Common knowledge about printing

- May 06, 2020-

1. What is the meaning of quality? What is the meaning of print quality?

Quality, also known as quality, reflects the sum of the features or characteristics of a product or service that meet the ability to meet an explicit or implicit need.

Print quality refers to the quality of printing technology in the process of copying printed matter, including absolute quality and average quality.


2. What are the main requirements for the quality of color prints?

The overprint is accurate, the ink color is uniform and bright, the layer is rich, the dots are smooth and full, the field is plain, the text is clear, there is no broken pen, no obvious streaks, no greasy rancidity, no paper hair, no ink skin, etc. Restored to the authenticity of the original.


3. What is the difference between offset printing and other printing?

①Using the basic principle of incompatibility of oil and water to complete printing:

② The blank part and the graphic part are basically on the same printing plate surface, and selectively absorb water and ink;

③The imprint is transferred through the intermediate (rubber roller):

④The tone is presented by the dot size.


4. What is the process principle of offset printing?

Offset printing uses the basic principle that water and oil are incompatible to achieve the printing effect. When printing, add water first, so that the blank part of the layout absorbs water, while the image part repels water. When inking, the blank part repels ink while the image part absorbs ink.


5. What is the ph value in the wetting fluid?

The ph value represents the content value (concentration) of the acid and alkali contained in the wetting liquid, and the negative logarithmic value of the hydrogen ion concentration indicates the acidity and alkalinity of the solution. ph = 7 is neutral solution, ph> 7 is alkaline solution, ph <7 is acid solution.


6. In what range should the pH value of the wetting fluid be controlled?

For the pH value of the ps version of the wetting fluid, it is generally appropriate to control it between 5 and 6.


7. Improper control of the pH value in the wetting fluid, how does it affect the product quality?

Strong acidity: It is easy to cause the printing plate pattern and dot to become smaller, reduce the printing plate durability, the ink is easy to emulsify, resulting in quality defects such as not easy to dry the print, sticky back of the product and so on.

Weak acidity: the printing plate dots are easy to paste, merge, and get dirty, causing paste plates and dirty.


8. What are the characteristics of alcohol wetting?

①Good wetting performance, good spreading performance on the layout;

②Because alcohol has a certain volatility, after the water on the layout is transferred to the blanket, the water has a certain degree of volatility, so the paper's water absorption will be reduced;

③ When the alcohol volatilizes, it can take away a lot of heat, so that the temperature of the plate surface is reduced, and the flow performance of the ink is guaranteed.


9. What is the role of wetting fluid in production?

① Make the blank part not dirty and greasy (not fat-sensitive);

②The hydrophilic property of the blank part is maintained by hydrophilic colloid and organic acid;

③By using surface active substances and surfactants, the blank part of the layout needs less water, so that the blank part can be protected, which is beneficial to the balance of water and ink;

④The pH value of the wetting solution is stabilized by the buffer solution (same ion effect).


10. When printing, what is the effect of the moisture content of the layout and the product quality?

In the printing operation, the water content of the printing plate is difficult to control; when the water content is too large, the product ink color is too light, the ink color is matt, and the color color is not bright. It is not allowed to wait for quality defects; while the moisture is too small, it is easy to make the layout dirty or greasy and the dots appear to be connected and pasted and other quality defects.