How to make the order of overprinting orderly
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In color printing, how to properly arrange the order of color printing is an important topic for process technicians. An important role of printing is to copy the manuscript artistically, which requires the printer to have a certain artistic appreciation and ability to master the color change. Improper arrangement of color sequence may lead to color shift, color mixing and reverse overprinting of printed matter; scientific arrangement of color sequence will make the printed matter closer to the original, and even strengthen a certain color atmosphere, so that the level is clear, the dots are clear, and the overprint is accurate. The colors are real, natural and harmonious.
There are three reasons for the arrangement of the color sequence: the influence of the ink overprinting and the shortcomings of the ink color itself, the quality of the paper, and the ability of the human eye to recognize the color. The most fundamental reason for this is the incomplete transparency of the printing ink itself, that is, the hiding power of the ink itself. The ink printed on the back has a certain covering effect on the ink layer which is printed first, so that the color of the printed matter always emphasizes the performance of the latter color, or the mixed color of the back color and the front color. The starting point for selecting the color sequence is to arrange the color sequence according to the specific conditions of the original, combined with the current process conditions, taking care of the main aspects (such as tone reproduction, color reproduction, graphic definition, printing uniformity and printing repetition rate). .
1. Since the yellow ink has good transparency, the last color is used to facilitate sufficient white light to enter the upper and lower ink layers to obtain bright and vivid colors.
2. Yellow ink has a faster drying performance and a larger printing area. The yellow ink is listed in the last color, which not only prevents the vitrification caused by the excessive drying speed of the yellow ink, but also utilizes the characteristics that the printing area is large and the conjunctiva is quickly oxidized, and the cover is covered on the surface of other ink layers. The print has a certain degree of gloss.
3. The yellow color is in the last color, which is convenient for controlling the amount of ink used in yellow, and can be adjusted at any time as it is.
4. Yellow ink is expensive, and the last color can save the amount of yellow ink and reduce the cost.
Color printing is a combination of technology and art. When we arrange the printing color sequence, proper consideration from the artistic point of view can make the printed matter more artistic and appealing to the readers' needs.
There is an interval between the first color and the second color of the offset printing machine. During this time, the binder in the oil gradually penetrates into the paper, and the surface of the ink gradually oxidizes the film. When the second color is printed, the ink is printed on the ink layer of the conjunctiva, which is called wet pressing. In the multi-color machine, the inks of the various color plates are overprinted together in less than a few seconds, and the interval between the colors is extremely short, and the post-printing color cannot be printed on the ink layer of the oxidized conjunctiva. Wet and damp.
Multi-color machine In the "wet pressure and wet" process, white paper is the most acceptable for the first set of ink. The black is the most obvious, followed by the blue and magenta, which are called the three strong colors. The human vision is the slowest to reflect the yellow, so it is placed at the end. The first color group ink should be thicker, and the concentration of each color ink will be decremented step by step, and the black color is printed in the first color to facilitate accurate overprinting. This is why multicolor machines generally use black, cyan, magenta, and yellow as the main color sequence. (General 4 color ink viscosity relationship: T black ≥ T blue = T red > T yellow. T represents the ink viscosity value)
Multi-color machine ink overprinting is carried out in the case of "wet to wet". In the relationship between ink viscosity and overprinting, the tack value of the back color ink should not be too much larger than the previous color ink, otherwise it will just be printed. The former color ink sticks and is transferred from the rubber roller to the printing plate, which not only causes the "mixing color" of the ink, but also causes the ink to not be printed, and the ink color of the printing is very light and not spirited. It has been found that this can be remedy by adjusting the viscosity relationship of the four-color ink or changing the order of the inks. (Adjust the viscosity of the ink by adding a viscosity reducing agent such as mineral oil or adding some tackifier such as No. 0 varnish.)
The arrangement of the color sequence method should follow the principle of highlighting the main color of the picture to prevent the main color from being covered to determine the color sequence. In general, the screen area and the dominant color are used as the basis for color order.
Therefore, after accepting the product printing list, it is necessary to analyze the focus surface of a certain color of the proof sheet image, appropriately change the color sequence to satisfy the original, to fully express the original, and better reproduce the tone and color.
The general portrait-like character-oriented picture (warm tone) is dominated by black, blue, red, and yellow. Generally, the large-scale landscape-oriented picture (cold tone) is mainly black, red, blue, and yellow. The spot color of a large area of 4 colors should be based on the dominant color, including large areas of black, and the possibility of the final printing color sequence is not excluded. For some of the main color versions of different shades, it is possible to use a two-step printing method of multi-level folding or a multi-exposure printing PS version method in the case where the printing and proofing comparisons are difficult. In short, it is necessary to restore the spot color. Be bold and be more scientific. It is necessary to fully understand that the plate proofing is round and flat, and the printing is round and round. The dot enlargement value is printed more than the proof.