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How To Dip Your Fingers in Molten Lead, and Other Useful Tips

Retired Article • Written by Alan Bellows

David Willey, a physics instructor at the University of Pittsburgh, has written an article explaining the physics behind four dramatic presentations that he demonstrates for his physics classes: walking on a bed of broken glass, having a concrete block broken on his torso while he's sandwiched between two beds of nails, dipping his fingers in molten lead, and picking up an orange-hot piece of space shuttle tile.

From the article:

Before dipping one's fingers in molten lead, the hand is dipped in a bowl of water. Then the drops are shaken off and the hand dipped quickly in and out of the lead. I usually dip the first seven or eight centimeters of my fingers. Heat from the lead goes into evaporating the water and hence not into burning the hand, and the resulting steam layer insulates the hand.

He's also famous for his barefoot fire walking. I wish my science teachers had been so engrossed in their work.

The Physics Behind Four Amazing Demonstrations

Article written by Alan Bellows, published on 24 December 2005. Alan is the founder/designer/head writer/managing editor of Damn Interesting.

Article design and artwork by Alan Bellows.
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15 Comments
Arcangel
Posted 24 December 2005 at 10:25 pm

Even with a disclaimer you still get people willing to try these stunts and they end up getting hurt. Your science teachers probably didn't want to lose their jobs or worse get sued by parents who's kids try and imitate these things with bad results. I have heard news stories on people walking barefoot across hot coals and ended up with severe burns on their feet. The fingers in molten lead is new to me but hey some people will do anything for a kick out of life. Still a damn interesting article though.


Daniel Lew
Posted 24 December 2005 at 10:40 pm

I use the same physics principles behind putting the hand in molten lava to put out candles with my fingers. It's fun to see that the same trick can be taken to an extreme level.


white_matter
Posted 24 December 2005 at 10:56 pm

The same concept behind dipping your fingers in the molten lead can be applied to "burning" a dollar. If I remember the process correctly, you first soak the dollar in water and then dip it in lighter fluid or some other flamable liquid and blaze away. The fluid burns off and the water acts like an insulator. If anyone were to want to try this though, I would recommend starting off with a 1 dollar bill. :)


scribby
Posted 25 December 2005 at 10:47 am

I had an 80 yr old plumber teach me how to do this by using saliva. In either case, be sure to get the underside of your fingernails wet. I've heard it hurts a lot if one leaves that "uninsulated". --scribby


Diegost
Posted 25 December 2005 at 03:04 pm

Reading this makes me wanna study physics, and I don't like them at all. Interesting how a non-conventional teaching can change your view of subjects you disliked.


Bryan Lowder
Posted 28 December 2005 at 01:55 pm

I believe Jearl Walker invented this demo. He included the caveat that if the lead isn't really really hot, a lead "glove" would form around your hand and give 3-degree burns. He eventually gave up on the demo after he got numerous scars on his face from splashing lead. To demonstrate the same principle, the "Leidenfrost effect", he would also roll liquid nitrogen around on his tongue. He quit after a scolding from his dentist when the lN2 touched his two front teeth, shattering the surface into a "road map" of cracks. I think this was an article in the 1979 or 1981 edition of _Principles of Physics_ by Halliday and Resnik.


simonster
Posted 29 December 2005 at 04:28 pm

Jearl Walker does the fingers in molten lead and the bed of nails tricks in the video series Kinetic Karnival. If you ever have an opportunity to see these videos, do. They're hilarious. Jearl Walker makes remarks every couple of minutes about how incredibly masculine he is for doing these things. This page has some great stories about the bed of nails trick gone wrong...


WolfManDragon
Posted 27 June 2006 at 12:34 pm

The smelters at Mahle are notorious for dipping their wet fingers into the alloy pour pots.


campo
Posted 10 December 2006 at 02:48 am

Someday some student is going to try this at home. Dipping his fingers into a molten substance and pull back out with only his knuckles.


Cathryn
Posted 30 December 2006 at 12:33 pm

thats wierd


Merciless
Posted 12 June 2007 at 01:43 pm

Its not really that interesting if one is aware of the physics behind the trick. I wonder if alcohol was ever an influence in any of them. Wouldn't suprise me. For instance. I witnessed my brother on a camping trip sitting around a nice blazing fire pick up one of the amber red logs out of it then put it back. Of course I think it was a stupid thing to do and was glad he didn't scar his hand or worse, be stuck with nubs for fingers. Haha! I suppose looking back now that it could have been the tiny layer of already burnt log.


khendar
Posted 05 September 2007 at 11:30 pm

The hot coals one is easily explained. Coals and the ash coating them has very low thermal conductivity, so that even though they may be at 500+ degrees, they will not easily impart that heat to a bare foot walking across them (or a hand picking them up).


Josh Sincer
Posted 06 April 2008 at 04:32 am

It's not that straightforward. What about Shaolin monks for example? or Yoga? I think in eastern tradition they need many years of trainings to be able to do such things. However, for sure, there are people who play tricks and foul the audience only:)!


a1c
Posted 09 August 2008 at 06:12 pm

Cooking with LOX is fun too.

http://www.youtube.com/watch?v=TBLr_XrooLs


MacAvity
Posted 19 December 2009 at 06:55 pm

Another fun demonstration sure to hold students' attention is thus:

The professor dips his entire, gloved left (assuming he's right-handed) hand into liquid nitrogen and holds it there for a few seconds. He pulls it out, steaming with sheer coldness, thoroughly frozen and unable to move. He places it with a frozen sort of "thunk" sound on the table, and, before the astonished students can think, picks up a hammer with his unfrozen right hand and smashes his left into smithereens.

He then drops the splintered remains of the disposable glove and whatever bits of frozen hamburger may still be attached to it, waves his undamaged real left hand, wiggles its fingers, and explains about the ground beef trick amidst relieved laughter and students' boastings to each other about how "I knew he was faking."


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