M3 Is for Controlling Metallics
By Martin Habekost, Associate Chair of the School of Graphic Communications Management, Ryerson University
In 2009, ISO 13655 was released to update the way color is measured in the print industry. This ISO procedure lists four measurement conditions labelled M0, M1, M2, and M3. M0 is for all legacy models that do not meet ISO 13655. M1 is measur- ing printed sheets with
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a defined amount of UV light added to the white light, so the optical brighteners in the paper can be excited and included in the measurements. The light source used for these measurements has also been updated.
M2 is the same as M1, but without the extra UV-light excitement. That leaves M3. This measurement condition has been created for special-effect inks, as it says in the standard. The light used for the mea- surement is the same as in M2, but two polarization filters have been added. One is in front of the light source and the second in front of the measurement sensor. The orientation of the grating of these filters is orthogonal to each other. This ensures that no strong spec- ular reflection from the sample influences the color measurement.
In 2015, a study was conducted with a set of 10 metallic offset inks. First, prints were made on the Prüfbau printability tester and then also on an offset press. For the color measurement two M3 capable instruments were used; one was an
X-Rite eXact and the second was a Techkon Spec- troDens. Both instruments measured very similar L*a*b* numbers and also gave quite similar ink den- sity values. The prints were made on coated paper.
In the current study, the test was expanded into metallic flexographic printing inks. The flexo- graphic and offset printed samples were not only printed on coated paper, but also on a board, like those boards used in the manufacturing of folding cartons. A gloss water-based coating was applied to the printed samples to see if that had any influence on the measured color and density values. The same instruments used in the 2015 study were also used in this study.
The results from the current study show that the application of water-based coating has very little effect on the measured color; therefore, the printed ink density can be used for controlling the ink on press. Since the measurements on the folding car- ton board were not influenced by the board or the water-based coating, the M3 measurement mode
TECHNOLOGY
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