The Use of X-Ray Emission Analysis as an Absolute Measurement of Ink Film Thickness and Ink Trapping.

The importance of the ink film thickness (IFT) on final reproduction and print quality is discussed, followed by short review of the methods used for IFT measurement. The IFT was measured by a Gravimetric method, and compared with measurements obtained by an X-ray emission analysis technique. A linear correlation was obtained. A preliminary calibration was made for single colours and experiments performed to determine whether these calibrations are applicable to the trapping of overprint colours. X-ray emission analysis is a method of determining the quantity of a particular element present in a thin film and avoids the problems associated with optical densitometric techniques. A pilot study was undertaken to determine which elements can be used to identify a particular ink and allow sufficient precision in measurements. Results are presented on the trapping properties of two inks on a number of paper types. Most previous work has concentrated on solid overprints but in this instance the relative ease and precision of measurements has allowed a wide range of tints to be investigated also. Printing was carried out in a normal commercial environment so that the results have validity outside artificial laboratory conditions. outside artificial laboratory conditions.