What is immediately obvious about the below picture is that we're looking at a finger print. What ISN'T immediately obvious is that we're also looking at scale build-up on the inside of a boiler. I think the clear take-away from this is that we ought to take care not to touch the inside of a boiler after doing a descale. It'd appear that the transfer of oils from our hands provides minerals a with a place to adhere to the surface of the boiler.

The first thing that came to mind when I saw that was. "One.. small.. step for.. man... One giant leap... for Mankind. kchhhh."

Eh, the first thing that came to my mind was "Hey! You're the one who stole my... ! ". LOL

That is very interesting though. That the scale will grow on the fingerprint. A very cool CSI moment...

Wow, your finger print has just been fossilized; it'll be a museum piece in 10 million years.