Investigations have been made to find practical measurement methods for metallic offset inks. Laboratory-based tests and on-press tests were conducted utilizing a variety of metallic colors based on the Pantone(r) metallic book. The inks were tested in regard to polarized and non-polarized density measurements, gloss and color measurements using spherical and non-spherical spectrophotometers.
Results showed that cyan density readings done with a polarized densitometer represented best changes in ink film thickness regardless of the tested color. Gloss measurements done at three different gloss angles showed that the 60deg angle proved the most reliable.
From the three colorimetric values L* indicated change in ink film thickness. L* measurements were conducted with a spherical spectrophotometer.
These three parameters were used to evaluate press sheets which were also analyzed for a visual match to the Pantone(r) book. From the three measurements, cyan density, gloss, and L*, the L* value was in direct relation to the printed color in the Pantone book. L* measurements done with 0/45 geometry-based spectrophotometer gave a wider range in values but were not as accurate as the spherical measurements in relation to a visual match.