Printing Color Classroom: Variables for Printing Ink Colors

Referring to the variables affecting the color of gravure ink, the industry will first point out that the fineness of the mesh on the mesh drum affects the color, and the answer is basically correct but not complete. In principle, mesh fineness does affect the color, but generally gravure printing technicians will take this into account. In fact, in addition to the fineness of the Internet, another factor that has been forgotten is often overlooked. In gravure printing, the viscosity of the ink is often ignored by the print technician and the viscosity is seriously ignored when formulating the formulation. Even ink suppliers and printers can cause ink color errors due to viscosity.

The high and low viscosity of the printing gravure ink is related to the printing speed. In general, the faster the printing speed, the lower the viscosity of the ink will be in order to match the high-speed operation of the printing press. The author once visited an intaglio printing factory. Their technicians told me something that was eerie to me. He said that before the press operator went near work, they would speed up the printing process in order to finish the work on the handle quickly. Add a lot of solvent in the ink to reduce the degree of draft, with the press operation. This can indeed increase the printing efficiency, but the color of the printed matter is not guaranteed. Adding a large amount of solvent to reduce the viscosity will make the printed material lighter in color, ie its printing density or concentration will be lower than normal. Because when a large amount of solvent is added to the ink, the concentration of pigment in the ink (the number of ink pigments per cubic meter) will decrease in real time. Printing on the same mesh cylinder will naturally reduce the number of ink pigments per square centimeter of the color of the printed material. The density or concentration drops rapidly or the color fades. Basically gravure ink formulations must be adjusted for different printing environment conditions, including printing speed, ink viscosity, and mesh fineness.

General gravure ink factory after production of gravure ink, when shipped will take into account the stability of the ink and transportation costs, the ink did not add the appropriate solvent at the factory, that is, the ink is delivered to the customer with high concentration and high viscosity state. When the printing plant receives the ink, because the ink concentration and viscosity are too high, the printer's technician will add the solvent by itself until the viscosity of the ink drops to a suitable printing environment. This process will stretch two issues. First, technicians judge the viscosity of inks according to their criteria. Most technicians do not use viscosity cups to measure the viscosity. They all use ink sticks or sticks to stir the ink, and then the ink knife or stick is connected to the ink. Pull, and then feel the viscosity of the ink, so the viscosity of the ink changes at least one to three seconds is impossible to detect. If the gravure ink viscosity differs by two seconds, the entire printing color will also change. On the other hand, the quality and concentration of the solvent used by the printing plant may also be different from that of the ink factory. Therefore, the color of the gravure ink may also be changed on the raw materials. When the ink factory deploys the ink, only the use of its own solvent is generally considered. In fact, the printing factory can use the ink factory's raw materials, coupled with the use of some of the standard viscosity testing equipment, such as viscosity cups. It is also necessary to inform the ink factory of the viscosity at the time of printing, so that the ink factory can adjust the formula.

In addition to the viscosity of gravure ink, printers will ignore the problem of whitening. Especially in the plastic packaging printing, since the gravure ink is printed on the plastic film, its color is often transparent, so the color is more easily affected by the background. Therefore, in the printing process, a layer of white ink is often added to the ink printed with color as the bottom, that is, the cover is white. The main reason is to increase the hiding power of the entire ink, so that the color is opaque and appears in the same state. To avoid the color deviation caused by the background color. This layer of white ink has affected the overall color, the situation is like the lithography, the color of the paper will affect the color of the print and its ink formula, that is, white ink used as a set of white like white paper, so the color must be clear before the set The white color of white ink in order to adjust the formula.

More attention should be paid to the environmental conditions such as printing speed, ink viscosity, mesh fineness, and tray whitening. It is not only necessary to consider the use of computer color matching, but even manual color matching should also be taken into account. Therefore, it is very difficult to manually adjust the color composition of gravure ink. . In the manual deployment, color often appears, but the viscosity is not controlled to match the speed of the printing press. Finally, the solvent is added to adjust the viscosity, which makes the printing color lighter. Therefore, as long as the computer color matching system can input the relevant environmental conditions such as ink viscosity, mesh fineness, and white support in advance to the computer, the computer can calculate the appropriate recipe. This formula can not only prepare accurate colors according to different mesh fineness and printing speed, but also control ink viscosity.