Well I find this all very interesting. I have tons of waste imagesetter output; now I can scavenge all the pieces that are fully black, cut them into 6.5x9 cm rectangles, and bleach them to play with in my old Zeiss Ikon Maximar A. I could probably rustle up 100 or more cut sheets like this from the scrap output I have.

The film is imagesetter film, it's been developed and fixed, but that should not matter, should it? The imagesetter produces high contrast graphic output, so black is very black.