Filler and Coating Pigments for Papermakers

Historians attribute the Egyptians in the Nile Delta with preparing the first type of paper, from a marsh grass called Cyperus papyrus. They cut the plant’s stem into thin strips, softened them in the river, and then pounded them into thin sheets that were then left to dry in the sun. The resulting sheets were ideal for writing on, and Egyptians, Greeks, and Romans used them for record keeping, spiritual texts, and works of art. Papyrus is the basis of the word paper. The father of papermaking is T’sai Lun, who in 105 AD experimented with a wide variety of materials and refined the process of macerating the fiber of plants until each filament was completely separate. He mixed the individual fibers with water in a large vat with a screen that was submerged and then lifted up through the water, catching the fibers on its surface; when dried, this thin layer of intertwined fiber became what we today call paper. The art of papermaking spread to the Middle East and to Egypt, where it replaced papyrus in the 9th century, followed by Morocco and then Spain (about 1150) and France (1190). Industrial minerals play a major part in the manufacture of modern paper. Originally, because they were less expensive than fiber, minerals such as calcium carbonate (chalk) and kaolin were used as fillers to reduce production costs. Although cost is still an important factor, minerals have become “functional fillers” that impart specific properties to paper, such as improved printability, brightness, opacity, and smoothness. In paper coating, minerals are used as white pigments to conceal the fiber, thereby improving brightness, whiteness, opacity, and smoothness.