Procedure for making coating color was followed as given in reported work [11]. Required weight of calcium carbonate slurry was taken in beaker and kept under agitation. Clay slurry and calculated amount of water were added to it to get targeted solid concentration. Starch paste was added slowly in pigment slurry to avoid any viscosity shock or lump formation. The speed of the agitator was lowered to avoid any foam formation during addition of synthetic binder. CS was then added slowly into the slurry. Lubricant, insolubilizer and synthetic thickener were added at the vortex after fixed interval of time. Finally OBA was added to the color. The pH of the color was adjusted to 8.5–9.0. The total solids of coating slip were kept around 50%.
The coating color containing various parts of CS with other ingredients was prepared as given in Table 2. Coating color formulation marked “control” was prepared without addition of CS. The parts of GCC and other additives were fixed throughout the experiments in all batches (marked as A to F).