REXOGRAPH

Rexograph machines were spirit duplicators used from the 1960s through the 1980s — also sold as Ditto, Banda, Gestetner, Rex-Rotary, and Hectograph machines. They produced the purple-tinted, grainy copies most people recognize from old school handouts and church bulletins.

The master's underside was coated in aniline dye — usually violet, since it was the cheapest pigment that worked with the process. Writing or typing on the master transferred a reversed, waxy image of dye onto its face. Loaded onto the machine's drum, each blank sheet passed through moistened with a thin alcohol solvent that dissolved a little of that dye and pressed it onto the paper. A master held a fixed dye reservoir good for roughly 50-400 copies, so later copies in a run came out fainter and patchier as it depleted — that's what the Run Progress control below models.

Two more, unrelated causes of aging: acidic paper stock yellows and grows brittle over decades on its own (Paper Age), and aniline dye is notoriously light-sensitive, fading toward grey-blue with cumulative light exposure (Light Exposure) — separate physical processes from the print run itself, which is why they're independent dials.

This site recreates all of that digitally: the grain, the streaks, and the uneven ink density that made every copy off the same master slightly different — minus the solvent smell.