(I) influence of printing ink layer thickness and viscosity on printing ink color

      Proper printing ink layer is an important measure to ensure the quality of printing ink and prevent printing from sticking and dirty. If the ink layer is too thick, its viscosity is bound to increase, which is easy to produce paper wool and affect the uniformity of ink color of printing. If the printing ink layer is too thin and the ink viscosity is insufficient, the printed ink will be too light and the visual effect of printing will be poor. With the extension of printing machine rotation time or the acceleration of printing speed, the friction coefficient increases, and the ink temperature will gradually increase. Direct Influencing Factors Of Printing Ink Color

      Therefore, the ink will become thinner and its viscosity will decrease accordingly. Therefore, these situations must be comprehensively considered when adjusting ink to ensure that batch products obtain relatively balanced printing ink color. However, in the actual production process, the decline of ink viscosity is inevitable. The ink color of the printed products is thick at the beginning of printing and becomes lighter later. Direct Influencing Factors Of Printing Ink Color

      The ink supply can be increased by appropriately adjusting the rotation angle of the ink transfer iron roller to keep the consistency of the ink color before and after. In addition, in order to prevent excessive variation of ink viscosity from affecting the balance of ink color of printed products, the contact between each rubber roller and ink string iron roller shall not be too tight, and the colloid shall not be too hard, so as to minimize the friction heat and maintain the appropriate concentration of ink.Direct Influencing Factors Of Printing Ink Color

（2） Influence of printing pressure on ink color of printing

      Printing pressure is one of the important conditions to realize imprint transfer. Because the printing plate surface is not absolutely flat, there are inevitably subtle concave convex and uneven thickness on the paper surface. If the printing pressure is insufficient or uneven, the printing ink color on the plate will be uneven. Direct Influencing Factors Of Printing Ink Color

      Therefore, the ideal printing process is based on the “three leveling” (that is, the printing plate is relatively flat with the inking roller and the lining body to obtain good contact conditions), and a thinner ink layer can obtain a more uniform ink color on the print through the action of balanced printing pressure. If the printing pressure is insufficient or uneven, there is poor contact between the lining body and the printing plate surface. Increasing the ink delivery can meet the visual effect of the printing plate ink color, but it is not desirable to not only increase the ink consumption, but also prone to printing sticking.Direct Influencing Factors Of Printing Ink Color.Direct Influencing Factors Of Printing Ink Color

（3） Influence of cot quality on printing and ink color

      In terms of embossing and flat printing process, whether the printing can obtain the ideal ink color is closely related to the quality of cots. There are three kinds of equipment for printing color printed matter, including ink transfer roller, ink leveling roller and inking roller. 

     There are five or six, or even more than 10, of which the ink transfer roller and inking roller have a great impact on the shade of ink. The quality of COTS is mainly reflected in elasticity, viscosity, center of circle and surface finish, and the viscosity mainly affects the intensity of ink. In the printing process, only when the cot maintains a certain viscosity can it ensure that the amount of ink coated on the plate is uniform in each printing cycle. However, in the actual production process, the viscosity of COTS is not stable.Direct Influencing Factors Of Printing Ink Color

       First, the increase of paper dust in ink affects the viscosity of colloid; Secondly, the viscosity enhancer (i.e. glycerol) on the colloidal surface is lost with the increase of temperature and service time. The viscosity of the cot surface gradually decreases, and the ink absorption performance decreases accordingly, which affects the balance of ink color of printing. Therefore, polyurethane Cots with stable quality should be used for printing plate products. If bulk products are printed, the cots shall be cleaned in time.Direct Influencing Factors Of Printing Ink Color

（4） Influence of paper cleanliness difference on printing ink color

      In fact, the relationship between paper and ink is complex. If you only consider the ink color of a book, you should note that the smoothness of the paper surface has a certain relationship with the ink color. If the pressure of each version is the same, the smoothness of the paper surface is inversely proportional to the ink consumption, and the ink absorption of smooth fans is small, on the contrary, the ink absorption is large.Direct Influencing Factors Of Printing Ink Color 

      Therefore, if there is a difference in the smoothness of the front and back surfaces of the paper, the method of increasing the ink volume and pressure should be adopted as appropriate to make appropriate adjustment. It is customary to print the smooth surface first and then the rough surface. When printing, the amount of ink shall be increased appropriately to achieve good printing effect. BR>Direct Influencing Factors Of Printing Ink Color

（5） Influence of light change on printing ink color

      Generally, there are three light sources to identify the ink color of printing: sunlight, fluorescent lamp and electric lamp. The three light sources have different luminous conditions, and the color of the emitted light is also different. The vision is pure white light, the fluorescent lamp is white with blue, while the electric lamp is red and slightly yellow. Although the light sources of daylight and fluorescent lamps are somewhat similar, the differences between them should be taken into account when identifying high-quality products. 

      The influence of light on the identification of ink color is not only the light source, but also related to the intensity of light and irradiation angle. Under the same light source, the intensity of the reflected light on the illuminated sheet is mainly determined by the distance between the sample sheet and the light source, the near is strong and the far is weak. The correct irradiation angle should be that the incident angle is equal to the reflection angle. Direct Influencing Factors Of Printing Ink Color

     Light irradiation on the sample inevitably has partial refraction, but it has little effect on the identification of ink color. When identifying the ink color of printed matter, whether during the day or at night, it should be carried out under the condition that the intensity of light source and irradiation angle are the same, so as to prevent color deviation or variation of ink color caused by ink mixing error.Direct Influencing Factors Of Printing Ink Color

（6） Influence of overprint inaccuracy on ink color

      Whether the overprint of various color printing plates is accurate or not will have a great impact on the printing hue. Overprint accurate hue effect is also good, overprint inaccurate printing hue will be deviated. This is due to the position difference of overprint of various color dots, which will inevitably produce visual color difference. Therefore, overprinting must be accurate to ensure that printing hue meets process requirements. Direct Influencing Factors Of Printing Ink Color

      In order to prevent the color deviation caused by inaccurate overprint caused by paper expansion and variation, multi-color machine should be used to complete color stacking printing at one time for dot color products with high quality requirements, so as to improve the overprint quality. In addition, the paper shall be hung and dried to reduce the variation of printing sheets in the printing process.Direct Influencing Factors Of Printing Ink Color