The paper industry, particularly printing and writing paper, is by far the largest volume user of IM. The principal IM used in paper making are kaolin, talc, ground calcium carbonate, precipitated calcium carbonate and bentonite.
Minerals are either used as fillers or as a coating on paper. Some, like talc, are also used in pitch control (absorption of wood resins that tend to obstruct the machines). The use of minerals in paper production increases the speed of the machine performance and fluidity. The final characteristics of the paper (strength, whiteness, gloss, ink retention, etc.) are largely determined by the blend of minerals used.
IM are suspended in water before being incorporated into the process. The minerals are often supplied directly to the paper manufacturers in a slurry form or even produced as an integrated part of the paper process (precipitated calcium carbonate). High quality, glossy paper is obtained by applying a thin layer of IM on the surface of the paper. As for fillers, the final characteristics of the coating and its fitness for use are governed by the nature of the mineral blend.