In the last few years, interest and demand of high bright paper have forced paper manufacturers to
think new ways to improve brightness and whiteness of coated paper. Pigment coating is widely used to
enhance the optical properties such as brightness, whiteness, and gloss of paper and paperboard. These
optical properties are the most important for end user and also determine the final cost of coated paper.
Calcium sulphate has inherent better optical properties compared to other conventional pigments for
example ground calcium carbonate, precipitated calcium carbonate and kaolin clay. The present study
was carried out with an aim to synthesize calcium sulphate using waste procured from phosphoric acid
industry and to study its impact on the rheology of coating color as well as optical properties of coated
paper. Addition of calcium sulphate improved the water retention property of coating color which can
be helpful for improving the machine runnability. The results also revealed that calcium sulphate can
be used as a pigment to produce coated paper of high brightness and whiteness. The brightness and
whiteness of the coated paper were improved 4 and 15 points, respectively by using 50 parts of calcium
sulphate as a pigment replacing clay from the coating formulation. The surface strength in terms of IGT
pick value of coated sheets was found significantly comparable using calcium sulphate as pigment. The
print gloss results were observed analogous with matt grade coated paper.