I don't think you need to say too much. HCA, fix and selenium will mean nothing to most people. How about something like:
My work is printed on double weight fiber based silver gelatin papers, and archivally processed to the highest standards. The finished work is mounted using acid free materials, ensuring the longevity of your photograph.

You can look at the websites of silver gel printers, and see how they word it, to get more (and better) ideas...