Breast, Eric? Ah, memory, ah, senility. :-(
Not quite, Rob. But I'm glad you asked.
It's actually the result of what happened when I put the glossy paper into my printer the uncoated side up (Ah, senility!)
The printer left puddles of black ink all over, but it looked sort of interesting, so I left it sitting not-quite-flat for a couple of weeks to dry, which it almost did.
I was actually printing three B&W prints and the stack of paper went in wrong side up.
The results look sort of interesting, so I photographed the results, and I think I'll do some more experiments.