Analysis of color fading and discoloration
12-25-2020 10:11:06

The first point: ink in the drying process of penetration and oxidation of conjunctiva formation of discoloration.

Printing ink in the drying process will also have a certain color change. In the printing process of book printing China, the newly printed ink is darker than the ink after drying, and the ink color will be relatively shallow after drying. In this case, the discoloration is not caused by the poor light fastness of the ink, but mainly due to the penetration and oxidation of the conjunctiva during the drying process. The ink of relief printing is mainly based on penetration drying. In the drying process, the binder in the ink will penetrate into the paper fiber to a great extent. After oxidation conjunctiva drying, it will become light, which is an inevitable phenomenon. Therefore, when we print, we usually make the ink tone darker than the original proofing ink, so that it can meet the requirements of sample ink color after drying.


The second point: the ink itself caused by light fastness fading.

All inks will have varying degrees of fading in book printing China, discoloration, just compared to the strong and weak. This requires us in the actual inking work, should try to choose better light fastness ink, dark ink fade slowly, light ink fade fast. Therefore, we should not only consider the light fastness of the diluted ink, but also consider the consistency of the light fastness of several inks used for blending.


The third point: the pH of the paper itself caused by the discoloration.


Our ideal pH value of paper is 7, which is neutral. In this case of perfect paper, the above two points on the discoloration of printed matter belong to our controllable situation, we can according to the depth of color matching, pay attention to the relative proportion of ink and so on to try to make the printed matter appear perfect. The acidity and alkalinity of the paper will determine whether the printed matter can be used in the end. The pH of raw material paper is less than 7, it is acidic and more than 7, it is alkaline. Acidic paper, will affect the printing ink drying speed, will also affect the color of the ink itself. Because acid substances can inhibit the drying of imprinted oxidation conjunctiva, the ink drying on this kind of paper will be particularly slow. The same paper with strong acid will cause the ink to change color due to the weak acid of the bucket solution. Therefore, under the influence of these two factors, the final state of the printed matter after complete drying can be imagined in book printing China. The alkaline paper has a greater impact, in short, the ink acid resistance is poor, alkali resistance is worse. Basically all ink will fade or change color when it comes to alkali.

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