How to Improve Printing Quality from Details?

- Sep 20, 2019-

When we choose a commodity, the first thing we see is the packaging. Whether the packaging is beautiful will directly affect people's buying behavior.As packaging is generally printed in large quantities, it is inevitable that unsatisfactory parts will appear in the printing process.How can we improve the quality of printed matter as much as possible?Whether it is digital printing or traditional printing, the handling of fine elements is of vital importance.Let's talk about some experiences from the processing of printed words and lines.

Use vectorized text and lines whenever possible

For books, newspapers, periodicals and picture books, as designers used typesetting software such as Founder Book Edition or InDesign at the beginning of design, the final document is naturally a vector document.However, for packaging, many designers will use Adobe Illustrator, CorelDRAW, Photoshop (hereinafter referred to as "AI, CDr, PS") software according to their personal habits. If PS is selected to be converted into Tiff format as the final file, since the file belongs to bitmap file and does not have vector attribute, its printing quality will not be ideal. How do vector file and bitmap file affect the printing quality?

In fig. 1, A shows the effect of 50% gray bitmap screening. We can see that due to the inaccuracy of pixels, after screening, there will be miscellaneous points on the edge of the color block, which is what we call burr or jagged edge phenomenon. B is the effect of 50% gray vector diagram after screening, obviously, even if the dot is only half, the whole edge is neat.This is the difference in screening calculation results caused by different file attributes.For small elements, the printing quality of vector files is much higher than bitmap files.If you look closely, although digital printing does not have such obvious dots as those in fig. 1, the difference between bitmap and vector printing is also reflected.

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  AI and CDr are the most commonly used vector diagram making software. Using these two softwares to design packaging files will not cause the problems faced by diagram A in Figure 1, which is why many printing houses strongly recommend designers to use these two softwares to design packaging.

If the packaging is designed with PS and there are a large number of small words and lines, the final output can be EPS files, and vector attributes can also be retained.However, the disadvantage is that the amount of file data is very large, which will slow down the running speed of the computer during subsequent operations.

Choice of Color Matching

For the color allocation of small elements in packaging design, designers have an unwritten rule, that is, the maximum three-color theory, in other words, the less the number of colors, the better.When printing machines overprint in multi-colors, large areas of elements are still not obvious. For small words and lines, even the most advanced machines will produce overprint deviation due to improper operation and machine errors when overprinting in multi-colors. This is what we call double printing.There are many small words on the package. All kinds of descriptive words, trademarks, bar codes, etc. need to consider the overprint problem caused by the color configuration.

Some friends may ask whether it is good to use three colors or less when configuring colors for an element.This problem needs to be solved by the designer himself. Simple colors can also match beautiful pictures.Designers' creativity is endless. Although printing is a four-color mode, the colors that can be mixed with three or two colors are still very rich.

In order to avoid overprint errors as much as possible, many packages have considered the use of spot color at the beginning of planning. Spot color is the best scheme to avoid overprint. It can not only print out colors that cannot be realized by four colors, but also avoid the appearance of dot and, more importantly, overprint.This is why spot colors are widely used in toothpaste boxes, medicine boxes, flexible packages, etc.

How to Handle Black Characters and Lines

Here's the point.Black text and lines are explanatory and informative elements on the package, and the printing quality must be clear and complete.How to deal with such elements?

1. Black text on white background

This kind of situation is the most simple, set to single black 100(K100), black and white, soap and white clear.However, many new designers use four-color black in this case. The printed text looks particularly heavy, bloated, and the hue is not pure black. At the same time, it also causes some unnecessary troubles to the printing master.

2. Black Text with Color Background

This kind of situation is the most common. How should we deal with the company name or instructions printed on the color screen?Is it ok to set it to K100?Of course not!

In fig. 2, a is four-color overprint black on a color background, b is hollow overprint monochrome black, and c is overprint monochrome black.A overprint is not allowed to double, b overprint is not allowed to show white, only c is the most suitable.C does not require strict overprint, even if there is a slight printing error will not affect the appearance and clarity.A should be avoided as much as possible, while for b, some designers will say, why do I need overprint when I have already set it to black?This is still not a correct understanding of the concept of overprint.C is the real single black overprint.How to realize single black overprint?

The implementation of single black overprint will vary slightly depending on the software used.If the packaging is designed by PS, after the text is set to K100, the effect shown in C can be achieved by changing the layer mixing mode of the text layer to "positive overlapping bottom".If AI or ID and other software are used, it needs to be previewed by overprint check. Some software will automatically recognize that K100 elements are automatically set to overprint mode. If there is no automatic setting, it also needs to be manually set to "positive stack bottom".Otherwise, the situation shown in b will appear.

It is worth noting that black overprint on color background is only suitable for K100 elements. If it is dark gray or lighter gray, black overprint cannot be used. After overprint, it will merge with color background into darker color and cannot achieve the expected effect. Hollow overprint must be considered at this time.

This will also lead to another question. Will K100 elements overprinted on a colored background not show pure black?This depends on the situation. If it is a large area of black elements, such as characters and patterns with a large font size, K100 overprinted on the color background will be biased towards the color of the background color. If the background is a color pattern, there will even be some dark lines inside the overprinted black characters.In this case, black hollow overprint should be used. Some designers will add 70% cyan to K100 in order to make the printing effect of large-area black characters or patterns darker.If it is a small text or line, it is not necessary to consider the above-mentioned problems, and it can be directly set to K100 overprint, because small area black will not be recognized by human eyes even if there is slight color deviation, and the overprint accuracy is the most easily detected by human eyes.I remember when I first entered the business, I asked a printing master whether black would change color when imprinted on a colored background. He said that no color could cover black, and I still have a deep memory.

3. Black text with white edges

This kind of situation is also very much, in order to make the text better distinguish from the background, designers will add white border effect to the text, this kind of situation can't use "positive film overlay".

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In fig. 3, both a and b are K100 text added with the effect of tracing edges. a sets the effect of "positive overlapping bottom", while b does not.The single black text in Figure A needs to be overprinted with the text with the same background color inside the white edge on the background color. The single black text in Figure B only needs to fall into the white area on the background color, and even slight deviation will not affect the beauty and clarity.

This kind of situation seems simple, in fact, it requires designers to be very familiar with the software performance and printing principles to understand, so an excellent designer not only needs high design ability, but also needs to have a thorough understanding of the subsequent printing process.

4. Black text with color strokes

This is also a type, which is different from the third type and has nothing to do with the background color, because the color stroke has become the background color of black text.

In fig. 4, all the black characters have red strokes.Fig. a shows the effect of setting "positive overlay" after stroke of K100 characters. black characters need to be overprinted with colored characters on the background.Figure B shows that K100 characters are not set with "positive overlapping bottom". Black characters need to be overprinted with white hollowed-out characters on the background.Only K100 characters in the C chart do not need accurate overprint, only need to be pressed onto red characters, even if there is slight deviation.So how to realize the effect of C diagram?The method is very simple, taking the text shown in the figure as an example, the stroke color is M100Y100, and the black text can be filled with M100Y100K100 without any other operations.In other words, when matching colors for black text, K100 is added to the stroke color.

Through this example, we can see that in any case, for small black characters and lines, avoiding accurate overprinting is the king to ensure printing quality, and even with high-quality printing equipment as the backing, this problem needs to be considered.This kind of situation cannot be foreseen by designers in the office, and even if digital proofing is used, the risks involved in overprint accuracy cannot be found.This requires designers to go to the printing workshop to have a look, to communicate with the printing masters and to understand the printing principles, so as to ensure that the design scheme can be perfectly reproduced in printing.

Compared with other printed materials, packaging pays more attention to printing accuracy and quality. Of course, this is not to say that other printed materials do not pursue the quality of printed materials, but to say that besides protecting products, the more important function of packaging is to attract consumers and accurately transmit the information of commodities, especially the text elements with explanatory function. Printing accuracy must be ensured.Only in this way can consumers have a sense of trust in products and then turn into purchasing desire.Rough packaging and printing are difficult to stimulate purchasing desire.

Only by paying attention to every detail and striving for perfection can the printing factory design outstanding works that can be put into production and not only exist in computers.