Four-color and spot color printing question and answer
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1. What is four-color printing?
The four-color printing process generally refers to a printing process in which various colors of a color original are reproduced by using yellow, magenta, cyan primary color inks and black ink.
2. What is spot color printing?
Spot color printing refers to the use of yellow, magenta, and blue. A printing process in which other colors of ink other than black ink are used to copy the original color. In the packaging and printing, a large-color background is often printed by a spot color printing process.
3. What product must use a four-color printing process?
Photographs taken in color photography that reflect the colorful variations of nature, painters' color works, or other images containing many different colors must be passed for technical reasons or for economic considerations. The electronic color separation machine or the color desktop system scans the color separation and then copies it using a four-color printing process.
4. What kind of products will use spot color printing?
The cover of a packaged product or a book is often composed of uniform color blocks of different colors or regular gradation blocks and characters. These color blocks and characters can be color-separated and then printed with four primary colors of ink, or can be assigned with a special color ink. Then, only one spot color ink is printed at the same color block. In the case of comprehensive consideration of improving print quality and saving the number of overprints, it is sometimes necessary to use spot color printing.
5. What is the difference in the color of the spot color printing block and the four color overprinting color blocks?
The inks prepared by the spot color printing are obtained according to the mixing principle of the color reduction method, and the color brightness is low and the saturation is high: the spot color of the ink color is usually printed in the field, and the amount of ink is appropriately increased. When the thickness of the ink layer of the printing plate is large, the sensitivity of the change of the thickness of the ink layer to the color change is lowered, so that it is easier to obtain a uniform and thick printing effect.
The color blocks printed by the four-color printing process are composed of a certain proportion of dots, and the thickness of the ink layer must be strictly controlled when printing the dots, which is easy to change due to the thickness of the ink layer and printing. A change in process conditions causes a change in color intensity. Changes in the degree of expansion of outlets. This causes a color change. Moreover, since the change of any color constituting the color block causes the color of the color block to change, the chance of unevenness of the ink color will be multiplied, so the color block printed by the four-color printing process is not easy to obtain the ink color. Uniform effect. If you can't use the multicolor machine to overprint the color of the color block at a time. It is also easy to cause color shift due to the difficulty in controlling the color of the semi-finished product. In addition, the four-color printing is a combination of the subtractive color absorption and the additive color mixing of the dots, and the color block has a high brightness and a low saturation. For the light color block, a four-color printing process is adopted, and the ink has a low coverage, and the ink color is dull and lacks a thick feeling. Due to the angle of the dot, it is inevitable that people will feel the existence of the pattern.
6. From the perspective of improving product quality, what kind of products are suitable for spot color printing?
When printing a large area of light-colored uniform color blocks, it is usually added to the original ink to add a spot color ink to perform the on-site printing, so that the ink layer is thicker, and it is easier to obtain a uniform color and a thick effect. If a four-color printing process is used, a low number of flat screen dots must be used. However, the low number of flat nets are easy to be caused by tiny sand particles or slight exhaustion during the printing process, resulting in small dots at individual parts, resulting in uneven ink color: it is easy to supply too much water due to the printing. The paper powder accumulates on the printing plate and the blanket, and the smoothness of the paper is low, which causes the ink transfer at the small dots to be poor. As a result, the ink becomes lighter and the ink is uneven.
For dark large-area color blocks, using a four-color printing process, it may be necessary to superimpose the high-salty dots of several colors, the ink layer is too thick and easy to appear back and dirty; and the spot color printing process requires only one printing. The color is not easy to appear dirty on the back. Using four-color printing process, some parts of the graphic may be synthesized by several colors; while the spot color printing process is used, only one color is printed in the corresponding part, which avoids the possibility of overprinting error.
7. From the perspective of economic efficiency, what kind of products are suitable for printing with spot colors?
From the perspective of economic efficiency, it is mainly concerned that the use of the spot color printing process can save the number of overprinting. Because reducing the number of overprints can save printing costs and save on pre-production costs.
8. Can a product use four-color printing and spot color printing at the same time?
If a product has a color-level picture and a large-area background color, the color-level picture portion can be printed in four colors, and the large-area background color can be printed in a spot color. The advantage of this is that the four-color printing part can correctly restore the picture by controlling the density of the ground, and the under-color part can obtain a uniform and thick visual effect by appropriately increasing the amount of ink. This method is often used in the printing production of high-end packaging products and stamps, but the cost of printing and plate making is also increased due to the increase in the number of colors.
9. When using a four-color printing process, if there is a large area of black solid, how to make the plate is more conducive to black solid color?
When using the four-color printing process, in order to ensure the correct restoration of the tone and color, the thickness of each color layer should be strictly controlled. Generally, in four-color printing, the black solid density does not exceed 1.8, and printing a large black area at such a density would lack a solid visual effect. A commonly used force method is to overprint about 40% of cyan in a large black solid part.
The black solid overlays a small amount of cyan, which is still black from the hue, but the visual effect is thicker. Originally printed on white paper only one color black, due to the paper hair during the printing process. Paper powder builds up on the blanket, or the transfer of ink is affected by other reasons, which will cause white sand on the black ground, and the black and white contrast is very conspicuous. If the cyan flat net is overprinted, even if there are a small amount of sand holes on the black ground, since the exposed paper base is no longer a white paper, but the cyan dot, the black-green contrast is less conspicuous than the black-and-white contrast. Make the black background look more even and beautiful.