In the current version of DF, dwarves will clean themselves at a well. A dwarf with blood or pus or forgotten beast extract will stand next to a well, lower and raise the bucket, then walk away clean, leaving a puddle of whatever he washed off behind. This will often get on whatever dwarf uses the well next, leading to an endless cycle of re-contamination.
I've been trying to figure out a way to clean up this residue between uses. Water isn't reliable at moving contamination, more likely to spread it around than remove it. Placing a grate doesn't work, since contamination doesn't fall through grates. Magma would remove the contamination, but a system to flush the well with magma between uses without clogging the whole thing with obsidian would be complex.
Then I realized that I'd seen fire remove blood splatters in adjacent tiles. And I realized that artifacts burn forever. So I thought, make a well with a forgotten beast bone chain I have lying around (and otherwise magma-safe materials), set it on fire, and it will then clean itself between uses.
Yeah, this was a terrible idea. I set the well up and set it on fire with a carefully managed magma wave. When the magma was gone, I channeled out the rest of the space under the well to connect it to the cistern. A dwarf with some mud or something on his feet came by to use the well. He lowered the steel bucket into the cistern, at which point the burning chain began boiling the cistern water away. Despite this, the bucket managed to fill with water. The dwarf raised the bucket, which boiled dry the moment it left the water. Rather than canceling the job, the dwarf lowered the bucket again ... repeating the cycle over and over again, until the cistern boiled dry and the job canceled. He then walked away, leaving the burning chain lowered to the lowest level of the cistern, and also leaving a trail of blood as most of his fat had melted out at this point.
I couldn't refill the cistern for the burning chain lowered into it. I managed to deconstruct the well, and luckily the rope ended up next to where the well was built rather than falling into the cistern. Now I have a permanently burning forgotten beast bone rope in a locked-off corridor, and a steel bucket at the bottom of the cistern.
I'm still looking for a way to make a self-cleaning well. This was not the way to do it. Amusing, but a terrible idea in retrospect.