Detecting Appearance Changes with Spectrocolorimetry and Densitometry

Abstract

Several types of ink jet prints, each containing cyan, magenta, yellow, black and grey areas, were exposed to various indoor lighting conditions that can cause fading or other appearance changes. Alterations in appearance were monitored by reflectance spectroscopy with a portable spectrodensitometer. Both CIE L*a*b* and Density T values were recorded for each measurement made during the course of the exposures. The instrument is capable of detecting trends of change in the samples before any appearance changes are noticeable by eye. The data have been evaluated to determine which system of describing appearance is more sensitive for detection of fading, for each of the colors used.North skylight, which was filtered through window glass and thus contained a substantial component of UV A, was used to cause rapid fading of some samples. Light exposures that mimicked museum exhibition conditions - tungsten lighting filtered through UV blocking plastic glazing - were also used. As expected, the colorants were much less fugitive in these latter conditions. Most colors withstood total experimental exposures equivalent to that which would be endured over several thousand hours of gallery exhibition, before the extent of change detected was considered significant.