Printing

Colour Offset Photolithography

The original lithographic process was based on the principle that grease and water repel each other. The process therefore permits an impression to be made at the same level, contrary to steel engraving. The original design is drawn on a calcareous stone using greasy ink (lithographic). The stone is then treated with chemicals, thus fixing the design in the stone. Next, the stone is wetted and then the ink is applied to the roller. The greasy design holds the ink, while the rest of the damp stone repels the ink. One sheet of paper is pressed on the stone providing a reverse image of the original design.

Offset photolithography is based on the same technique. The approved artwork is photographed and transferred to zinc or aluminium treated plates. This plate is inked and the image is transferred to a rubber cylinder. This cylinder (the blanket) transfers the image to paper. This technique does not reverse the original design and its flexibility allows for the use of several colours.

The final pane of the Historic Land Vehicles series, issued in 1996, was created using this photolithography process. The plate proof represents the second verification signed by William F. Danard, the Canada Post Corporation representative. The comments informed the printer of the details remaining to be corrected before the stamps were printed.

National Archives of Canada, Post Office Department fonds, Acc. 1999-0557 Description of the Item Description of the Fonds

Excerpt of the video on the production stages for the Historic Land Vehicles pane. Provided by the Canada Post Corporation.

Excerpt of the video on the printing tests. Provided by the Canada Post Corporation.

Excerpt of the video on printing. Provided by the Canada Post Corporation.