This photograph illustrates the main ways in which pictures and texts not intended to look like printing were produced in the nineteenth and early twentieth centuries. The plough is an electroplate, a durable form of illustration block made by impressing the wood or steel original in wax, rubbing the wax impression with graphite, and electroplating it with copper, which was then backed with type metal. To the right is a half-tone engraving, made photographically onto a zinc plate, the most common method for illustrating newspapers. Beneath the relief cuts is a lithographic stone with a variety of labels and a business form. Lithography works by printing from a treated surface, originally stone, that rejects ink in some places and holds ink in others; when the stone is wiped, the image retains ink which can then be transferred to the paper to be printed. One end of the stone shown has reversed images, for direct lithography, in which the image goes directly onto the paper while the images on the other end are not reversed, for offset lithography, in which the image is transferred to a rubber roller and from the roller to the paper. Photographic offset lithography, using flexible plates instead of stone and photographic images instead of artwork, is now the normal method of printing in Canada.
