The Ditto paper was sold in sets similar to a plain sheet of paper (actually something a bit heavier and stiffer) over a purple sheet – also with some body but similar to carbon paper with the purple facing UP rather than DOWN. When you typed the purple transferred to the plain sheet which, attached to the drum, became the master.
There were various brands – I never saw the gelatin block method.
. The power of the press for the underground during World War II and later, even in the East Village in the ‘60s was the Mimeograph. A stencil was cut by typing, the inside of the drum was filled with printer’s ink, and you could run hundreds of copies, sometimes more.. The purple ink was from a Hectograph. It was a plain piece of paper backed by gelatin colored with gentian violet. Placed on a drum, the inked face was dampened by alcohol which then transferred to print the page. Usually not good for more than 30 copies – 50 if you didn’t care which poor student got an exam and couldn’t read the questions. (But you could get a contact high running lots of them in a tiny room.)
Did you get to use any product involved?