Specks masking by the coating layer in coated paper made from deinked pulp

Abstract Production of lightweight coated paper (LWC) utilises more and more deinked pulp (DIP), for both economical and environmental reasons. A critical requirement on DIP quality for such grades is the cleanliness of the pulp. Indeed, the coating layer may not fully cover specks in the base paper. The objective of this work was to determine the required specifications of the coating layer to produce LWC with DIP base paper. The specks masking phenomena by the coating layer was studied from both optical measurements on coated handsheets made from DIP, and computer simulations of specks contrast reduction. The impact of coating layer parameters (coat weight and optical properties), base paper parameters (grammage and optical properties) and specks nature (grammage and optical properties) on specks masking is studied.