In the development of custom
SPOT color inks, there will be only a single combination of pigments that will produce the correct color for both the
solid tones and for one or more halftones intermediate between the full tone and the unprinted substrate. A novel
system and method is presented for finding such a combination of colorants without requiring a complex suite of
software algorithms. The method includes a search of a
library of known
colored inks printed onto a specified substrate and printed using specified printing conditions. Each
record of such a
library can contain, for example, the ink formula, the combination of colorants and resin, the spectral
reflectance factor of the ink and substrate, color values (XYZ and CIELAB) of the
solid ink color (100% tone) and 10% steps down to 0% (unprinted substrate). In such a
database halftones can be specified in units of % (0% to 100%), but can also, for example, be given as 8-bit integers (0 to 255). In exemplary embodiments of the present invention, such a search locates the
solid ink color that meets the color requirements and simultaneously meets the color requirements at one or more intermediate
halftone steps. The claimed method can thus achieve a
printing ink formula that produces a color match to a customer proof at both the solid color and at one or more halftones with ink coverages
lying between the unprinted substrate (0% tone) and the fully printed substrate (100% tone).