Spot color printing is a relatively four-color printing process. The four-color printing process generally refers to the printing process of using Y, M, C, and BK four-color inks to reproduce the color originals, while the spot color printing refers to using other color inks other than the Y, M, C, and BK four-color inks. Copy the original's printing process. Spot color inks can be supplied by the ink manufacturer, and Y, M, and C inks can also be used for self-provisioning. This article will compare the printing effect of spot color and traditional four-color, what is the case with spot color printing, and the introduction of spot color ink deployment methods. I hope we can discuss it with everyone to further understand spot colors.
1 Comparison of spot colors and traditional four-color printing
From the visual effects of color, the advantage of spot color printing is that spot color inks are formulated using Y, M, and C primary inks according to the principle of subtractive mixing of color materials, and their color brightness is lower and the saturation is higher. Ink solid ink is usually printed in spot color, and the amount of ink is appropriately increased. When the thickness of the ink layer on the layout is large, the sensitivity of the change in the thickness of the ink layer to the color change is reduced, so the ink is uniformly and thickly printed easily. effect. The four-color printing results in the combined effect of additive and subtractive absorption of the dots, and the lightness of the patches is higher and the saturation is lower. The use of four-color printing process overprint color blocks, due to the composition of the color of the various colors are mostly composed of a certain percentage of network points, when printing dot network ink thickness is strictly controlled, easy to change the thickness of the ink layer and the printing process conditions The change causes a change in the color intensity and dot gain, resulting in a change in color. Moreover, any change in the color of the color block will cause the color of the color block to change, so that the chance of occurrence of uneven ink will multiply and prone to color shift. If four-color printed light-colored color blocks are used, the lack of ink-to-paper coverage results in a lack of a solid feel. In addition, the spot color printing is stable in hue, and the printed products are clean and flat, which can also prevent the occurrence of moire failures due to the improper arrangement of the dot positions.
With the usual four-color printing, only a limited gamut space can be reproduced, and spot color printing can reproduce more gamut spaces, so that a more ideal and more natural printing effect can be reproduced. Spot color printing faithfully restores the image and enhances the vivid color and print quality of the copied color.
The following two figures are used as examples to compare the actual printing effects of spot color printing and traditional four-color printing. The five-color printing image in FIG. 1 is printed using three primary color inks C, M, Y, black ink K, and spot color rY ink (Y100M50), and the orange hue reproduced is consistent with the original, highlighting the freshness of the fruit; and FIG. The color printing image uses the usual four-color ink, and the orange color at this time is overprinted by yellow ink and magenta ink, and the reproduced color looks somewhat old.
2 From the perspective of improving product quality, what kind of product is suitable for spot color printing?
In general packaging printing, spot color printing is often used to print a large area of ​​background color. The cover of a packaged product or book is often composed of uniform color blocks of different colors or regular gradient patches and texts. These blocks and texts can be color-coded and overprinted with four-color inks. Spot color inks can also be used for printing. In the comprehensive consideration of reducing the number of overprints and improving the printing quality, spot color printing should be used. For color photographs that reflect the colorful changes in the natural world, the artist's color artwork or other screens containing many colors, for the sake of craftsmanship, must reflect a rich hierarchy and restore the tone of the picture. Should use four-color printing process to complete the copy.
When printing large-area light-colored homogeneous color patches and large-area dark-colored color patches, spot color printing is generally used from the viewpoint of improving product quality.
When printing light-colored blocks, a diluting agent is added to the primary color ink to prepare a spot color ink, and then field printing is performed, so that the ink layer is thick, and it is relatively easy to obtain a uniform color and a thick effect. If printing with a four-color printing process, low-level flat screen dots must be used, but low-number dots tend to be small due to minute sand particles or poor suction during the printing, resulting in uneven ink. In addition, the ink of the small dots may be poorly transferred due to excessive water supply to the printing surface, accumulation of the paper powder on the printing plate and the blanket, and low paper smoothness during the printing, so that the ink becomes lighter and the ink is uneven.
For dark, large-area color patches, the use of four-color printing processes may need to be superimposed by high-number dots of several colors. The ink layer is too thick to cause back-scratching. The use of spot-color printing requires only one color. It is not easy to appear dirty on the back, but also avoid the possibility of overprinting.
If the screen of a product has both color-graded and large-area backgrounds, the color-graded screen portion can be printed in four colors, and the large-area background color can be printed in spot colors. The advantage of this is that the four-color printing part can correctly restore the picture by controlling the solid density, and the under color part can obtain a uniform and thick ink visual effect by appropriately increasing the ink volume.
3 spot color ink preparation method
Spot color inks generally refer to a variety of color inks other than those produced by ink manufacturers. In order to skillfully and accurately deploy spot color inks, it is necessary to master basic knowledge of ink chromatics.
1) Ink base base color inks include primary inks, standard inks, and standard multi-color inks.
Primary color ink: refers to three primary color inks that cannot be mixed by other colors, namely yellow, magenta, and cyan inks. The four-color ink standards produced by different countries and manufacturers are different. For example, the colors of the four-color offset printing inks in our country are designated medium yellow, magenta, sky blue and black.
Standard color ink: refers to the color ink formed by the equal mixing of any two primary color inks. Such as large red, the mixing ratio is yellow 50%, magenta 50%.
Standard multi-color ink: refers to any color ink that is mixed in equal amounts of two different colors or mixed in three different colors. Such as bronze, the mixing ratio is yellow 50%, magenta 25%, cyan 25%.
2) Dark spot color ink deployment
Only with the original color ink deployment, without any diluting agent for spelling color collectively referred to as dark ink deployment. According to the principle of subtractive color, the number of primary color inks should be used as little as possible when deploying dark ink, otherwise the brightness and vividness of the ink will be reduced. However, in the deployment of mixed color inks with different proportions of the three primary colors, the color shift must be corrected by the complementary color theory. If the green phase is too heavy, a small amount of magenta ink may be added to correct it; the red taste may be too heavy, and a small amount of blue ink may be added for correction; if the purple taste is too heavy, a small amount of yellow ink may be added to adjust. Spot blue is commonly used in spot color inks, it can eliminate the original brown bottom in black ink and make black ink darker and thicker.
3) Light-colored spot-colored inks are formulated with ink color tones that need to be added with thinner or white ink. The method of adding a diluting agent to the primary color ink cannot be adopted for the deployment of the light color ink, because the primary color ink has a strong color rendering ability in the diluting agent, and the primary color inks have different coloring powers, which easily causes inaccurate hue and wastes the original ink. The correct deployment method is to gradually add the primary color ink in the diluting agent, so that it is easy to control the change of the color phase, and after the color phase meets the requirement, the ink volume required for the proportion deployment is enlarged.
4) Several points should pay attention to the deployment of spot color ink
1 Take into account the characteristics of post-press processing. There are many surface treatment methods for packaging products, such as laminating, coating, etc. After the surface treatment of the printed products, there will be changes in hue and color density in different degrees, so these conditions should be taken into consideration when selecting inks. For example, if the printed product needs to be glazing, the general ink can be selected. If the ink with good abrasion resistance is selected, not only the cost is high, but also the glazing effect is affected.
2 To see colors under the same light source, a light source with a color temperature of 6500K is generally used as the inspection light source.
3 ink deployment is based on the principle of subtractive color, so as much as possible with a small variety of primary color ink.
4 In addition to the hue of the formulated ink is accurate, the printability of the ink is also important, such as adhesion, viscosity, emulsification, etc., sometimes need to add a certain amount of additives to change the printability of the ink.
5 Match the spot color ink with the printing paper to avoid the color error caused by different paper.
In short, the spot color ink has high requirements for the accuracy of color. Its qualification is not based on the approval of the deployment personnel, but is based on the customer's satisfaction after printing the printing products in the printing factory. To master the deployment technology of spot color inks, it is necessary to accumulate more experience in practice.
Source: "Printing World"
Sino-German Printing Training Center Ai Hairong
1 Comparison of spot colors and traditional four-color printing
From the visual effects of color, the advantage of spot color printing is that spot color inks are formulated using Y, M, and C primary inks according to the principle of subtractive mixing of color materials, and their color brightness is lower and the saturation is higher. Ink solid ink is usually printed in spot color, and the amount of ink is appropriately increased. When the thickness of the ink layer on the layout is large, the sensitivity of the change in the thickness of the ink layer to the color change is reduced, so the ink is uniformly and thickly printed easily. effect. The four-color printing results in the combined effect of additive and subtractive absorption of the dots, and the lightness of the patches is higher and the saturation is lower. The use of four-color printing process overprint color blocks, due to the composition of the color of the various colors are mostly composed of a certain percentage of network points, when printing dot network ink thickness is strictly controlled, easy to change the thickness of the ink layer and the printing process conditions The change causes a change in the color intensity and dot gain, resulting in a change in color. Moreover, any change in the color of the color block will cause the color of the color block to change, so that the chance of occurrence of uneven ink will multiply and prone to color shift. If four-color printed light-colored color blocks are used, the lack of ink-to-paper coverage results in a lack of a solid feel. In addition, the spot color printing is stable in hue, and the printed products are clean and flat, which can also prevent the occurrence of moire failures due to the improper arrangement of the dot positions.
With the usual four-color printing, only a limited gamut space can be reproduced, and spot color printing can reproduce more gamut spaces, so that a more ideal and more natural printing effect can be reproduced. Spot color printing faithfully restores the image and enhances the vivid color and print quality of the copied color.
The following two figures are used as examples to compare the actual printing effects of spot color printing and traditional four-color printing. The five-color printing image in FIG. 1 is printed using three primary color inks C, M, Y, black ink K, and spot color rY ink (Y100M50), and the orange hue reproduced is consistent with the original, highlighting the freshness of the fruit; and FIG. The color printing image uses the usual four-color ink, and the orange color at this time is overprinted by yellow ink and magenta ink, and the reproduced color looks somewhat old.
2 From the perspective of improving product quality, what kind of product is suitable for spot color printing?
In general packaging printing, spot color printing is often used to print a large area of ​​background color. The cover of a packaged product or book is often composed of uniform color blocks of different colors or regular gradient patches and texts. These blocks and texts can be color-coded and overprinted with four-color inks. Spot color inks can also be used for printing. In the comprehensive consideration of reducing the number of overprints and improving the printing quality, spot color printing should be used. For color photographs that reflect the colorful changes in the natural world, the artist's color artwork or other screens containing many colors, for the sake of craftsmanship, must reflect a rich hierarchy and restore the tone of the picture. Should use four-color printing process to complete the copy.
When printing large-area light-colored homogeneous color patches and large-area dark-colored color patches, spot color printing is generally used from the viewpoint of improving product quality.
When printing light-colored blocks, a diluting agent is added to the primary color ink to prepare a spot color ink, and then field printing is performed, so that the ink layer is thick, and it is relatively easy to obtain a uniform color and a thick effect. If printing with a four-color printing process, low-level flat screen dots must be used, but low-number dots tend to be small due to minute sand particles or poor suction during the printing, resulting in uneven ink. In addition, the ink of the small dots may be poorly transferred due to excessive water supply to the printing surface, accumulation of the paper powder on the printing plate and the blanket, and low paper smoothness during the printing, so that the ink becomes lighter and the ink is uneven.
For dark, large-area color patches, the use of four-color printing processes may need to be superimposed by high-number dots of several colors. The ink layer is too thick to cause back-scratching. The use of spot-color printing requires only one color. It is not easy to appear dirty on the back, but also avoid the possibility of overprinting.
If the screen of a product has both color-graded and large-area backgrounds, the color-graded screen portion can be printed in four colors, and the large-area background color can be printed in spot colors. The advantage of this is that the four-color printing part can correctly restore the picture by controlling the solid density, and the under color part can obtain a uniform and thick ink visual effect by appropriately increasing the ink volume.
3 spot color ink preparation method
Spot color inks generally refer to a variety of color inks other than those produced by ink manufacturers. In order to skillfully and accurately deploy spot color inks, it is necessary to master basic knowledge of ink chromatics.
1) Ink base base color inks include primary inks, standard inks, and standard multi-color inks.
Primary color ink: refers to three primary color inks that cannot be mixed by other colors, namely yellow, magenta, and cyan inks. The four-color ink standards produced by different countries and manufacturers are different. For example, the colors of the four-color offset printing inks in our country are designated medium yellow, magenta, sky blue and black.
Standard color ink: refers to the color ink formed by the equal mixing of any two primary color inks. Such as large red, the mixing ratio is yellow 50%, magenta 50%.
Standard multi-color ink: refers to any color ink that is mixed in equal amounts of two different colors or mixed in three different colors. Such as bronze, the mixing ratio is yellow 50%, magenta 25%, cyan 25%.
2) Dark spot color ink deployment
Only with the original color ink deployment, without any diluting agent for spelling color collectively referred to as dark ink deployment. According to the principle of subtractive color, the number of primary color inks should be used as little as possible when deploying dark ink, otherwise the brightness and vividness of the ink will be reduced. However, in the deployment of mixed color inks with different proportions of the three primary colors, the color shift must be corrected by the complementary color theory. If the green phase is too heavy, a small amount of magenta ink may be added to correct it; the red taste may be too heavy, and a small amount of blue ink may be added for correction; if the purple taste is too heavy, a small amount of yellow ink may be added to adjust. Spot blue is commonly used in spot color inks, it can eliminate the original brown bottom in black ink and make black ink darker and thicker.
3) Light-colored spot-colored inks are formulated with ink color tones that need to be added with thinner or white ink. The method of adding a diluting agent to the primary color ink cannot be adopted for the deployment of the light color ink, because the primary color ink has a strong color rendering ability in the diluting agent, and the primary color inks have different coloring powers, which easily causes inaccurate hue and wastes the original ink. The correct deployment method is to gradually add the primary color ink in the diluting agent, so that it is easy to control the change of the color phase, and after the color phase meets the requirement, the ink volume required for the proportion deployment is enlarged.
4) Several points should pay attention to the deployment of spot color ink
1 Take into account the characteristics of post-press processing. There are many surface treatment methods for packaging products, such as laminating, coating, etc. After the surface treatment of the printed products, there will be changes in hue and color density in different degrees, so these conditions should be taken into consideration when selecting inks. For example, if the printed product needs to be glazing, the general ink can be selected. If the ink with good abrasion resistance is selected, not only the cost is high, but also the glazing effect is affected.
2 To see colors under the same light source, a light source with a color temperature of 6500K is generally used as the inspection light source.
3 ink deployment is based on the principle of subtractive color, so as much as possible with a small variety of primary color ink.
4 In addition to the hue of the formulated ink is accurate, the printability of the ink is also important, such as adhesion, viscosity, emulsification, etc., sometimes need to add a certain amount of additives to change the printability of the ink.
5 Match the spot color ink with the printing paper to avoid the color error caused by different paper.
In short, the spot color ink has high requirements for the accuracy of color. Its qualification is not based on the approval of the deployment personnel, but is based on the customer's satisfaction after printing the printing products in the printing factory. To master the deployment technology of spot color inks, it is necessary to accumulate more experience in practice.
Source: "Printing World"
Sino-German Printing Training Center Ai Hairong
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