For Evaluating Mottle, Holdout and Porosity of Coated and Uncoated Papers
These testing inks provide a simple and rapid way of monitoring batch-to-batch variations in paper structure and porosity. Inks of both high and low penetrations are required because the penetration quality of the ink must be appropriate to the holdout of the paper surface being tested. Coated papers, being relatively high in holdout, require a high penetration ink to obtain a sufficiently strong color and mottle pattern.