Spot ink preparation

Printing can be used to print colorful prints by using tricolor inks (yellow, magenta, cyan) and black inks, but some product colors can hardly achieve the effect of thick and bright colors through common composite dots, or from the process and cost. Considering that it is not necessary to perform separation or multi-color printing, monochrome can print special color effects required by the original color sample. This requires the printing of spot color inks, such as the printing of large-area solid blue on the Speedpost envelope, because the requirements The color is bright and thick, it is difficult to achieve the color effect of the manuscript with four-color printing, it requires spot color blue printing, in addition, some books and magazine covers, envelopes and letterhead micro-standards, etc., because of high quality requirements (thick field), the number of production Small, short time, low cost, only use color ink printing without separation, to meet the requirements of users.

Ink manufacturers cannot and do not need to produce various hue inks. They only produce several commonly used inks (such as four-color ink, gold red, big red, and mid-blue, etc.). For printers, there are " It is necessary to provide two or more original inks according to the user's original color sample to obtain a new hue ink. This process is the deployment of spot inks.

In production, there is currently no simple, highly-operational color analysis and testing instrumentation equipment. Basically, the experience of the ink-transferring personnel is the main reason. Because the ink-adjusting personnel do not grasp the spot-ink ink deployment technology well, it often causes a good adjustment. The improper ink quality or the ink on the machine did not find the hue is correct and redeployment, resulting in quality accidents, ink waste, workers repeatedly, time delays and other unnecessary trouble, which requires us to fully understand the spot color ink deployment technology And grasp.

Spot color ink mixing principle and spot color ink principle

The deployment of spot color inks is based on the color of the original and is based on the principle of subtractive coloration of the three primary colors of ink. The physical effect exhibited by the ink's pigment is called subtractive, which means that when the pigment shows a certain color, it means that the pigment selectively absorbs various colors in the white light spectrum (minus the color light).

The color change law of ink tricolor subtractive method is as follows:
Magenta+Yellow=Red Magenta+Cyan=Purple Cyan+Yellow=Green Magenta+Cyan+Yellow=Black So the mixing of the ink pigments is a weakening of the light green, which is a phenomenon of color reduction. The more pigments are mixed, the final color is The darker and nearer black.

The color rendering principle of spot color inks is that the ink pigments exhibit effects through the principle of subtractive color. For example, when the yellow and blue inks are formulated in the same amount, since the pigment in the printing ink is the main body of the ink coloring, the particles are very small and the insoluble suspension is 0.01-0.5um in diameter. We will print the prepared ink on paper and To make a partial enlargement, when the white light is illuminated, there may be three cases. I: When the white light is irradiated on the yellow ink particles, it absorbs the blue light, reflects the red light and the green light; II: When it is irradiated on the blue ink particles, it Red light is absorbed, green light and blue light are reflected; III: When irradiated on yellow and blue mixed ink particles, it absorbs red and blue light and reflects green light.

Due to the equal blending of yellow and blue ink, the chances of II and III are equal and the reflected light is as follows:
I: W-B-R=G
II: W-B=G+R
III: W-R=B+G
The reflected light combination effect is:
3W-(2B+2R)=3G+R+S=W+2G

Therefore, the color of these two inks after blending is green. If the yellow ink and the blue ink are not equal blends, then the II and III conditions are unlikely to be equal, and the yellow ink will make the ink yellowish, and vice versa. After grasping the law of the color change of the three primary colors, it is possible to draw inferences about the colors of various manuscripts.

How to mix spot color inks

For the deployment of spot color inks, the ink transfer personnel should make three preparations: 1. Hue deployment is accurate, in line with the original color standard; 2. Formulation ink printing accuracy is accurate; 3. The number of spot color inks is accurate.

Hue deployment accuracy

1. The ink transfer personnel should have a deep impression on the colors of the various inks produced by the ink factory, and have a keen sense. Ink transfer personnel need to have a good understanding of the three properties (hue, lightness, saturation) of various inks, and the color matching can be adjusted to the spot color ink of the spot color in the quickest time and with the least amount of original colors. The three parameters of hue, lightness and saturation are used to study its properties and serve as a basis for measuring the difference between two colors. Using it to express the description color can obtain a uniform color language, which is suitable for the needs of normalization and dataization.

2. A. Determine the primary and secondary color inks for the original color sample. The deployment of spot color inks is the key to the analysis of the original color samples after we master the color regularity and characteristics of several common inks. It is related to the accuracy of the entire ink hue. We can use the subtractive color method to analyze the hue of the original. The principle to be considered is to analyze the content of the original color sample in the three primary colors by the three primary color theory to determine the ratio of the primary color and the secondary color. Generally, one primary color is the primary color, and other colors are secondary colors.

When preparing China Telecommunications Corporation's standard color Telecommunications Blue, by observing it gives us the impression that the blue-based color is slightly red, and the entire ink is bright and thick, pure, that is, the brightness, saturation, and hue of the ink are pure, so we The use of sky blue, supplemented by bright, violet purple ink, although the color separation on the proofs ratio, but it is electronic color separation or color matching on the desktop system is not compatible with the actual printing ink.

Formulating China Mobile's mobile blue, because its standard color is printed on the printing press, it will have obvious color cast, increase the gray scale, giving people the feeling of staleness and darkness, so we can't stop at the difference between it and telecommunication blue. Few color separation ratios, but the use of hue is not pure, the darkness of the dark blue in the main color, and red, and then a little black ink to increase the gray scale of the entire ink.

b. Obtaining the ratio of the main and auxiliary color inks After we determine the main and auxiliary colors, the main and auxiliary color mixing ratios are mainly obtained through the following ways: according to past experience, the right proportion is obtained; according to the similar color samples in the inking manual Than; with a small amount of original ink to adjust the sample to get the correct ratio.

c. Match the color of the spot color ink with the original color sample. Use paper (usually coated paper, offset paper). Draw a small amount of spot color ink and use the “scrape method” or “topography” to obtain the ink. The sample is compared with the original color sample to adjust the ratio when there is a difference.

Precautions for color matching:

The light source for color recognition is the ideal uniform white light, the natural light toward the north window, and the artificial light source similar to the natural light, such as the fluorescent lamp and the incandescent lamp mixed with the light source;

- The ink color sample prepared is darker than the original color sample. Because the offset ink is mixed with the fountain solution and the ink is dried, the ink hue will become lighter. Also has the correct hue, ink deep (saturation), can reduce the amount of ink, is conducive to offset printing ink balance control;

- Consider the nature of the substrate, such as whiteness, absorbency, smoothness, etc. If the nature of the paper is far from the paper nature of the original, analyze it according to the specific situation. If it is also telecommunication blue, but Sub-users require the use of pink fragrant cards to print telecommunications logos. If telecommunications blue inks are used, the printed color effects will be dark and gray. The overall hue is far from the original, and we can print directly using sky blue ink. Matching with paper "The effect of rendering color is similar to Telecommunications Blue.

- Consider the influence of the environment surrounding the color sample to avoid illusion of color. When color is identified, the surrounding color should be covered off. Single observation will not cause color shift.

——When the ink layer is obtained by the topography method and the scraping method, the thickness of the ink layer of the spot ink must be similar to the thickness of the original ink layer.

Spot color ink printability requirements are accurate and accurate

The printing properties of general spot color inks are mainly formulated by considering the viscosity, fluidity, and dryness of formulated inks. However, with the development of the ink industry, the suitability of various inks is good and compatibility is good. Generally, we do not need or Only need to add appropriate amount of ink additives, such as special ink additives or varnish, to change the compatibility of formulated ink, you can achieve better printing results.

Matters needing attention: Ink mixing should be mixed evenly; Paper properties such as coated paper, ie coated paper, are generally prepared with quick-drying ink, and offset paper can be formulated with resin ink.

Adjust the number of spot color inks accurately

The amount of ink dispensed is accurate, mainly considering the following factors: the number of prints; the emphasis on the paper's ink absorption; the area of ​​the printed graphics; the strength of the spot color ink; the thickness of the spot ink (density).

If the ink is over-provisioned, the remaining ink will be wasted. If too little is not enough, it will need to be deployed again. If complex colors are encountered, it is difficult to completely match the ink used in the second and the first time. This has a great impact on product quality. influences. Therefore, the actual amount of printing should be slightly more than the actual printing amount, which is also to prevent the stock in the ink fountain from falling below a certain value and causing changes in the ink color.

Dark ink and light ink

The deployment of ink can generally be divided into dark ink deployment and light ink deployment.

Dark ink deployment

Only with the original color ink deployment, do not add any diluting agent, collectively referred to as dark ink deployment, deployment according to the results of the color sample analysis, the determination of the main and auxiliary color, and then according to the design ratio, with the auxiliary color ink by the amount of the main Color ink can be evenly. According to subtractive color theory, the type of primary color ink should be used as little as possible when mixing ink, otherwise it will reduce the brightness of the ink and affect the vividness of the color.

Light ink deployment

The inks formulated with the diluting agents are collectively called the pale inks. Because light-colored inks have less stimulus to human eyes, it is generally necessary to use a magnifying glass to analyze the original color samples, eliminate the diluting agent, and determine the main color. Attention should be paid to the color shift of the ink, which is generally adopted by gradually adding a primary color ink to the diluting agent.

Light-colored ink is generally made up of diluting agent or white ink plus original ink. It is necessary to pay attention to the deployment of light ink based on white ink. Its color powder, ink is fresher, and it has strong hiding power. Because the white ink pigments are easy to be plated, the blankets are piled, and the light resistance is not good, and it is suitable for the monochrome printing of the actual printing field, and is generally a pink-blue pink column spot color ink. Diluted light-based light-colored ink has a certain degree of transparency, does not have hiding power, color is not fresh, suitable for multi-color overlapping printing, usually light red, light yellow, light gray and other series of spot color ink.

To sum up, the deployment of spot color inks, because it involves light color theory, ink, paper, process, etc., make spot color ink deployment more difficult, and is currently based on experience, so the requirements of the transfer of ink personnel Higher, first to master the theory of light color, followed by the need to master the properties of commonly used ink, etc., have a keen, accurate ability to discriminate color, and continue to consciously practice their own application ability through practice, that is to see a certain In hue, you can quickly report the ink ratio. Only in this way can we quickly and accurately match spot color inks to provide better quality services and improve product quality.

Reprinted from: Ink Information