Cool Science

Unexpectedly, I learned some chemistry tonite from David Blaine . Is it bad form to give away an illusionist's secrets? Hmmm. Well, I guess I'll risk it seeing as how I don't figure out most of his illusions/tricks any way and it's very interesting science.

The illusion is a great one for Blaine's street magic style; he wanders down the street until he spots some one drinking a hot beverage. That's important. He urges one of the coffee-drinker's friends to produce some coins, a whole bunch. That is also important. He plucks a nickel (interesting choice) from the palm of this unsuspecting person and places it in his own hand. Blaine then pours the other dude's coffee into his own hand onto the coin. Before everyone's eyes the coin melts and slips through Blaine's fingers.

At first, I felt outrage, feeling certain that Blaine had polluted the streets of fair NYC with mercury, lead or both. But I was wrong. I did know he could have only used an alloy with a peculiar property. And after a few moments on the 'net, I knew this could only be Field's metal, a sufficiently non-toxic alloy of bismuth, indium, and tin which has the marvelous property of being a fairly deep eutectic (by 'deep' I just mean that it is a particularly low melting alloy compared to other eutectics). So what is a eutectic alloy? It's a specific mixture of elements which forms a solid well below the melting points of any of the individual components. Of course if any one in my lab were to be caught discarding a few grams of bismuth, tin and indium in the streets I would be fired and my host institution would be fined a six figure sum. Call it 'magic' and apparently the EPA doesn't care anymore. Sigh.

Perhaps the best known eutectic alloy is solder, which epitomizes what a eutectic is all about. Solder is a eutectic metal alloy which melts low enough that we can work with it fairly easily and safely with soldering irons. Another way to look at it is that solder solidifies very quickly once the heat is removed, which is a nice feature since you don't want to risk having the solder deform while you're waiting for it to cool and solidify.

So you have surely figured out now also how this works. Back in his studo, Blaine (or an assistant?) made plaster casts of all of the silver colored coinages and then made a good stash of them all using Field's Metal, which melts at 62 Celsius and therefore is trivial to melt and pour into casts (and is also silvery in appearance). As per the above link, it's so easy to cast Field's Metal that it can be a children's toy! Since Field's Metal melts at 62 Celsius these fake coins will stay solid in Blaine's pocket with no trouble. Blaine urges the bystander to pull out a bunch of change - he needs to spot a good match to the fake coin he has stashed somewhere in his sleeve. When Blaine takes a real coin out of his victim's hand, he only needs a sleight of hand to substitute his own coin. Then pouring hot coffee (a good bet the coffee is hotter than 62 C) onto the fake Field's Metal coin, he lets everybody watch it melt in the palm of his hand and then let's the molten metal slip through his fingers for extra drama.

So 'eutectic' is a pretty scary word, but just recall Blaine's amazing melting coin as an easy mnemonic.