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Influence of Paper and Ink Characteristics On Dot Expansion

       For dot image printing, although dot expansion is inevitable, how to effectively control dot expansion to make it within the normal specified range is the guarantee to improve the quality of printed matter. Generally speaking, the 50% dot gain value specified in the printing requires that fine products should be < 12% and general products should be < 18%. Influence of Paper and Ink Characteristics On Dot Expansion

       Once it exceeds this range, there will be quality problems such as printing tone loss, density increase, color change and so on. In the prepress production and printing process, certain compensation will be made for the normal dot increase, but the abnormal dot increase is often irregular. Influence of Paper and Ink Characteristics On Dot Expansion

       In this way, reasonable compensation can not be made in the prepress production process, but can only be controlled in the printing process. There are many factors causing dot expansion, but paper and ink are two important materials in printing. Their characteristics and use play an important role in the quality of dot.Influence of Paper and Ink Characteristics On Dot Expansion

Influence of Paper and Ink Characteristics On Dot Expansion

1、 Influence of paper characteristics on dot increase

       The increase of dot has a great influence on the change of reproduction hue. The amount of ink printed on the paper will affect the dot increase, and the dot increase will affect the printing contrast. When printing black or color halftone images, the increase of dot will change the picture contrast and cause the loss of image detail and clarity.Influence of Paper and Ink Characteristics On Dot Expansion

       In multi-color printing, dot increase will lead to contrast loss, dark image, dot paste and sharp color change. Before printing, we must select appropriate paper for printing, especially considering the factor of dot increase, we should be more careful in the selection of paper. The printability of paper depends on its surface characteristics. Influence of Paper and Ink Characteristics On Dot Expansion

      For example, the faster the transfer ink is accepted, the greater the dot increase of printed matter. Absorbency is a characteristic that determines the speed and amount of ink penetration into the paper. The better the absorption performance of the paper, the higher the percentage of dot increase. When the ink is fixed on the absorbent paper, it will penetrate and diffuse. The absorption speed of paper to ink plays a key role in the increase of dot. Influence of Paper and Ink Characteristics On Dot Expansion

      For example, when printing 300 line prints, do not use highly absorbent paper. The flatness of paper is the deviation between the actual surface of paper and the ideal plane. The relationship with dot increase is that the higher the paper flatness, the smaller the dot increase, and the lower the flatness, the more severe the dot increase. Influence of Paper and Ink Characteristics On Dot Expansion

      The smoothness of the paper is high, and the layout pictures and texts on the printed products can be reproduced truthfully, especially the small dots can be accurately restored. For the paper with low smoothness, due to the concave shape on the paper surface, it is easy to make the dot printing unclear and the printing layout level is not clear. Influence of Paper and Ink Characteristics On Dot Expansion

     The smoothness and thickness uniformity of paper will have a direct impact on the uniformity of printing pressure and ink color. Therefore, the use of pressure to achieve the production process of printing requires the more uniform the thickness of the paper, the better. Smoothness is also the guarantee of improving printing quality. However, the method to improve the smoothness of the paper is mainly to add fillers and calendering.Influence of Paper and Ink Characteristics On Dot Expansion

       In this way, the tightness of the paper is improved, and its elasticity and ink absorption are reduced, so the back of the printed matter is easy to rub and dirty. In addition, when the printing pressure is too high, it is easy to make the ink layer spread, imprint and dot increase and deform.Influence of Paper and Ink Characteristics On Dot Expansion 

      Based on these conditions, the paper with uneven smoothness and obvious difference in rough light should be classified and separated, so that when printing the paper with poor smoothness, the clear imprint can be obtained by appropriately increasing the printing pressure and ink amount, so as to improve the printing quality. The smooth surface of ink produces the best field density on high-quality paper.Influence of Paper and Ink Characteristics On Dot Expansion

       When the paper quality decreases, the field ink density decreases, resulting in a certain dot increase, which affects the quality of printed matter. Obviously, the absorbed ink cannot produce a smooth printing surface. Influence of Paper and Ink Characteristics On Dot Expansion

      The higher the number of wires, the smaller the dot diameter, and the small pits on the paper can also distort or omit small printing plate dots.Influence of Paper and Ink Characteristics On Dot Expansion

      Therefore, the higher the number of screen lines, the higher the smoothness of the paper is required, which is a principle of selecting paper. However, in practice, some properties of ink can also be adjusted appropriately or process parameters can be changed to adapt to the characteristics of paper. 

      There are many kinds of coated paper on the market, such as glossy coated paper and matte coated paper. Influence of Paper and Ink Characteristics On Dot Expansion

       Coated paper helps to improve the fidelity and color clarity of dot printing because its absorption is lower than that of non coated paper. As we all know, the dot gain of low absorbent paper is also small. Non coated paper has high absorption performance. The non coated paper with high absorption prints high screen line images. Influence of Paper and Ink Characteristics On Dot Expansion

      As a result, the dot increase percentage is very high. In theory, the dot increase of recycled paper is the same as that of base paper, but in fact it is larger than that of base paper. When the ink is transferred to the paper surface under pressure, due to the absorption of the paper, the ink diffuses around when penetrating, resulting in an increase in the dot, making the whole image darker. Obviously, for different quality paper, it will produce different dot enlargement effects. Influence of Paper and Ink Characteristics On Dot Expansion

        The stronger the paper absorption, the greater the dot increase value. Specifically, newsprint is the largest and coated paper is the smallest. The dot gain formed by paper performance generally shows the law of exponential expansion. In the process of prepress processing, the influence of dot gain must be compensated.Influence of Paper and Ink Characteristics On Dot Expansion

        For different sizes of dots, the dot increase value is different. Generally, the dot increase value of high-profile and dark tone is small, and the dot increase value of middle tone is large. It is generally recommended to use the default setting. For example, the default value for coated paper printing is about 17%, offset paper is about 22%, and newsprint is about 30%.Influence of Paper and Ink Characteristics On Dot Expansion