Once design completed multiple copies of image printed onto special photographic glass plate (multipositive plate). Strong light is passed through multipositive plate causing images to be fixed onto carbon tissue paper coated with light sensitive gelatine. Carbon tissue then wrapped around a resin covered copper plated cylinder. Film "developed" by sprayingcylinder with hot water. Leaves the film of gelatine adhered to resin. Amount adhered varies in thickness in proportion to light and shade of photographed images.
Etching solution (contains ferric chloride) burns off gelatine in proportion to its thickness (The thinner the gelatine the deeper the recesses on the cylinder and the deeper the tones produced). Control marks, cylinder numbers
, register lines, perforation guides added. Following checking of cylinder proofs (printed usually in black) for errors and after corrections, cylinders are chromium plated and ready for printing use.
Pre-watermarked paper (obtained from John Aiken Ltd of Portals) in large reels gummed with gum arabic from Sudan (supplied by Samuel Jones Ltd) were used.
Photogravure printing machines (also called web-machines because they printed a "web" of paper) used were specially constructed by Timson Ltd of Kettering. Worked on rotary principle.
Each revolution printed one double pane sheet i.e. 2 x 120 stamps.
Stamps were then guillotined as double pane sheets and perforated prior to final checking, packing and despatch.