The colourimetric match is checked by printing each ink of the ink set to be tested on the reference substrate (C2846) with different ink film thicknesses. The sample prints are made for this purpose in accordance with the ISO 2834-1:2020 standard. The printed colours of the resulting test prints are measured colourimetrically in accordance with the ISO 13655:2017 standard. Subsequently, the colour difference between the sample and the corresponding nominal value from the standard ISO 2846-1 is determined. If at least one of these samples is within tolerance, the printing colour is colourimetrically in accordance with the.
The transparency value T is determined by printing each of the chromatic colours (cyan, magenta, yellow) on a black substrate at different ink film thicknesses. The colour difference ΔE*ab is determined for each sample between the overprinted and the unprinted black substrate. Subsequently, the slope of the linear regression of the ink film thickness against the colour difference is determined.
A printing ink complies with the requirements of this standard with regard to transparency if the reciprocal of the slope is negative or greater than the specified value.