Spot color printing in Book Printing
11-02-2021 18:12:20

Spot color is different from the color of CMYK. It refers to a color not synthesized by printing CMYK, but printed with a specific ink pre mixed by the printing factory or produced by the ink factory. For each spot color of printed matter, there is a special color plate corresponding to it during printing.


Use spot color can make the color more accurate. Although the book printing color cannot be accurately represented on the computer, the accurate color of the color on the paper can be seen through the preprint color sample card of the standard color matching system.


Ink printing color, there are generally two methods


(1) Printing color using four-color ink


The mixed printing ink modulates the spot color, that is, spot color printing is used, and the color is expressed by solid color or dot. The color assignment and plate making methods of the two methods are different in printing design.


Spot color printing process is often used to print large area background color in packaging printing. The covers of packaged products or books and periodicals are often composed of uniform color blocks of different colors or regular gradual color blocks and characters. These color blocks and characters can be separated and overprinted with four primary colors of ink, or spot color ink can be prepared, and then only one kind of special color ink can be printed at the same color block.


Under the condition of comprehensively considering improving book printing quality and saving overprint times, spot color printing is sometimes selected. The ink prepared by spot color printing obtains the color according to the mixing principle of pigment subtraction method. Its color lightness is low and its saturation is high. Compared with four-color printing, it is easier to obtain the printing effect of uniform and thick ink.


For the color block printed by four-color printing process, because most of the colors constituting the color block are composed of a certain proportion of dots, when printing dots, the change of ink layer thickness and the change of printing process conditions can cause the change of color intensity and dot expansion, resulting in the change of color. Therefore, the color block overprinted by four-color printing process is not easy to achieve the effect of uniform ink color.


The cost of spot color should be considered from the perspective of economic benefits, mainly to see whether the spot color printing process can save the number of overprint. Because reducing the number of overprint can not only save the printing cost, but also save the cost of prepress production. General spot color printing is usually used for printing below three colors. If more than four colors are required, CMYK four-color printing is appropriate in terms of cost.


In addition, if there are already four printing colors in the same layout, it is equal to one more color for printing. If the printer does not have redundant printing units (such as less than four-color printer or four-color printer), it will take twice the time to finish the book printing, and the cost will be higher.


If there is both a color hierarchical picture and a large-area background color in one picture, the color hierarchical picture part can be printed in four colors, and the large-area background color can be printed in spot color. In this way, we paid a slightly higher cost, but obtained high-quality products. Because the four-color printing part can correctly restore the picture by controlling the field density, and the bottom color part can obtain the visual effect of uniform and thick ink color by appropriately increasing the amount of ink.

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