If the ink can be fixed well, it is dried from the inside out. In this case, although the ink surface can resist static pressure after solidification, the ink layer should not be able to withstand friction.
Ordinary inks used for offset printing are mainly dried by chemical reaction. The oxidation and high polymerization of ink rosin are the functions promoted by the desiccant and are important components of the ink.
If the ink is not dry enough to resist the pressure of the next printing color, the paper cannot print the second color.
The worst part is that if the ink takes a long time to dry, the rosin-containing medium will penetrate into the paper excessively and the lack of the ability of the ink film to bind the pigment may cause white deterioration. Operators should know that this trouble is very complicated, and its generation is based on unbalanced factors such as ink, paper, and printing conditions.
Remedy
1. temperature
Since drying is a type of chemical reaction, air temperature can affect its drying speed. Control the temperature of the paper or printing room if it is under abnormal conditions. From 60? V less 0? Is the most ideal.
2. Desiccant
If the amount of desiccant in the ink is not enough, pay attention to its characteristics and amount, add some desiccant to the ink. However, adding too much desiccant is not recommended.
3. Control wetting moisture
Too much moisturizing water will cause this trouble.
4. Moisture of paper
Too much moisture in the paper will slow down the drying process. In this case, it is best to strengthen the desiccant.
5. PH value of sink
Too much acidity (low pH) of the moisturizing water will reduce the desiccant activity. The suitable range of PH is from 5.0 to 6.0. At least, the PH value should be maintained above 4.5.
6. PH value of paper
For the same reasons mentioned above, it is very dangerous for the PH value of paper to be too low. When the pH of the paper is too low, such as less than 4.5 in non-coated paper and less than 6.0 in powdered paper, it is necessary to use strong desiccant or more common amount of ordinary desiccant.
7. Ingredients of the sink liquid
It is known that some of the synthetic chemicals in the water bath can have an adverse effect on the drying rate.
8. Varnish
If you find that you have trouble after finishing all the printing, you have to reprint with varnish.
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