Reasonable arrangement of overprinting sequence is the key

In color printing, how to arrange colors sequentially is an important issue for process technicians. An important role of printing is to copy the manuscript artistically. This requires the printer to have a certain level of artistic appreciation and ability to grasp the changes in color. Improper arrangement of the color sequence may lead to color deviations, color mixing, and reverse overprinting of the printed matter; the scientific arrangement of the color sequence will make the color of the printed matter closer to the original, and even strengthen a certain color atmosphere, so that the level is clear, the outlets are clear, and overprinting is accurate. The colors are real, natural, and coordinated.

There are three reasons that cause the color sequence to be arranged: the effect of overprinting of the ink and the disadvantage of the ink color material itself, the quality of the paper, and the ability of the human eye to recognize the color. The most fundamental reason is the incomplete transparency of the printing ink itself, that is, the hiding power of the ink itself. After printing, the ink has a certain hiding effect on the ink layer that is printed first, resulting in the color of the printed product is always emphasized on the performance of the latter color, or it is emphasized on the mixed color of the rear color and the front color. The starting point of choosing the color sequence is to take care of the main aspects (such as tone reproduction, color reproduction, graphic clarity, printing uniformity and print repetition rate, etc.) according to the specific conditions of the manuscript, combined with the current process conditions, and flexibly arrange the color sequence. .

1. Due to the good transparency of yellow ink, the last color is favorable for sufficient white light to enter into the upper and lower ink layers to obtain bright and vivid colors.

2. Yellow ink has a faster drying performance and has a larger printing area. The listing of yellow ink to the last color not only prevents the vitrification caused by the fast drying speed of yellow ink, but also makes use of its large printing area and the ability to quickly oxidize the conjunctiva, covering the surface of other ink layers, making Prints have a certain degree of gloss.

3. The yellow color is in the last color, which is convenient for controlling the amount of yellow ink used, and can be adjusted against the original at any time.

4. Yellow ink is expensive and it can save the amount of yellow ink and reduce costs.

Color printing is a combination of technology and art. When we arrange printing color sequence, we appropriately consider it from an artistic point of view, can make the printed matter more artistically appealing and satisfy readers' needs.

The first color and the second color of the offset printing monochrome machine are printed at intervals. During this time, the linking material in the oil foam gradually penetrates the paper, and the surface layer of the ink gradually oxidizes the conjunctiva. When the second color is printed, the ink is printed on the conjuncted ink layer, which is called wet-press drying. Multi-color printing machine at the time of printing each color version of the ink superimposed in less than a few seconds together, the interval between the colors is very short, the latter printing color is not printed on the oxidized conjunctiva layer of ink This is the so-called Wet pressing wet.

Multi-color machine in the process of "wet pressure wet", the white paper is the most vulnerable to the first set of ink. Black is the most obvious, followed by cyan and magenta. It is called the three strong colors. The human vision is the slowest to reflect on yellow, so it is placed last. The ink of the first color group should be thicker, and the concentration of the various color inks afterwards is gradually reduced. The black color is printed on the first color to facilitate overprinting accurately. This is why multicolor machines are mainly based on black, cyan, magenta, and yellow. (In general, the four-color ink viscosity relationship: T black ≥ T blue = T red> T yellow. T represents the viscosity of the ink)

The overprinting of multicolor ink is performed under the condition of “wet to wet”. In the relationship between ink viscosity and overprinting, the viscosity of the after ink cannot be too much larger than the previous color ink, otherwise it will be printed. The ink of the previous color sticks down and is transferred to the printing plate by the rubber roller, which not only causes the “color mixing” of the ink, but also causes the ink not to be printed on. The ink of the printing piece is very light and not spirited. Found that this situation can take to adjust the viscosity of the four-color ink or change the order of the ink to remedy the method. (Adjust viscosity of the ink by adding a viscosity-reducing agent such as mineral oil or adding some tackifiers such as zero varnish.)

Arrangement The color sequential method should follow the principle of highlighting the dominant color to prevent the main color from being covered to determine the color sequence. In general, the color area is based on the screen area and the dominant color.

Therefore, after accepting product printing orders, we must analyze the focus of a certain color of the sample draft screen, change the color sequence to meet the original, to fully express the original, and better reproduce the tone and color.

The portrait-oriented pictures (warm tones) of the general portrait calendar are dominated by black, blue, red, and yellow. In general, large-scale landscape-dominated pictures (cold) are mainly black, red, blue, and yellow. The large-area four-color stacked spot color should be dominated by the dominant color, which includes a large area of ​​black, and does not rule out the possibility of the final printing sequence. For some of the different shades of the main color version in the case of printing and proofing the gap between the more difficult circumstances can be used to fold the sub-version of the printing method or multi-exposure PS printing method. In short to restore the main color. Be bold and science. It is necessary to fully understand that plate-making proofing is round-pressing and printing is round-pressing. The fact that dot gain value printing is greater than proofing.

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