How to choose offset printing in printed matter
In terms of color, it is generally necessary to overprint several colors to get the color that the customer needs. For example, if the red color is copied by a four-color printing process, it must be overprinted by magenta ink and yellow ink. However, the results obtained by overprinting and trapping seem to be similar, such as black, gold, silver and other colors overprinting or trapping, the results are not very different; dark and hue similar to the light overprint The results obtained from trapping are similar.
Choosing overprinting or trapping in actual production requires comprehensive consideration of relevant issues and selection of appropriate processes.
From the point of view of registration and drying, it is considered that the overprinting will not cause whitening even if the overprinting is not accurate, but it is easy to cause the back surface to be dirty due to the too thick ink layer. The trapping is not easy to appear on the back side, but if the overprint is not allowed, it will be easy to whiten and affect the appearance.
For a monochrome machine, after the previous color is dried, it is printed after the color, which is good for the drying of the ink, but it is easy to use the overprint due to the inaccurate overprinting caused by the expansion and elongation of the paper.
For multi-color machines, multi-color printing is completed in an instant, and there is basically no problem that the paper absorbs water and elongates, resulting in inaccurate overprinting. The registration is improved, but the ink layer is deposited too thick in a wet overprint. It is prone to dryness, so it tends to use trapping.
Considering the color effect, when printing gold ink and silver ink on coated paper, the color obtained by printing full ink and silver ink on white paper in a trapping manner is thicker and purer than that printed on other ground colors. When printing black, if there is only a large-area solid image on the black plate, the ink amount of the black plate is increased by the trapping method, and the ink color printed on the white paper is thicker than the ink color obtained by overprinting on other solid ground colors. However, when printing only words and lines, because the human eye is not strong in distinguishing the density of thin lines, it is not necessary to print too small characters and lines, and the thin lines will be trapped. It is difficult to overprint.
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