Dynamic Monitoring of Water During Lithographic Printing.

A portable near-infrared moisture meter has been utilized to track water during the lithographic printing process. The absorbance at 1.94 um is used to monitor water without interference. An angular dependence was found for aligning the meter a few degrees off perpendicular when monitoring various substrates. Water was measured in newsprint at various stages of a press run before and during printing. It was also monitored in ink on both the image and non-image areas of the plate as the water settings were changed on press. Differences in the equilibrium distribution of water on plate for a spraybar and Molleten dampening system were followed. The relevance to ink/water balance during lithographic printing is discussed. The sensitivity of this approach for non-contact measurement is demonstrated for various applications.