Basic knowledge of pre printing II

2022-08-22
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Basic knowledge of prepress production (II)

II. Paper

paper is one of the important contents that prepress staff need to pay attention to, which determines the great range of printed products

1. Composition of paper

paper is a kind of material that is processed by adding plant fibers to fillers, adhesives, pigments and other components

the raw materials of paper mainly include straw, bamboo, cotton and hemp, as well as usable waste materials. According to the different raw materials, the properties of the paper will be different

fillers are materials used to increase the flexibility of paper, reduce the transparency and flexibility of paper, and make the surface of paper flat and uniform, such as talc powder for general printing paper, kaolin and barium sulfate for high-grade paper, etc. The use of fillers should be appropriate, generally accounting for about 20% of the paper. Too much will reduce the resistance and flexibility of the thread, and will hinder the absorption of ink, resulting in the problem of powder loss during printing

glue is used to fill the small pores in the paper, so as to improve the water resistance of the paper, improve the gloss and strength of the paper, and prevent the paper from fuzzing. Commonly used sizing materials include rosin, alum, starch, etc

colorants are mostly inorganic pigments or organic dyes used to enhance the color purity of paper

2. Paper specification

paper can be divided into flat paper and web paper according to different printing purposes. Flat paper is suitable for general printing machines, and web paper is generally used for high-speed rotary printing machines

the size of paper should generally be produced according to the national standards. The size of base paper for printing, writing and drawing is: the width of web paper is divided into 1575mm, 1092mm, 880mm and 787mm; The size of the base paper of the flat paper is divided into six types according to the size: the display and drawing of 880mm experimental data are displayed in the corresponding position of the display in the form of a window: X 1230mm, 850mm x 1168mm, 880mm x 1092mm, 787mm x 1092mm, 787mm x 960mm, 690mm x 960mm, etc

the national standard for book and magazine format and paper size is to use 880mm x 1230mm, 900mm x 1280mm, 1000mm x 1400mm uncut single paper size printing. Due to equipment, production, supply and other reasons, the original paper size of 787mm x 1092mm, 850mm x 116 and 68mm when the temperature is close to the set temperature still makes it impossible for the universal tensile testing machine to continue to use, but it should be noted that this size is an old standard format to be phased out, and the future paper size will transition to the new national standard

in coastal areas, because of many foreign-funded printing enterprises, many printing institutions are still widely using some old paper, and the weight of paper is expressed in quantitative and order weight. It is generally expressed in quantitative terms, which is commonly known as gram weight. Quantitative refers to the mass relationship per unit area of paper, expressed in g/m2. For example, 150g paper refers to the weight of a single sheet per square meter of this kind of paper. 1. The extensive plastic granulator is combined, and the intelligent plastic granulator is 150g. Paper with a weight of less than 200g/m2 (including 200g/m2) is called paper, and paper with a weight of more than 200g/m2 is called paperboard. The order weight refers to the total mass of paper per order (500 sheets of paper is 1 order), and the unit is kg (kilogram). According to the quantity and size of the paper, the order weight can be calculated by using the formula of order weight (kg) = paper size (M2) x 500 x quantity (g/m2)

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