Effect of paper acidity and alkalinity on printing quality
The printing process requires the pH of the paper to be neutral. However, due to differences in sizing materials, filler properties, and color composition during paper and pulping, the paper may be either acidic or alkaline. For example: Vaseline sizing is used in the papermaking process. There are certain residual chlorine and organic acids in the slurry. If the paper is not properly processed, the paper will be acidic; caustic soda (NaOH) is used in the process ), As well as alkaline fillers and colorants, residual lye in the slurry, etc., without the necessary treatment, the resulting paper will be alkaline. Dinosaur Island Toys Shantou Chenghai Sweet Baby Toys Firm , https://www.sweetbabytoys.com
Acid paper will inhibit the drying of printed ink. The stronger the acid, the slower the ink drying speed. There is an example of printing cigarette packs to a cigarette factory at the same time, the same ink, the same offset press, two different types of coated paper, however, the drying speed is very different. Afterwards, he contacted the coated paper factory and analyzed the manager. The reason for the slow drying of the coated paper was that the paper fillers and rubber compounds 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 printing ink. The acidic paper inhibits the printing ink conjunctiva. When the pH value of the paper is reduced from 5.5 to 4.4, the ink drying speed is slowed by three times. The paper is acidic and also affects the color of the printed product.
Paper that is alkaline is generally mistaken for faster ink drying. In fact, the effect is not obvious, but it is faster, and it is not directly proportional. In relief, intaglio, and screen printing, the acidity and alkalinity of paper only affect the speed of ink drying. For offset printing, the acidity and alkalinity of paper not only affects the drying of ink. Because the offset printing hopper 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, the alkaline substances in the paper will be neutralized with the acidic components in the water during the printing process, affecting the pH value of the fountain solution. In addition, acid paper will emulsify the ink and cause scumming.
If the paper contains free acid, the paper will be gradually eroded by the acid, reducing the durability of the paper.
When printing gold, silver and hot stamping, when the paper is acid or alkaline, it will chemically react with the metal powder, discoloring the printed and hot stamping anodized aluminum foil, and losing the original light and color.
In the printing process, the paper is preferably neutral, that is, the pH value is around 7, or slightly alkaline. For example, the commonly used offset paper, offset paper, writing paper pH value should be neutral. It is necessary to check the purchase of paper, ink and PS version. The pH of the paper can be measured with pH test paper, or with a lightning magnetic pH meter.