Re: large particles more effective?

How very interesting. I've never seen this before.
Do you have a picture of what this looks like? Was this from an iconic silver solution?

My take on black residue is that it's silver oxide. Which is a compound that we don't hear much of beyond it being bad or unwanted in solution. Though I haven't really heard much about using it topically. To which I'd add, you may have discovered something valuable if this is the case.

Couple more questions:
Does it have a silver sheen to it?
Does it stain?