Fundamentals of Printing - Putting a print in print (fixing white spots)

 

In the production process of printing packaging, fine art books, and various paper publications, color reduction and edge accuracy are the key factors determining the quality of the finished product. However, because the paper will undergo physical morphological changes (such as hygroscopic expansion, dry contraction) during the printing process, the ink cover of different colors is different, and the conformity accuracy of the printing equipment is limited, and the boundaries of adjacent colors are very prone to problems such as loose whiteness, edge jagging or pattern mislocation. In order to compensate for these unavoidable errors and ensure the visual coherence and integrity of the picture, a crucial technology in pre-press design - trapping - came into being.​​​​

​​I. What is a camouflage (whitespace)?

​​The core principle of indentation, also known as leakage or expansion, can be summarized as "light color to dark color, cold color to warm color, monochrome to multichrome, solid bottom to line."

 

When two adjacent color blocks are pressed against each other, in order to avoid revealing the underlying color of the paper at the junction after printing due to paper deformation or improper printing (commonly known as "whitening"), Before printing, the designer will proactively extend the edge of the light or weak color side by a tiny width, and the edge of a dark or strong color side will contract inward, thereby eliminating the gap visually.

II. Basic guidelines and thinking for trapping problems

In order to ensure that the trapping effect is aesthetic and does not affect the quality of the picture, the industry has formulated a strict set of treatment guidelines:

1. The principle of "three expansions, three non-expansions"

​Light color does not extend to the upper color, light color doesn't extend to the dark color: this is to avoid damaging the purity of the dark color area. For example, a light yellow block intersects with a dark blue block, and the light color should extend to the dark color.

​Lower color does not expand color, expand the flat network does not extend the field: the flat network points are easy to paste, and the ink layer on the field is thick, which needs to be adjusted according to the actual situation.

​The boundary between four colors and specialized colors should not be widened: avoid affecting color reduction.

2. The margin of the indentation is thin

​Software default value: usually between 0.1-0.2mm.

​Fine lines, small text (< 0.2mm): It is recommended to use ≤ 0.1mm small trapping or direct overprint, large area color blocks can be appropriately increased.

​Thick line, large text (> 0.2mm): generally controlled in 0.08-0.15mm.

3. Special Color and Graphic Processing

​​​Color priorities: Black, gold, silver and specialty colors are "non-expanding colors" and other colors move closer to them. Small areas of special colours are suggested to print directly on top to reduce indentations.

Illustration and text separation: No margin stamps are made at the border between the pure four colors and the four colors, and a superprint is directly placed;Proximity colors with high dimensions (which share ≥ 20% of the primary color component) can simplify or omit imperfections.

​Gradient and image: continuous tone image does not actively expand, adjacent colors (such as meat / peach) slightly expand (≤ 0.15mm), and can be added at the junction of a very narrow mixed ribbon weakening transition.When the gradient color block is the same as the real color, the real color side gradually expands, and the gradient side does not expand, so as to prevent the gradient layer from breaking.

III. Common printing scenarios and practical methods

In practice, designers often face complex interactions between four colors, monochrome, and color. Here are a few typical printing scenarios:

1. Four Colors and the Four Color Imprinting

​Contain common colors: If two colors contain each other's colors (e.g. purple = blue + red), you don't need to be offset and use the color preview panel to see it.

No common color:​

​High contrast combination: Light color expands to dark color to avoid excessive indentation causing the edges to sag, and thin lines need to reduce the indentation value appropriately.​Middle contrast combination: Green is expanded to strong colors, priority is given to visual effects, and after drawing a sample, confirm whether the edges are natural.​Low contrast combinations: Only a small amount of expansion or non-expansion is allowed, and equipment with high precision (such as Heidelberg) can be omitted to avoid margin blurring.

2. Four Colors and Monochrome Printing

​Four colors overlap with monochromes: It is often followed by a "light color to dark color, yellow to dark color." Because dark colors (especially glossy colors) have more coverage power, lighter colors expanding to dark colors will not obscure dark colors, while reverse colors will cause dark colors to be covered.

​Specialty color and specialty color: judge whether or not to make a false print based on the brightness, color difference and actual printing process. If the contrast is strong (e.g. bright yellow versus dark red) or the color is close, it is advisable to apply a small amount of imprint or not to do it at all.

3. Monochrome and Color Fading

​The background is monochrome black, the text is text/色Block Color: Extend the color portion outward to avoid whiteness.

​Base color, text monochrome: Monochrome adds monochrome offset to the color background and edges, and manually offsets.

4. Four Colors and White Camouflage

​Text and white borders: Text is filled with single black / double print, and do offset processing.

Colored characters on white background: The background color expands to white text (outsize).

​White characters on a color background: text with single-black offset edges and offset treatment.

IV. A pit shelter guide: design considerations before printing

Even if you have mastered the printing rules, you still need to pay attention to the following details in actual operation, otherwise it is easily counterproductive:

​​​Document format and font: PDF / X-1a or PDF / X-4 format are preferred; All text must be distorted to avoid the lack of the corresponding font on the printer's computer causing the text to be distorted or lost.

​Resolution and color mode: the resolution is usually 300ppi; Printing must use CMYK mode, prohibit the direct screen display RGB mode file output, RGB to CMYK need to be completed in professional design software.

​Monochrome black treatment: Monochrome black in prepress treatment special K = 100%, C = M = Y = 0% black, often used in text, thin lines and other elements, to ensure that printing and brushing edge polychromatic overprinting accurate.

​Bleeding point setting: Bleeding refers to the edge (usually 3mm) reserved in printing to preserve the valid content of the picture, in order to avoid a white edge caused by a shift during tailoring.

V. CONCLUSIONS

Imprinting is an 'invisible art'. Excellent framing allows the reader to completely ignore the color splice and feel a smooth visual experience when leafing through the print. A failed imprint can lead to blurred edges, fragmented patterns and even color distortion. For pre-production designers, therefore, understanding printing principles, following printing guidelines, and making flexible adjustments in line with actual processes are key to ensuring the delivery of printed products with zero defects.

 www.eufuho.com