The Color Theory of Printing Industry

Printing is an industry centered on color theory. In addition to the use of four-color inks in current prints, spot-color inks are also used at higher frequencies, especially in screen printing and gravure printing. Sometimes spot color inks can be printed by direct purchase, sometimes they need to be prepared with primary color inks for cost or special ink color requirements. In general, there are mainly two methods of blending inks. One is based on the basic data obtained by the ratio of instruments (such as densitometers) or chromatograms, and the other is that the operators of the machines directly rely on experience to perform the deployment. The latter method is currently more commonly used, but the experience requirements for printing operators are relatively high. How to grasp this technology quickly is the expectation of those who are involved in the printing industry.

Most of the vocational schools in the country that have set up printing professions have ink-transfer training courses to cultivate students' sense of color and master the techniques of ink deployment.

As an internship instructor for a vocational college, the author takes the first-line teaching experience of the ink-transfer training course and believes that the key to grasping the ink deployment is to grasp the three aspects of “fine”, “bo”, and “walk”. "Qing" and "Bo" are comprehensive professional theoretical knowledge of ink transfer. "Running" is to apply theoretical knowledge to practice through some practical operations. Below is a brief explanation.

1 "Preciseness": Highlighting the Theoretical Essence in Teaching Transferring Ink Training

Students must have studied the course of "Printing Colorology" before attending the training courses for ink transfer, which has a certain professional theoretical basis. Therefore, in the teaching of ink-transfer training, teachers should grasp key theories that are closely related to practical application and should be thoroughly explained.

1) The color theory of ink color mixing: subtractive color mixing

Y+M=R, Y+C=G, M+C=B, Y+M+C=BK

C, M, and Y are the three primary colors of the colorant and cannot be obtained by mixing other colorants. The inter-color refers to the color obtained by mixing two primary colors, and the typical inter-color is R, G, and B, and the color obtained by mixing two or more Y, M, and C colorants in different amounts. Complex color refers to the color of the three primary colors mixed. Complementary color means that if two colors are mixed, they are complementary colors if they are black. The most typical three pairs of complementary colors are Y-B, M-G, and C-R.

The spot color is usually used in packaging and printing. A spot color means that a certain color is not a four-color overprint, but a special printing plate must be prepared first, and colors should be specially prepared and printed out at one time. Its characteristics are: usually used in the occasion of high printing color requirements; through the use of spot color ink to expand the scope of color reproduction; some colors are not available through the four-color printing; the use of spot colors can also solve the problem of color overprint is not allowed. The deployment of spot color inks is a key and difficult point in the teaching of ink-transfer training. Practical training instructors must focus on explaining and linking spot-color inks to students.

Professional ink deployment method: see the color of the sample to judge, through the deployment of experience, you can also rely on the proportion of chromatography to deploy. However, the chromatogram indicates that the number of colors is limited, and the color in the chromatogram is affected by paper, ink and printing conditions. Over time, the physical and chemical properties of the ink paper will change, affecting the use value of the color.

2 "Bao": Refers to and quotes related theoretical knowledge

Since color science is the core of printing, it is possible to introduce the part of the theoretical course related to color performance in the teaching of ink-transfer training. Such as "printing materials" course of paper performance and color performance, ink adjustability of the impact of the agent, "printing process" by the density meter to calculate the ink color elements, color sequence arrangement of the ink And so on, let the ink-transfer training not only stay in the simple hands-on operation, truly connect theory with practice, apply what they learn.

Or we can use the experience in actual operation, the color rendering effect of different printability papers on the ink, the effect of various ink additives on the performance of the ink, the characteristics of the ink itself, the influence of the work environment in the workshop, and the arrangement of the printing color sequence. The relationship of the final color effects, etc. Of course, these take some time to accumulate.

3 "Line": guide students to practice and analyze and measure the color palette

Through the operation and training, master ink preparation methods and techniques, and has the ability to analyze and solve problems such as color chromatic aberration.

Chromaticity measurement is a colorimetric method for obtaining colorimetric information according to the principle of colorimetry. The instrument used for colorimetric measurement is a spectrophotometer. In the teaching process, color measurement is used to grasp the use of the spectrophotometer and analyze the measured data.

Common colorimetric measurements include Yxy, Lab, and color difference measurements.

In the Yxy measurement method, Y represents the brightness, x represents the number of reds, and y represents the number of greens. In the Lab measurement method, L represents the lightness, the a-axis is the red-green axis, and the b-axis is the yellow-blue axis.

Color Difference Measurement: Two colors appear to be different, then there is a color difference between the two colors, and the color difference is expressed as ΔE.

Chromatic aberration shows very visually the visual difference between the two colors. It can be seen that the smaller the difference value, the smaller the difference between the colors, and vice versa, the greater the two colors have the same appearance, the color difference ΔE=0. The visual perception of color difference is shown in Table 2.

4 Conclusion

The deployment of ink is a must-have skill for printing workers. As an internship instructor for a vocational and technical college, it is more responsible for good ink transfer training courses. Through the three-stage teaching of “fine”, “bo” and “walking”, students can better master the methods and techniques of ink transfer and color sample analysis, have good professional qualities, and lay a good foundation for future employment.