The drying speed of different inks is also different, and the key lies in the properties of ink pigments and binders. Ink drying refers to the changing process of ink from fluid state to solid state, and its speed has a great influence on the quality of printed matter.
If drying is too fast, the ink will crust and paste on the surface of the printing plate, which will cause ink accumulation and poor gloss in printed matter; If drying is too slow, the back of printed matter may be sticky and transfer, which is not conducive to the next process.
If the ink can be fixed well, it will dry from the inside out. In this case, although the ink surface can resist static pressure after solidification, the ink layer can not resist friction.
Ordinary ink for flat offset printing is mainly dried by chemical reaction, and the oxidation and polymerization of ink turpentine are promoted by desiccant and are important components of ink.
If the ink is not dry enough to resist the pressure of the next printing color, the paper cannot print the second color.
Worst of all, if the ink needs to be dried for a long time, the medium containing turpentine will excessively penetrate into the paper, and the ink film lacks the ability to bind pigments, which may lead to white deterioration. Operators should know that this kind of trouble is very complicated, and it is based on unbalanced factors such as ink, paper and printing conditions.
Remedy
1. Temperature
As drying is one of the chemical reactions, air temperature can affect its drying speed. Control the temperature of the paper or printing room, if it is under abnormal conditions. It's best to reduce it from 60℉v by 0℉.
2. Desiccant
If the amount of desiccant in the ink is not enough, pay attention to its characteristics and amount, and add some desiccant to the ink. But it is not recommended to add too much desiccant.
3. Control the wetting moisture
Too much wetting water will cause this problem.
4. Moisture of paper
Too much moisture in the paper will slow down the drying speed. In this case, it is best to strengthen the desiccant.
5. PH value of the sink
Too much acidity (low PH) in wetting water will reduce the activity of desiccant. The suitable range of PH is from 5.0 to 6.0. At a minimum, the PH should be maintained above 4.5.
6. PH value of paper
For the same reason 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 coated paper, it is necessary to use a strong desiccant or a larger amount of ordinary desiccant than usual.
7. Composition of tank liquid
It is known that some synthetic chemicals in the sink liquid can have a bad effect on the drying speed.
8. Printing varnish
If it is found that there is a problem after all the colors are printed, it will have to be printed again with varnish.
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