The Correlation of Macro Print Mottle to Surface Topography as Measured by an Optical Surface Topography System

A group of coated and uncoated printing grade papers was tested on a new instrument that displays and objectively quantifies the surface topography of paper and board. The numeric ranking from the instrument was then correlated to the quality of the print produced on offset and rotogravure presses using an objective print mottle measurement and, for coated board, with expert evaluators.

Images generated by the topographic instrument are presented for visual comparison of the surfaces studied. This new instrument, can measure, in one action taking less than 30 seconds, the topography in areas as large as 200 mm x 200 mm. In the experiments conducted on coated board the entire area was measured as a unit. In the print trials the instrument software enabled the large imaged area to be sub-divided to measure and report the unprinted surface topography separate from the mottle measurement in the printed areas.

It is demonstrated that the Verity-Topo instrument can emulate the human in visual printing surface evaluation and holds a great potential to objectively predict the quality of print based upon surface topography measurements. The methodology tested and described in this paper is applicable to any surface destined to receive a printed image using a contact printing method and may have application to non-contact print.