Four-color and spot color printing

1. What is four-color printing?

The four-color printing process generally refers to a printing process in which colors of yellow, magenta, and cyan inks and black ink are used to reproduce various colors of a color document.

2. What is spot color printing?

Spot color printing refers to yellow, magenta, and cyan. A process for copying the color of a document by using a color ink other than the four-color ink of black ink. In the packaging printing, spot color printing is often used to print a large area of ​​background color.

3. What product must use four-color printing process?

Photographs taken in color photography that reflect the colorful changes in the natural world, painters' color works, or other images containing many different colors must be processed for technical or economic considerations. The electronic color separation machine or the color desktop system scans the color separation and then uses a four-color printing process to complete the replication.

4. What kind of product will use spot color printing?

The cover of a packaged product or book is often composed of uniform color patches of different colors or regular gradient patches and texts. These patches and texts can be color-coded and printed using four-color inks. Spot inks can also be dispensed. , and then only print one spot color ink at the same color block. In consideration of improving printing quality and saving the number of overprints, spot color printing is sometimes used.

5. What is the difference in the visual effect of the color of a spot-color printing block and a four-color printing block?

The inks that are prepared by spot color printing are obtained according to the subtractive color mixing principle of color materials, and have lower color brightness and higher saturation: the uniform color blocks of ink are usually printed in the field and the ink volume is appropriately increased. When the thickness of the ink layer on the layout is large, the sensitivity of the change in the thickness of the ink layer to the color change is reduced, so it is easier to obtain a uniform and thick printing effect of the ink.

The use of four-color printing process overprint color blocks, due to the composition of the color of the various colors are mostly composed of a certain percentage of dots, when printing dots, the ink layer thickness must be strictly controlled, easy to change due to the ink layer thickness and printing Changes in process conditions cause color intensity changes. Changes in the extent of outlet expansion. This leads to a change in color. Furthermore, since any color change that composes the color block will cause the color of the color block to change, and the chance of uneven ink will multiply, the color blocks overprinted by the four-color printing process are not easy to obtain ink color. Uniform effect. If you can not use multi-color machine once overprint the color of the color block. It is also prone to color shifts due to the inability of the color of the semifinished product to be controlled. In addition, the four-color printing results in the combined effect of subtractive color absorption and additive color mixing of the dots, and the color block has higher brightness and lower saturation. For light-colored blocks, a four-color printing process is used. Due to the low coverage of the ink by the ink, the ink has a lack of a solid feel. Because of the network point of view, it will inevitably make people feel the presence of patterns.

6. From the perspective of improving product quality, what kind of product is suitable for spot color printing?

In the printing of a large area of ​​light-colored uniform color blocks, usually added in the original ink: medium light agent to match the spot color ink, and then field printing, so that the ink layer is thicker, easier to get uniform color, thick effect. If you use a four-color printing process, you must use a low number of flat screen dots. However, the low-grade flat screen outlets are liable to be caused by slight sand particles or slightly poor suction resulting in small dots in individual parts during the printing process, resulting in uneven inks: the printed sheets are prone to excessive water supply. Paper powder accumulates on plates and blankets, and paper smoothness is low, which causes poor dot transfer of ink. As a result, the ink becomes lighter and the ink is uneven.

For dark, large-area color patches, a four-color printing process may require superposition of several colors of high-salty dots. The ink layer is too thick to be easily stained on the back. For a spot-color printing process, only one is required. The color is not easy to appear dirty on the back. With the four-color printing process, some parts of the graphic and text may be synthesized by several colors. With the spot-color printing technology, only one color is printed on the corresponding parts, avoiding the possibility of overprinting errors.

7. From the perspective of economic efficiency, what kind of product is suitable for printing with spot colors?

From the economical point of view, it is mainly to see if the spot color printing process can save the number of overprints. Because reducing the number of printing can not only save printing costs, but also can save the cost of prepress production.

8. Can a product use four-color printing and spot color printing at the same time?

If a product has both a color-graded picture and a large-area background, the color-graded picture part can be printed in four colors, and the large-area background color can be printed in spot colors. The advantage of this method is that the four-color printing part can correctly restore the picture by controlling the solid density, and the under color part can obtain a uniform and thick ink visual effect by appropriately increasing the ink volume. This method is often used in the production of high-end packaging products and stamps, but the increase in the number of colors also increases the cost of printing plates.

9. When using a four-color printing process, if there is a large area of ​​black solid, how to make the plate more conducive to black solid ink thick?

When using the four-color printing process, the thickness of each ink layer should be strictly controlled in order to ensure the correct reproduction of the tone and color. Usually in four-color printing, the density of black solids does not exceed 1.8. Printing large areas of black solids at such densities will result in a lack of solid visual effects. The commonly used force method is to overprint about 40% of cyan in a large area of ​​black solid parts.
A small amount of cyan is overprinted in black on the ground, and it is still black when viewed from the hue, but the visual effect will be thicker. Originally printed on a single piece of paper only black, due to the paper hair during printing. Paper powder accumulates on the blanket, or affects ink transfer due to other reasons, causing white sand eyes to appear on the black surface, and the black and white contrast is very conspicuous. If the cyan flat screen is overprinted, even if there are tiny blisters on the black ground, since the exposed white paper base is no longer a blue one, the black and blue contrast is not so conspicuous compared to the black and white contrast. Makes the black background look more even and beautiful.