I tested three new writing media for the backs of photographs. I recently went through some 2 or 3 year old pictures I had marked with Higgins Black Magic. In exactly one case I found one photo that had picked up pen marks from another. I do not know if I put them together while the ink was still wet, or if the ink adhered over time. I was displeased, though no harm was done to the pictures.
I suspect the cause is that Higgins Black Magic is a latex-based ink. Like latex paint in a house, it never fully loses its stickiness. I decided to round up a couple more candidates, and I have two new winners and a loser to add to the mix, and one more loser.
I bought a Copic Multiliner SP pen in 0.03 mm (very, very, fine line) and tried it. This pen uses a fiber-filled cartridge refill, so you can’t change the ink. As the unaltered scan shows, after one minute it smeared badly. After an hour or more it seems pretty stable, but it is such a light grey that it is miserable to read.
The second test was a product labeled “Royal India Ink Encre de Chine” by Reeves & Poole Group. This smells like alcohol and is almost certainly a shellac-based product. Like Higgins Black Magic the Reeves & Poole leaves a slightly embossed feeling on the paper, but goodness it writes well on photo paper. I do not know if it is archival. Shellac cleans easily with denatured alcohol, which is cheap in a gallon drum from the home center. I doubt it would be safe in a technical pen.
The clear winner is the Rapidograph Black India Universal 3080-F.BLA ink, which left less embossed character on the photo paper, dried almost instantly, and is safe for technical pens. Or at least as safe as anything can be in a pen that requires cleaning. This ink may also be shellac based, it smells of a solvent that is more lacquer-like than latex-like. As with most other inks, I can find no data about archival quality.
The technical pen is much easier than a dip pen and inkwell when your desk is cluttered with photos you are scanning. I am pleased to report this is probably my new go-to ink for photo work.