Originally published at: What would happen if you swiped your hand underneath an extremely powerful water jet? Spoiler: Don't. | Boing Boing
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I used to work in a machine shop in my early twenties when water jet cutting tech was being introduced. I believe there’s water jets that are even more powerful out there these days, the kind that cuts through metal and won’t turn on unless the cage door is closed first. 
ETA:
Theoretically, there is no limit to the thickness of steel that advanced water jets can cut. However, when cutting an exceptionally thick piece of steel, the time taken increases significantly, making the process unfeasible.
Therefore, waterjet cutting machines usually cut up to 6 inches of steel. But commercially available machines can handle up to 9 inches as well.
In some applications, advanced abrasive and percussive water jets are modified to cut 18-inch thick steel blocks; however, such thickness isn’t commonly used.
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I was never sure if this was true, but a former boss of mine was fond of telling us about the time when he was a young engineer and was part of a group of people getting a tour of a sheet metal shop where they did hot dip galvanizing, and some idiot on the tour was standing next to the tank of molten zinc and said, “Is this hot?” and dipped his finger in it. His finger was gone but apparently the wound was also cauterized, so…
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Not so sure, the Leidenfrost effect is a hellova thing…
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Oh yeah I have experience with this and 20 years later, still have a scar on my finger from brief run-in with a very thin high pressure water jet grazing my knuckles.
Meat cutting rooms at the grocery store use them to clean up after spraying a disinfectant (strong chemical solution that literally dissolves meat) cleaner. I went to flip over a knife or something I was cleaning and should have either cut off the sprayer or pointed farther away from my other hand before grabbing with it. Thankfully it just grazed the top of my hand and I stopped it immediately, but it sliced into my hand pretty deep and since it was really hot water, it also cauterized the wound. Looked gnarly for a week or so, but no infection or bleeding.
Who knew in a room of knives and saws that the stream of water was the most dangerous thing?
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“this tool that can cut through blocks of titanium won’t possibly hurt ME”
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Interesting. He said the lead was about 500F and his finger was in it for only 1/6th of a second. Zinc melts at 787F, so that might make a difference, especially if my boss’s tour companion left his finger in for longer than 1/6th of a second. But like I said, I never knew if the story was true or something apocryphal that he’d inserted himself into.
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Wim Hof has a death count and he abandoned his kids so you can just laugh.
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My suspicion is it was an actual incident that got embroidered over time.
Whilst I suspect leaving your finger in molten metal for anything above a fraction of a second would take a superhuman mastery of your pain reflex, I’m also sure that the process of the fingers outer epidermis becoming a swiftly expanding bubble of gas has a high chance of injury. Or at the very least going to hurt a lot.
I’m just fascinated by this particular party trick, as it seems to me the separation between proving how smart you are by dipping your finger in molten metal and proving how stupid you are by dipping your finger in molten metal is so infinitesimally small as to make no odds. 
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I always assume these stories are there to best encourage people not to repeat the mistake. “he was badly burned” and “it took his finger off like a movie special effect” land differently.
Then again, there is no shortage of actual awful results from industrial accidents.
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I have a similar tiny scar from a similar experience.
It was one of those coin-op car washes with the pressure sprayer.
I accidentally put the back of my left hand into the spray a couple of inches from the nozzle. It dug a small hole in the fleshy part between thumb and forefinger.
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Yikes!
I’ve seen some video from I think Russia where some guy was slapping molten metal that was pouring down with his hand. Same sort of thing, his hand was wet and was able to be unscathed.
Never been near a water jet, but my dad sold industrial spray equipment, and the most powerful models could blow the paint off of cars and definitely hurt you at close range.
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Yeah that’s high on the list of mistakes I won’t make again. Three of which all involve scars on my hands for stupid reasons, two of those being in that meat room.
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HE THOUGHT IT WAS OKAY TO SHIT IN THE PUBLIC FOUNTAIN??!! 
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Good judgement comes from experience.
Experience comes from bad judgement.
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My dad told me a story about a guy next to him in hospital who’d gotten too close to the business end of a paint spray gun and got paint in his skin. The docs weren’t really sure how to treat him. Unfortunately he didn’t tell me the eventual outcome.
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According to him he did that like hundred times.
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