1. Ink discoloration after high temperature baking
Iron printing ink belongs to heat curing ink. One of its technical requirements is that the color of the ink remains unchanged after baking at high temperature. However, in practical consumption, some color inks are more or less discolored after baking, for example, white ink, diluted ink and ink distributed with a large number of white ink and diluted ink. These inks will yellowish after repeated baking, especially the spot color inks distributed with a large number of diluents, and the color will change greatly after repeated baking. For example, light blue specialty, which is participated in by a large number of diluents in the distribution of blue ink, may become dark blue specialty after repeated baking. Technological planners should give full consideration to the formulation of printing technology, and try to put these Beijing baked and discolored ink in the final printing.
2. Color change before and after polishing
The last process of printing is polishing oil. The purpose of polishing oil is to maintain the pattern and avoid damage. The second is to improve the gloss and beauty. Generally speaking, the printing polish will yellowing after baking at high temperature, and the reflectivity of the polishing oil layer to light will be greater, so the color of the ink after polishing will generally be brighter than before polishing. However, some polishes contain whitening agents, which show blue under light. Therefore, after polishing with this polish, the ink color will be bluer than before. The overall color phase is the superposition of the ink color and the light oil bluer.
3. Color Change of Metal Spot Color Ink after Oxidation
Printed iron, gold and silver inks are colored by metal powders such as gold and aluminium. Among them, iron-gold ink is a printing ink made of grinding copper powder; iron-silver ink is an ink made of grinding aluminum powder. The chemical properties of gold and silver powders in iron and silver inks are generally not stable enough. When acid, alkali, water vapor, sulfide gas and carbonate gas are encountered, chemical reactions will occur, resulting in a lack of metallic color in ink. Among them, the discoloration of metals changes from golden yellow to brown red, and then to black. Because copper can produce red cuprous oxide when it is first oxidized, it will turn into black cuprous oxide when it is further oxidized. In addition, gold powder is easy to turn into basic cuprous carbonate when it contains more carbonate gas and more humidity, so the gold ink on the printed products gradually darkens. Silver and ink turn grey after discoloration, lacking the silvery metallic texture.
4. Different Thicknesses of Printing Ink
We know that the same ink has different printing thickness and different color. In practical printing, the thickness of ink layer is controlled by printing pressure and ink quantity. Generally speaking, the printing pressure can not be changed after adjusting reasonably. Therefore, the thickness and evenness of ink layer in printing are accomplished by controlling ink quantity. Most of the domestic iron printers still rely on manual adjustment of ink feeding screw to control ink feeding. Because artificial conditioning is affected by many factors, the printing ink may be uneven thickness, ink color will be different, color and standard color manuscripts are different.
In practical consumption, the above factors affecting the color change of printing ink will be encountered, which requires operators to understand and control the changing rules of these factors, and then according to the actual situation, allocate the appropriate proportion of ink, formulate a reasonable printing process, reduce the color change of repeated printing ink, which is conducive to saving downtime and improving consumption efficiency. In the field of Shanghai Printing, Shanghai Haohe Printing concentrates on providing brand service to customers with professional printing design. In every detail about printing, we adhere to the service concept of "every step, the first thing we think of is customers", striving to control the cost to the minimum under the premise of guaranteeing quality. Work is also the fundamental work that any iron-printing enterprise should pay attention to and constantly grasp.
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