Coated paper (also known as enamel paper, gloss paper, and slick paper) is paper that has been coated by a mixture of materials or a polymer to impart certain qualities to the paper, including weight, surface gloss, smoothness, or reduced ink absorbency. Various materials, including kaolinite, calcium carbonate, bentonite, and talc, can be used to coat paper for high-quality printing used in the packaging industry and in magazines.
The chalk or china clay is bound to the paper with synthetic viscosifiers, such as styrene-butadiene latexes and natural organic binders such as starch. The coating formulation may also contain chemical additives as dispersants, resins, or polyethylene to give water resistance and wet strength to the paper, or to protect against ultraviolet radiation.
Machine-finished coated paper (MFC) has a basis weight of 48-80 g/m2. They have good surface properties, high print gloss and adequate sheet stiffness. MFC papers are made of 60-85% groundwood or TMP and 15-40% chemical pulp with a total pigment content of 20-30%. The paper can be soft nip calendered or supercalendered. These are often used in paperbacks.
Other types of paper coatings include polyethylene or polyolefin extrusion coating, silicone, and wax coating to make paper cups and photographic paper. Biopolymer coatings are available as more sustainable alternatives to common petrochemical coatings like LDPE (see plastic-coated paper) or mylar.
Printed papers commonly have a top coat of a protective polymer to seal the print, provide scuff resistance, and sometimes gloss. Some coatings are processed by UV curing for stability.
Heat printed papers such as receipts are coated with a chemical mixture, which often contains estrogenic and carcinogenic poisons, such as BPA. It is possible to check whether a piece of paper is thermographically coated, as it will turn black from friction or heat. (see thermal paper)
Book paper is divided into uncoated paper (also called offset paper), coated paper (also called art paper, enamel paper, gloss paper and slick paper) and text paper.