How to avoid offset printing color difference?

Feb. 14, 2023

Color difference in printing is also called color cast, which is one of the typical disadvantages in the whole process of printing and packaging. In the process of processing, it often happens that the printed matter does not match the color of the proof sheet, or the color of the pattern design interface is overprinted and mixed. Faults can endanger product quality in mild cases, or scrap the entire batch of products in severe cases, just like when we buy things online, merchants will always note in the product pictures that "there may be color deviations, please refer to the actual color." Now let the printing master of RX packaging introduce to you the specific reasons for the color difference in the printing of the packaging box.

Packaging box

1. The dots of yellow, magenta, and cyan caused by substandard printing and plate-making operations are too dark or too shallow.

The main point here is that during the printing process, the intensity of the ink printing light source, the spectrometer does not match the photosensitive characteristics of the printing plate, or the exposure time is not good, the pH value of the developer and the development time are not properly grasped, etc. Both will cause the printing plate dots to be too deep or too shallow.

2. The color preparation of printing ink is not good or the printing ink of three primary colors does not match.

That is not the same brand, the same printing ink. For products printed on the front and back, we must pay attention to the shade of the front and back, and always compare it with the light ink of the product on the back, so as not to affect the quality of the product due to heavier printing or lighter printing. For the products with puzzle pictures on the other pages, try to allocate them on the same machine and equipment, and pack and print on the same trip, otherwise, it will cause serious quality accidents.

3. The color sequence distribution is unscientific, the key point is the color sequence distribution of multi-color offset printing machines.

4. The printing paper itself has serious color cast.

5. The blank space on both sides of the printing plate is seriously dirty, resulting in a mixed color situation (mostly seen in semi-satellite offset printing machines).

To properly grasp the balance of ink strokes, pay attention to the PH value of the wetting liquid. Under the same ink volume, too much water and too little water will affect the depth of the color. liquid volume.

6. When changing the color, the ink roller cannot be washed cleanly.

Depending on the quality of the paper, determine the frequency of cleaning the blanket. If the quality of the paper is weak and it is not cleaned immediately, it will also cause color cast.

7. Abnormal paper feeding.

Make sure that the paper feeding is normal. Every time the paper feeding is interrupted, the color of the product will be darker. Therefore, it is necessary to develop good habits, that is, to remove 6-8 sheets of goods when packaging and printing each time the paper feeding is interrupted, so as to prevent them from being mixed in the finished product and causing color cast.

8. The version change is not immediate.

If the printed version of the long-run product is found to be stenciled, it should be replaced immediately. The ability of the flower plate to absorb printing ink is reduced, which will also cause the depth of the product impression and produce color cast.

9. The person who signed the sample evaded responsibility.

Under normal circumstances, the signer must sign the sample in a short period of time to reduce the occurrence of color cast.

10. Unbalanced ink strokes.

When calibrating the light ink, it is necessary to ensure that the light ink basically conforms to the sample before printing can be started. One-sided emphasis is placed on the production volume. Usually, printing starts when the distance between the ink color and the printed sample is relatively large, which will inevitably cause a large color difference between the front and rear printed products. The correct operation should be: after the printing plate is proofread, try the master paper to calibrate the light ink, and when the trial printing sample basically conforms to the printing sample, it can be printed normally.