AROUND 40 years ago, at Hull Fair in England, I saw a man dip his fingers in molten lead. He also poured it into his palm and ran it through his fingers. He seemed to suffer no harm although it was real lead; I found a solidified splash and checked. In my vacations I used to work for one of the showmen at the fair, so I found my boss. “That fellow with the molten lead, why doesn’t he burn his hands?”
“Jarge the gypsy? He gets burnt all the time but that’s because he is usually drunk. It doesn’t really hurt, would you like to try? You can have his pitch. Buy him a bottle of whisky and you can have his take for the night. I’ll come with you and talk to him.”
I was not going to be rushed into this. Have you tried it? How is it done? “Yes. Your hands must be very clean with short nails and no cuts. The molten lead must be very hot. If it is not hot enough it freezes round you fingers and burns them off.”
“But that fellow’s hands are filthy!”
“That’s one reason he keeps burning them!” Over the years I worked on a number of sideshow stalls but never had the courage to try the molten lead act. It intrigued me and I wanted to know more. My boss believed in magic. He believed that with enough faith the human body could work miracles and this was sufficient explanation. It seemed to me there ought to be an alternative rational explanation but none presented itself for many years.
Then in August 1977, Scientific American had an article by Jearl Walker who ran the regular “Amateur Scientist” column. This was a watershed article. It dealt with drops of water on hot metal, fire walking and molten lead. Walker built a pit and tried firewalking for himself.
Firewalking was known from Asia and the South Pacific but Walker seems to have been the American pioneer. Apparently he had never seen it done, not even on film, but his experiments convinced him it was possible. The American craze, which became a new-age cult (and a rip-off) eventually reaching New Zealand, started there.
Walker used the Leidenfrost effect to explain all these apparent miracles. J.G. Leidenfrost had published in 1756, but his work appeared in English only in 1965 so it was new to many people. Walker describes a beautiful series of experiments in which he placed drops of liquid on hot metal and timed how long they took to evaporate. He found that for distilled water, if the metal was below 210o C the drop lasted about 10 seconds. If the plate was above 240o C the drop lasted about 65 seconds. This is basically what Leidenfrost had found 200 years earlier.
But this seems crazy because the hotter metal takes longer to evaporate the water. The explanation is that liquid and metal are not quite in contact at high temperatures. A layer of vapour separates them. Convection currents do not form to distribute the heat within the liquid so it stays cool except at the surface where rapid evaporation occurs, so constantly renewing the insulating vapour layer. However Leidenfrost did not produce this theory, which is modern, he simply investigated the phenomenon.
It seems Walker was wrong to use this argument to explain firewalking, there is an adequate explanation which does not invoke the Leidenfrost effect. This has led to the effect being dismissed as unreal — that it is just a fancy term to confuse the gullible.
But wait a minute, if we can touch hot metal, that effect cannot be explained away by saying that metal has a low thermal capacity and is a poor conductor of heat. Such an explanation is fine for glowing charcoal, but not metal.
Jearl Walker also tried dipping his fingers into molten lead at a temperature between 400-500o (C. But he had to wet his fingers first; with a dry finger he could only briefly touch the surface. So how did Jarge the gypsy manage? Well, his lead was presumably hotter. Ideally it should be nearly boiling, about 1700oC!
Walker seems to have been unaware that Lyon Playfair, professor of chemistry at Edinburgh University last century, used to give an annual public lecture which included the molten lead demonstration. He would wash his hands in ammonia to remove grease, then dip his hand in the molten metal and ladle it out in his palm. Clearly, longer contact can be made when the metal is very hot. The laboratory technicians at Edinburgh remembered the tradition and the demonstration was performed at irregular intervals in the first half of this century. I have a very poor copy of a photo taken in 1938. James Kendall, then professor of chemistry at Edinburgh is in charge. Molten lead near its boiling point is being poured from a cauldron which had been heated in an electric furnace. The professor’s daughter, Jean, is passing her hand through the stream of liquid metal.
The account does not say if the demonstrators used wet hands. My recollection of Jarge the gypsy is that his hands were dry, but at this distance memory can play tricks. Anyway, firewalking is ho-hum these days. How about someone organising a molten lead demonstration for the next Skeptics Conference?