Common types of paper include coated paper, copperplate paper, and white cardboard.
Paper is a thin layer of material made by interlocking plant fibers. Therefore, the basic component of paper is plant fiber. Paper is made by processing plant fibers through chemical and mechanical methods, and they are interwoven into a porous thin film. Papers with different uses should have special properties based on common properties. These special properties are achieved by selecting different types of plant fibers or adding different proportions, types or quantities of additives, and processing them with different mechanical equipment.
1. Coated paper (Dowling paper)
Coated paper is divided into special grade, No. 1 and No. 2 according to the pulp ratio. It can be single-sided or double-sided, and has two levels: super calendering and general calendering. The weight of the paper ranges from 50g/m2 to 180g/m2, with commonly used double-sided coated paper being 70g/m2, 80g/m2, 90g/m2, 100g/m2, and 120g/m2, and single-sided coated paper being 50g/m2, 60g/m2, 70g/m2, and 80g/m2.
Coated paper has low ductility, uniform ink absorption, good smoothness, dense opacity, good whiteness, and strong water resistance. It is used to manufacture thin paper packaging and decorative prints. When printing on coated paper, the paper should not be stacked too high, especially for prints with high ink volume and high smoothness, which should avoid being dirty on the reverse side. Generally, anti-soiling agents, powder sprays, or interlining paper can be used. Resin-based offset printing ink and high-quality lead printing ink should be selected. The viscosity of the ink should not be too high, otherwise powdering and hair loss may occur.
Coated paper is mainly used for offset (lithographic) printing machines or other printing machines to print high-grade colorful prints, such as colorful magazines, albums, promotional posters, color printed trademarks, and some high-end book covers and illustrations.
2. Copperplate paper
Copperplate paper, also known as coating paper, is a high-end printing paper made by applying a layer of white pulp to the original paper, and then processed by super calendering. It is also known as printing coated paper. It has high whiteness, uniform distribution of paper fibers, uniform thickness, small ductility, good elasticity, strong water resistance and tensile strength, and excellent ink absorption and reception status. When printing on copperplate paper, the pressure should not be too high, and resin-based offset printing ink and glossy ink should be selected. To avoid dirtying the reverse side, anti-soiling agents and powder sprays can be used.
Copperplate paper is mainly used for printing albums, covers, postcards, exquisite product samples, and colorful trademarks.
3. White cardboard
White cardboard is a kind of packaging paper used for printing various trademarks and packaging boxes. It is available in weights of 220g/m2, 240g/m2, 250g/m2, 280g/m2, 300g/m2, 350g/m2, and 400g/m2. White cardboard is composed of a bottom layer and a surface layer, and the surface layer is white, while the bottom layer is generally the nature of the raw material. White cardboard can be divided into powder surface white cardboard and general white cardboard according to the surface layer, and gray bottom and white bottom according to the bottom layer. The quality requirements of white cardboard are: bright, smooth, uniform thickness, texture firm, non-powdering, non-hair loss, and uniform ink absorption. It has small ductility, durability, and does not crack when folded.
White cardboard is mainly used for printing packaging boxes and product decoration lining paper. In bookbinding, it is used for the inner lining of simple and fine binding books and the binding material for the spine of hardcover books.
4. Letterpress paper
Letterpress paper is the primary paper used for letterpress printing of books and magazines. It can be divided into four grades according to the different ratios of paper materials, including grade 1, grade 2, grade 3, and grade 4. The grade of the paper represents the degree of paper quality, and the higher the grade, the worse the paper quality. The weight of the paper is (49~60)±2 (g/m2). Letterpress paper is mainly used for letterpress printing. Its characteristics are similar to newsprint, but not exactly the same. The pulp ratio and beating of letterpress paper are better than those of newsprint. The fiber structure of letterpress paper is relatively uniform, and the gaps between the fibers are filled with a certain amount of filler and adhesive. In addition, it is also bleached, which makes this type of paper more adaptable to printing. Although its ink absorption is not as good as newsprint, it has the characteristic of uniform ink absorption. Its water resistance and whiteness are better than newsprint.
Letterpress paper has the characteristics of uniform texture, no fluff, slight elasticity, opacity, and some water resistance and mechanical strength.
It is suitable for the main text paper of important works, scientific and technological books, academic journals, and college textbooks.
5. Embossed paper
Embossed paper is a special paper produced for cover decoration. The surface of the paper has a slightly obvious pattern. It comes in colors such as gray, green, beige, and pink, and is generally used for printing monochrome covers. Embossed paper is brittle, and the spine is prone to cracking during binding. When printing, the paper has a greater degree of bending, which makes it difficult to feed the paper and affects the printing power.