Question 1

Why does printing use CMYK? What is CMYK?

Accepted Answer

When sunlight strikes an object, the object absorbs part of the light and reflects the rest; the reflected light is the colour of the object we see. This is called subtractive colour mixing, and it is completely different from the additive colour mixing of RGB. Paper printing applies exactly this subtractive method, which is CMYK.

CMYK is also known as the four process colours: C (Cyan), M (Magenta), Y (Yellow) and K (Black). These are colours formed by pigments, generally used in printing or large-format output. CMYK's colour scale runs from 0 to 100, and overlaying colours makes them darker and darker, which is why it is called the subtractive method — the same principle as mixing watercolours. This mixing relationship is the exact opposite of the RGB colour mode. From the CMYK colour relationship diagram above, we can see that M+Y makes red, C+Y makes green and C+M makes blue, complementary to the RGB colours.

Question 2

Why is the printed product a different colour from what my computer displays?

Accepted Answer

An ordinary computer monitor that has not been colour-calibrated cannot be used directly to confirm printing colours. Because a monitor forms images with RGB light while printed products reflect CMYK light, the imaging principles are entirely different, so there will be a serious colour difference between the monitor and the printed product. In addition, computer monitors display colours differently depending on brand, model and colour settings. We remind everyone again: please do not use monitor colours as a colour-proofing standard.

Besides the force majeure of computer monitors, uncontrollable printing factors such as printing time, environment, press brand and model, ink density, temperature, imposition position and paper properties can also cause slight colour differences. The main cause of such colour differences is mostly a problem with the file settings; please refer to <File Upload Guidelines>

Question 3

Why does gang-run printing have colour differences?

Accepted Answer

Gang-run printing merges multiple different files onto the same plate for printing, so it cannot cater to the colour requirements of each file or adjust them individually. When files are ganged together in a heavy-ink area, the printing colour is affected by the colours of the neighbouring files. If the imposition position leans red, the finished colour will deviate by plus or minus 10%, and so on. A colour difference of plus or minus 10% is an unavoidable and normal phenomenon in gang-run printing, and we cannot accept returns for colour differences within 10%.

In addition, reprinting the same file will also show different colour differences due to different imposition positions. If you want to use economical gang-run printing, when printing cards, gang together as many cards as possible with different names but the same quantity, so as to reduce the situation of one group having many colours.

Question 4

Why can I never print good dark colours?

Accepted Answer

Dark colours are mostly formed by overlaying multiple colours; if a single colour value exceeds 70% — such as dark brown, coffee, dark green, dark blue, purple-blue, etc. — colours made by overlaying multiple high values are hard to balance on the press, so they are all difficult colours to print. To print good dark colours, keep the total four-colour value within 200%; this not only makes them easier to print, but also avoids set-off or ghosting caused by ink that does not dry easily.

Question 5

What black are you using? When do you need K100?

Accepted Answer

We are often asked why the printed colour is not black enough. Apart from the properties of the paper, the main reason is the sequence in which the print colours are overlaid. The press prints starting from the black plate (K), then overlays cyan (C), magenta (M) and yellow (Y). So when K is overprinted with different colour values, it changes according to the density of the different colour values.

Because the paper may shift or wrinkle while running through the press, single-colour printing can suffer misregistration — that is, each single sheet cannot be printed precisely onto the same colour. Blurred colour edges will appear around such misregistered colour blocks. This is very undesirable in graphic-design printing, so we recommend using single black K100 for small text or patterns in your design to avoid the shadowing caused by misregistration.

Question 6

Why distinguish between the print size and the bleed size?

Accepted Answer

Because the machine may not cut accurately during printing, which affects the quality and appearance of the finished product, an extra bleed size must be set during design. The bleed size is usually 1-2mm added to each of the four sides; small items such as cards and postcards can use a 1mm bleed, but large printed products such as posters and flyers need it increased to 2mm. If you do not understand how to set the bleed, you can download various templates from our Download Centre.

Question 7

Why do my text and layout get distorted when someone else opens my AI file?

Accepted Answer

If the text is not converted to curves or outlines before the file is output for printing, and the other person does not have your fonts, their text and layout will become distorted. So all text must be converted to curves or outlines before outputting the print file. We recommend avoiding operating-system fonts as far as possible, such as MingLiU, PMingLiU and DFKai-SB; once these fonts are converted to curves or outlines, the strokes tend to overlap and leave gaps, and the text of the printed product may develop white spots.

Question 8

Is small text unsuitable for multiple colours?

Accepted Answer

In gang-run printing, using multiple colour values for small text can very easily cause ghosting in the text of the printed product. Because offset printing uses the principle of layered printing, laying one layer on top of another, and the paper is stretched during printing and changes, this causes misregistration and ghosting — especially noticeable with synthetic paper or recycled paper.

Question 9

Why can gang-run printing not be proofed?

Accepted Answer

Gang-run printing exists to share the cost of the plate, printing and paper by combining all files together for imposition and printing, so the price is low and small print runs are acceptable. Because the imposition position and the colour values of the ganged files differ every time, you cannot use a previous printed product or a proof to check the colour. In addition, the colour of gang-run printing varies slightly each time due to uncontrollable factors such as printing time, ink density, temperature and paper properties.
Besides colour mismatches, proofs generally use digital printing, whose finished colours are more vivid, which makes them even harder to compare with gang-run printed products. In view of this, there is no proofing service for gang-run printing.

Question 10

Why are the images in my printed product very dark?

Accepted Answer

Many people printing for the first time have experienced their printed images coming out darker than the text and other design elements. 90% of the time this is because the images were not converted from RGB to CMYK when preparing the file, and the image brightness was not adjusted. This is a mistake many beginners make, because most images are in RGB colour. If they are not converted to CMYK, the press will convert the images to CMYK on output directly, and this conversion makes the images darker.

Question 11

White edges appearing on folded paper?

Accepted Answer

Whether folded paper cracks along the edge depends on the paper quality, such as the grain direction, thickness and printed colour. Thick paper is not suitable for direct folding; folding it directly will cause the paper to crack. This is especially the case when the base colour of the printed product is dark, creating a stark contrast between the white cracks and the base colour. Thinner paper can be folded more times than thicker paper — in other words, the thicker the paper, the more easily it cracks and shows white edges. How to avoid cracking: · Use thinner paper: the fibres of thick paper are denser and crack more easily. · Score before folding: press a groove into the surface of the paper before folding, which reduces cracking. · Laminate before folding: lamination provides protection, and scoring and folding afterwards greatly reduces cracking.

Question 12

Why are there bubbles after lamination?

Accepted Answer

The surface of laminated paper will have film marks, which are more easily noticed when printing full, dark colour blocks. This is not caused by uneven printing ink or bubbles between the film and the paper; it is unavoidable. It is especially obvious with matte lamination, because matte film does not reflect light, so the film marks are even more obvious over a dark base.

Question 13

Why does the text stick together after hot foil stamping?

Accepted Answer

Hot foil stamping uses heat to press the foil onto the paper product; glossy coated paper is usually chosen because its surface is porous, allowing the hot air between the foil and the paper to escape. If stamping onto paper without pores, the foil will bleed because the hot air cannot escape, affecting the finished product. In addition, when the text or pattern to be stamped is too small, the lines too thin, or two foil areas too close together, the foil may stick together, so you must prepare artwork according to <Artwork Guidelines>. Foil is mostly glossy, though some people use a matte finish.

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Common Printing Questions

Common Colour Problems

Common Pre-Press Questions

Common Post-Press Questions