Printing color sequence refers to the order in which each color plate is overprinted in a single color unit in multi-color printing. For example, a four color printing machine or a two color printing machine is affected by color sequence. Simply put, different color order arrangements are used in printing, resulting in different printing effects. Sometimes, the color order determines the aesthetics of a printed product.

One： Reasons for arranging the printing color sequence

① The impact of ink overprinting and the drawbacks of ink pigments themselves

② Quality of paper

③ The ability of the human eye to recognize colors

The most fundamental reason is the incomplete transparency of the printing ink itself, that is, the covering power of the ink itself. The subsequent printing ink has a certain covering effect on the first printing ink layer, resulting in the color presented in the printed product always emphasizing the representation of the latter color, or in other words, the mixture of the latter color and the front color.

Two： Factors affecting printing color order

1. Considering the transparency of ink

The transparency of ink is related to the hiding power of the pigments in the ink. The so-called ink coverage refers to the covering ability of the covering layer ink to cover the underlying ink. Poor covering power results in strong ink transparency, while strong covering power results in poor ink transparency. Generally speaking, ink with poor coverage or strong transparency should be placed on the back for printing, so as not to obscure the brilliance of the front printing ink for color reproduction. The relationship between ink transparency: Y>M>C>K.

2. Considering the brightness of the ink

Low brightness prints first, high brightness prints later, that is, deep ink prints first, and light ink prints later. Because the higher the brightness, the higher the reflectivity, and the brighter the reflected colors. Moreover, if light colors are overprinted on dark colors, minor overprinting errors may not be very noticeable; If dark colors are applied over light colors, they will be exposed completely. Overall, the relationship between the brightness of ink is Y>C>M>K.

3. Considering the drying speed of ink

Those with slow drying speed print first, and those with fast drying speed print later. If printing quickly first, for a monochrome machine, it is easy to glass and not conducive to fixation due to wet pressing and drying; For multi-color machines, not only is it not conducive to the overprinting of the ink layer, but it can also easily cause other problems, such as dirty back rubbing. The order of ink drying speed: yellow is twice faster than red, red is twice faster than green, and black is the slowest.

4. Considering the properties of paper

① Surface strength of paper

The surface strength of paper refers to the bonding force between fibers, fibers, adhesives, and fillers on the surface of the paper. The greater the bonding force, the higher the surface strength. In printing, the degree of paper peeling and shedding is commonly used to measure. For paper with good surface strength, that is, high adhesion, and difficulty in peeling and shedding, we should first print ink with high viscosity. Printing with the first color of high viscosity is also beneficial for overprinting;

② For paper with good whiteness, dark colors should be printed first and then light colors;

③ For rough and loose paper, light colors are printed first and then dark colors.

Three： Principles that must be followed for printing color sequence

The color sequence of printing directly affects the quality of printed products. In order to achieve good replication results, the following principles must be followed:

1. Arrange the color order according to the flat screen and on-site arrangement

When there are flat screens and on-site copies, in order to achieve good printing quality and ensure that the on-site printing is smooth and the ink color is bright and thick, the flat screen graphics and text are generally printed first, and then the on-site structure is printed.

2. Arrange color order based on light and dark colors

To add light colors to the printed material in order to give it a certain gloss, dark colors are printed first, followed by light colors.

3. Arrange the color order based on the area of the image and text

The image and text area of the green version of landscape products is much larger than that of the magenta version. Based on the principle of printing after the color version with a larger image and text area, it is advisable to use black, magenta, green, and yellow sequences.

4. Products mainly based on text and black fields

Products that mainly use text and black fields generally use cyan, magenta, yellow, and black sequences, but black text and patterns cannot be printed on yellow fields. Otherwise, due to the low viscosity of yellow ink and the high viscosity of black, reverse overprinting will occur, resulting in the phenomenon of black printing not being able to be printed or not being solid.

5. Products with small areas of four color overprinting

For images with small areas of four color overprinting, the color sequence can generally follow the principle of printing after the color plate with a large image and text area.

6. Gold and silver products

Gold and silver products, due to the low adhesion of gold and silver inks, should be placed on the last color as much as possible. Generally, it is not advisable to use triple ink printing.

7. Four color machine printing and five color printing

The color sequence of printing should be as consistent as possible with the color sequence of the sample, otherwise it will not keep up with the effect of the sample.

If it is a 4-color machine that prints 5 colors, it is necessary to consider the issue of embossing or overprinting. Generally, the color overprinting at the bite position is more accurate. If there is also overprinting, it is necessary to do trapping, otherwise the overprinting may not be accurate and may leak white.