Pigments for Color Carbon
1. The C-M-K UltraStable colorants were aqueous pigment dispersions. The Yellow pigment was a dry powder which was ground and made into an aqueous dispersion.
Originally Posted by Philippe Berger
2. In order to balance pigments for the color carbon process, it is first necessary to identify precisely which versions of the four color pigments will be used.
While the spectral characteristics of specific color pigments made by various manufactures may be quite uniform, aqueous dispersions of the same pigments can vary greatly. The surfactants and dispersants, not the pigment itself, used in the grinding and suspension of the pigment particles, are the chief cause of failure (in terms of cross-linking the gelatin emulsion) in the color carbon process. Some additives inhibit hardening, while others cause spontaneous hardening.
Once the individual pigment dispersions have been selected, the amounts required to achieve a neutral gray balance are a function of (besides their color values) the transparency and density characteristics of the pigments. Adjust (by trial and error) the concentration of pigment in the emulsion to achieve printed solid color densities of at least: Cyan 1.35 - 1.45; Magenta 1.25-1.35; Yellow .90 - 1.0; Black, 1.2 -1.3 . The base fog density ("pigment stain") of each color should be .03 or less.
3. The four color UltraStable pigment films were balanced to provide a neutral gray scale using the same exposure for each color (typically, 3-5 minutes with a 1000W Mercury Vapor lamp). By altering the exposure times from the neutral 1:1:1:1 settings, variations in color balance and density could be achieved in the final print without having to remake the high-resolution screened (optical or digital) separation negatives.