In color printing, the colors should generally conform to the basic requirements of the original manuscript. Except for special cases such as reproductions of ancient paintings, other specially required art and craft products, securities, etc., most color prints have a requirement for bright and vivid colors. How can this quality standard be achieved through color printing techniques and material selection? The author believes that the following conditions must be met in order to achieve vibrant printed colors.
1. Paper Whiteness and Absorption
The whiteness of paper is the foundation for achieving vividly colored prints. Pure white paper reflects almost all color light, whereas gray or black paper absorbs some color light, which affects the hue, brightness, and purity of the print. From the perspective of color analysis, on paper printed with images, aside from the color formed by the spatial mixing of various color dots through additive methods, the surface color of the paper where no dots (or patterns) are printed also participates in this spatial mixing. Gray paper is akin to adding a small amount of ink to each color ink, thus visually it is difficult to see pure colors, instead showing darker and duller shades. Practical experience shows that under identical conditions, the vibrancy of prints on paper with different levels of whiteness varies significantly. Just analyzing from the contrast of color brightness, when only black text is printed, flawless white paper creates a stark contrast with black text, making the black appear darker and the white brighter, forming a distinct contrast. Thus, we can infer: as the basis for printing, the whiteness of paper has a direct relationship with the vibrancy of the print's colors. Similarly, red-tinted paper makes prints lean towards red, while blue-tinted paper makes prints lean towards blue, these are factors to consider during coloring. Additionally, the absorption capacity of paper greatly influences color. Highly absorbent paper allows pigments and binders to seep into the paper, preventing the formation of a sufficiently full ink layer on the paper surface, reducing color saturation, making it difficult to achieve vivid colors.
2. Ink Mixing and Ensuring Color Vividness During Roll Pressing and Coating
From the purity element of the three elements of color, the saturation of a color refers to its purity. To make colors vivid, attention must be paid to selecting the right ink. Besides the relatively pure hues of standard three primary color inks, many original inks are secondary colors of the three primaries, their hues matching the original manuscript to enhance the vividness of the print. To ensure the ink mixed has vibrant colors, particular attention must be given to avoiding complementary colors. For example, when printing lush spring trees, using light yellow ink results in tender green leaves; if deep yellow ink is used, it contains red, which is the complementary color of green, resulting in dark and murky leaves that fail to reflect the freshness of early spring, let alone being vivid. Attention must be paid to the cleanliness of the ink trough and ink rollers during printing. This means preventing contamination from previous inks when changing inks, especially when switching from dark to light colors, or from black and blue to yellow. If cleaning is neglected, discoloration may occur, affecting the vividness of the print's colors.
3. Complete Reproduction of Halftone Dots
When halftone dots expand, the thickness of the ink layer of the expanded color must be reduced, making the low tone and solid parts less substantial, weakening color saturation, failing to fully express the inherent characteristics of the color. Printed clothing appears old, and landscapes look like rainy days.
4. Coloring Power of Ink and the Impact of Emulsification and Dilution
Except for special cases where color dilution is needed, low coloring power of ink, improper addition of auxiliary materials during the printing process that dilutes the ink color, or the addition of auxiliary materials that inhibit drying causing high emulsification of ink, these factors may reduce the saturation of the printed ink. Slow drying after printing, strong penetration, long penetration time, result in an unthick ink layer, leading to not very vivid print colors.
5. Ink Layer Thickness of the Print
Whether the ink layer thickness of the print is appropriately full is a key factor in whether the color conforms to the original sample and whether it is vivid. This is especially important when issuing the proof. The amount of ink layers of each color, if deviating from the original sample, will inevitably cause the final image to lose its true color. Controlling the first color ink quantity is very important. If this foundation is poorly laid, subsequent colors are hard to remedy. In order to make the color close to the original, if the first color ink quantity is insufficient, then subsequent colors must also be reduced, resulting in all color ink layers being insufficient, making it impossible to talk about vivid colors. Conversely, if the first color ink layer is too thick, subsequent colors must also be thicker; otherwise, the color balance will be lost. Although the print's color may resemble the original, due to excessively thick ink layers, low tones become muddy and high tones become flat, resulting in a dull and concentrated picture with unclear layers, making it impossible to achieve vivid color effects. Generally speaking, to achieve a vivid color effect in pictures, the ink quantity must be sufficient. Only then can the ink layers of other color plates be printed fully. Otherwise, over-deep or over-light ink colors cannot be remedied, especially after they have become too deep, making it even harder to remedy. For example, if yellow ink is excessive, it will inevitably cause the color ratio to lose balance, requiring corresponding increases in magenta and cyan ink quantities, although the color is close, but the dots are blurred, leading to a decline in print quality.