Red Hot Metal And Water – The Reaction Isn’t What You’d Expect.

There’s a really interesting experiment you can do in the comfort of your own home that demonstrates an effect I’m about to show you. All you need is a frying pan and some water. Heat up the frying pan until its good and hot and then flick droplets of water onto the pan. Curiously the droplets won’t instantly burst into little puffs of steam, instead they’ll skitter around on the surface of the pan in apparent defiance of the blazing surface that’s underneath it. This effect happens when any kind of liquid comes into contact with a surface past a certain¬†temperature but I hadn’t really considered what would happen if you put the surface¬†in the liquid:

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The phenomenon at work here is called the Leidenfrost Effect. It’s a pretty cool reaction whereby an initial layer of vapour formed by a liquid hitting a sufficiently hot surface forms a protective barrier which is what allows those water droplets I described earlier to skitter around rather than turning into steam. It’s clearly visible in the video at the start where a pocket of water vapour forms around the outside of the red hot sphere. It eventually collapses as the vapour isn’t a perfect insulator but it does manage to stay quite hot for a lot longer than you’d expect.

One thing I can’t figure out a good explanation for those is the incredible sounds that are produced. The rapid generation of steam could possibly explain part of it as some of the sounds are similar to what you hear from say a steam wand on a coffee machine but most of them have a definite metallic twang to them. It’s quite possible that all of the noises are coming from the ball itself as it cools down much like some cars which make a distinct “tink” noise when turned off (the noise comes from the exhaust pipe cooling down). I wasn’t able to track down a name or reliable explanation for this effect however so if you’ve got one I’m all ears ;)

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