Some of us like a patina

Thanks to Christopher Lee, Paul Smith and everyone on SFI for the interesting discussion on patina (rust) and piss. Thanks especially to bladesmith Howard Clark for this, forgive me, nugget:

The nicest patina for steel is brown, IMO. The best way to apply that look is to deliberately rust the tsuba, the with a stiff brush or steel wool take all the "loose" rust off and rust it again, repeat the process until you are happy with the color. Then if you want it to turn black instead of brown, boil it for a few minutes in clean water. Urine works fine as a rusting agent. If you have a cat, you could bury it in the litter box. Cat urine will make it black very quickly (don't ask me how I know this). Most any slightly acidic liquid (water based) will induce rust. For best results you need a "damp box" (closed container to promote high humidity and warmth). Good luck.

Thank Odin for the internet. Every single day.

Or thank Thoth. Or Oghma. Or somebody.