Additional experiments using water-based inks were per- formed to identify the location of the failure for the two- layer coatings. One drop of water-based black ink was added to the 10 pph SB latex anionic formulation, and one drop of water-based pink ink was added to the 10 pph SB latex cationic formulation. The purpose of the addition of the ink to the coating formulations is to identify each layer in the IGT pick test [21]. The addition of the inks did not change the zeta potential of the coating formulations.