Analysis of the effect of paper pH value on printing quality of book

Analysis of the effect of paper pH value on printing quality of book

The paper is preferably neutral during the printing process, that is, the pH value is around 7, or slightly alkaline. For example, the pH value of coated paper, offset paper and writing paper commonly used in offset printing should be neutral. It is necessary to close the purchase of good paper, ink and PS version. The pH value of the paper can be measured by pH test paper or by a lightning magnetic pH meter.

The printing process requires the pH of the paper to be neutral. However, due to differences in the composition of sizing materials, fillers, and colorants during the pulping process, the paper may be either acidic, or the printing process requires the paper to be pH neutral. However, due to differences in the composition of sizing materials, fillers and colorants during the pulping process, paper may be either acidic or alkaline. For example: Vaseline is used for sizing in the papermaking process. There are certain residual chlorine and organic acids in the pulp. If proper treatment is not carried out, the paper produced will be acidic; caustic soda (NaOH) is used in the papermaking process. ) and alkaline fillers and colorants, residual lye in the slurry, etc., and without necessary treatment, the resulting paper will be alkaline.

Acidic paper will inhibit the drying of printing ink. The stronger the acidity, the slower the ink drying speed. There is an example of printing cigarette packs for a cigarette factory at one time, the same ink, the same offset press, and two different coated papers, however, the drying speed is very different. After contacting the coated paper factory, the manager analyzed that the reason for the slow drying of the coated paper was that the paper filler and rubber contained acidic substances, which caused the coated paper to be acidic. The acidity and alkalinity of the paper have a decisive influence on the printing process and the drying conjunctiva of the printed ink, and the acid paper inhibits the conjunctiva of the printed ink. The ink dries three times slower as the paper pH is lowered from 5.5 to 4.4. The paper is acidic, which also affects the color of the printed product.

The alkalinity of paper is generally mistaken for speeding up the drying of ink. In fact, the effect is not obvious, but it is faster, and it is by no means proportional. In letterpress, gravure, and screen printing methods, the acidity and alkalinity of the paper only affect the drying speed of the ink. In offset printing, the acidity and alkalinity of the paper not only affects the drying of the ink. Because the offset printing water bucket solution is not pure, there are acidic substances with cleaning ability such as surfactants and wetting agents. If the pH value of the paper is higher than 9 at this time, the alkaline substances in the paper will be neutralized with the acidic components in the aqueous solution during the printing process, which will affect the pH value of the fountain solution. In addition, the acid paper will emulsify the ink, resulting in the phenomenon of floating.

If the paper contains free acid, the paper will be gradually eroded by acid, reducing the durability of the paper. When printing gold, silver and hot stamping, the acid and alkali of the paper will react chemically with the metal powder, so that the imprinted and hot stamped anodized aluminum foil will change color and lose its original brightness and color.

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