Unique processing?

[parnelli_97]

I saw an ad for unique processing of B&W film, while going through the company's profile I came across this photo. I'm wondering how did they do it? Does anyone know what chemical will cause a Silver Gel print to do this? Thanks for any advice.

hxxp://www.alchemy-ink.com/housing.html

[David A. Goldfarb]

It looks like mordançage. There's a description of the process on the Unblinking Eye website.