I worked at a facility with experimental lithography machines. One of the
nasties looked like water, but would pass through your skin and melt your bones. Fun.
Hydrofluoric acid, though I don't think it melts your bones in a dramatic/fast way. It seems to be partially so dangerous because it doesn't "burn" right away, and as you say, is absorbed quickly in skin. So you might not rinse it off quickly.
"Piranha solution" (sulfuric acid, water, and hydrogen peroxide) is closer to what tv/movies portray hydrofluoric acid being like. That is, being able to disappear a body in it.
> It seems to be partially so dangerous because it doesn't "burn" right away, and as you say, is absorbed quickly in skin. So you might not rinse it off quickly.
It seems to be dangerous in a lot of different horrible ways. It's always fun reading an MSDS for substances like this: https://www.airgas.com/msds/001077.pdf
I worked at IGNS in NZ and they used it for dissolving rocks. Many warning signs.
[edit: to clarify I mean safety warning signs, not warning signs of being in contact with it. My assumption is excruciating agony which would be a good indicator :D]
HF keeps regenerating itself until it hits bone and forms calcium floride. Get exposed to enough of it and it will pull the calcium out of your cells, stopping muscles, heart beats, and neuron firing.
I'm not sure what concentration IGNS was using it in as I'm mercifully a computer person, but I had a friend who worked in their labs and took me through them one time :D