I'd like to write on some prints of mine, back and possibly front. As of now, they are RC prints, but there will be some FB prints too at some point. I'd rather not use something like a Sharpie, since they fade with light and generally aren't archival. However, I'm having problems finding something that will actually write on the back of an RC print, stay, and be waterproof. There's got to be something out there... I'm ok with using a fountain pen or a dip pen if that's what needs to happen. Actually, I'd rather do that then buy some kind of pigment-based marker. So if anyone has recommendations for specific products that they know work, that would be great.