For Evaluating Mottle, Holdout and Porosity of Uncoated Paper
This testing ink provides a simple and rapid way of monitoring batch-to-batch variations in paper structure and porosity. Uncoated paper, being low in holdout, require a low penetration ink, such as TK-21, to avoid excessively strong color that would overwhelm any mottle or holdout distinctions.
Test Procedure: Spread the ink on the paper to be tested using a spatula or drawdown applicator. After one minute remove the ink by first scraping off most of it with a straight edge, then wiping away the remainder carefully with a clean paper towel. The resultant test pattern is characterized visually for mottle and porosity. To obtain an instrumental value for porosity, measure the CIE-Y reflectances, or the densitometer values, of the stained and unstained areas, then calculate: