Usually color photography photos, color art works and other pictures containing many different colors, due to process requirements or economic considerations, must be scanned and separated by a color desktop system, and then a four-color printing process is used. Copy is complete.
The covers of packaging products or books are often composed of uniform color blocks of different colors or regular gradient color blocks and text. These color blocks and text can be overprinted with three primary color inks and black ink after color separation. Distribute spot color inks, and then print only one spot color ink on the same color block.
Although both four-color printing and spot color printing can print uniform color blocks, in the case of comprehensive consideration of improving printing quality and saving the number of overprints, spot color printing is sometimes used, because when using spot color printing color blocks, you can pass Properly increase the amount of ink to achieve the printing effect.When the thickness of the ink layer on the layout is large, the change of the ink layer thickness will be less sensitive to color changes, so it is easier to obtain a uniform and thick printing effect; instead of using four-color overprinting Printing is easy to change the color intensity due to changes in the thickness of the ink layer and changes in the printing process conditions, and any change in the color of the color block will cause the color of the color block to change, resulting in the chance of uneven ink color. Therefore, it is not easy to achieve the uniform ink color effect with the color block printed by the four-color printing process.
Whether to use four-color printing or spot-color printing, we need to consider whether the spot-color printing process can save the number of overprints, because reducing the number of overprints can not only save printing costs, but also save the cost of pre-press production. There are also occasions where both four-color printing and spot-color printing are used on the same printed matter. For example, if the screen of a certain product has both color gradation screen and large area background color, the color gradation screen part can be printed in four colors, and the large area background color can be printed in spot color.
The advantage of this is that the four-color printing part can make the picture correctly restored by controlling the solid density, and the background color part can obtain a uniform and thick visual effect by appropriately increasing the ink volume. This method is often used in the printing and production of high-end packaging products such as cigarette packets, wine labels and stamps, but the increase in color number also increases the cost of printing plate making.
