flame. But you can imagine that a hot pan out of the oven will be barely affected by a drop of water. The hot pan has tremendously more energy content than a flaming candle.

So THAT is why I burned my hand 5 minutes ago making pizza. The glove was wet. I didn’t know you get burnt that way. Thanks

Oh dude. I was drunk and stoned a few weekends ago and grabbed a red hot cast iron pan with my bare fucking hand. The skin is still peeling off

If you take an iron pan out of the oven and throw water on it, it will immediately will turn to steam. FWOSSH! The same thing happens when you put a damp mitt on it. The water in contact with the metal will turn to steam very quickly and hit your fingers super hot. It depends on the ratio of the metal type, how hot it is and how much water the mitt is holding. If you have a lot of water and low heat, you are fine as the water can take it without turning too hot or even flash into steam. But if you have lots of heat and low water, the water will be “overwhelmed” and burn you.

Because the heat stored energy in the pan is magnitudes greater than that in a candle, and the conductivity of metal is vastly greater than a wick.

This dude wants to know why you can’t just blow out a bonfire but you can a birthday candle