Have you ever tried D-19. I use it a lot to make Efke IR and HP5 negatives print in carbon transfer. I also dabbled with x-ray (14X17 double-sided, green latitude) as a dupe film a couple of years ago and was pleased with the results. Dilute the stock 1:1 to 1:3.
Andrew, is the Efke IR the ISO 25 (?) speed. I have a couple hundred sheets in the refrigerator in 11x14. I've never used it, is D19 pretty much required for carbon printing? I was going to use Pyrocat HD. Does D19 produce usable carbon negatives? I've heard it suggested many times.
Everytime I find a film or paper that I like, they discontinue it. - Paul Strand - Aperture monograph on Strand