This photo-silkscreen was made from a photograph which was printed on Kodalith film.  A screen that had been made light sensitive with gelatin and potassium dichromate was then overlayed with the Kodalith film, and an exposure was made. Where the light hit the screen, the gelatin would harden.  The screen would then be washed with water, and the gelatin that hadn’t hardened would get washed out. Printing involved using a squeegee to press the ink through the areas that had been washed out.