Independent discoveries around the turn of the century by the inventors Ira Rubel and Alfred Harris demonstrated that an image from a lithographic plate wrapped around a cylinder could be “offset” onto another cylinder wrapped in a rubber blanket and printed from there onto a sheet of paper. Equipped with the new presses, lithographic printers found they could routinely achieve results with the offset process that were difficult or impossible with relief. The most important advanatage of offset was the ability to print every dot in a fine halftone on rough or textured paper, because the resilient rubber offset blanket carried the image into every crevice. Offset prints also had a softer appearance, in contrast to the hard edges characteristic of a relief-printed halftone. Offset printing of color halftones became well-established by the 1920s, but letterpress did not lose its grip on text printing until the 1950s when photocomposing machines did away with the need for metal type.
This image was printed in six colors on a Harris offset press by Waterlow Bros. At the time this issue of the Penrose Annual was published, offset printing had been around barely six or seven years, but was already making inroads into territory formerly held by the letterpress printer. In an accompanying article to this illustration, it is noted: “Special attention might also be drawn to the purple, which we believe is always a difficult colour to produce on any lithographic machine. It is generally contended that colour work produced on an offset press invariably shows dull, but upon referring to the picture under discussion it will be readily seen how full of life the colours are.”