Photoglyphic engraving

William Henry Fox Talbot's improved process for producing a printing plate from a photograph was patented in 1858. After coating a copper plate with bichromated gelatin, Talbot exposed the plate to light under a positive transparency. It was then dusted with powdered resin and heated evenly to distribute the resinous particles. The plate was then etched in an acid solution that dissolved the gelatin and etched those same areas. After cleaning, the plate was inked, wiped, and printed on paper. He coined the term photoglyph from the Greek for "carved light."