Gold ink printing process in book printing and other products printing process
Gold ink printing process in book printing and other products printing process
In commodity book printing, packaging and label printing , gold ink is often used to realize the printing of gold graphics and texts, and give people a feeling of delicacy, gorgeous and nobility. As a special printing method, gold ink printing is slightly different from ordinary ink printing in the use of printing raw materials and process operation.
1. Gold ink blending
Gold ink is made of gold powder, gold blending oil and a small amount of auxiliary materials. Ordinary color inks are pasted and stored in cans. Usually, gold ink is stored in two different containers with gold powder and gold blending oil, Then proportionally (usually the ratio of gold powder to gold blending oil is 1:1) prepare gold ink. At present, there is also a ready prepared gold ink supply in the market, which can be printed directly. However, when printing plants use gold ink, they should consider factors such as the amount of ink used in the layout, printing cycle and product quantity. Because the printing performance of gold ink will change and lose the original metallic luster after it is opened for 1 ~ 2 hours, gold ink is used Ink printing is best used with adjustment.
2. Gold ink printing process
Gold ink printing generally adopts neutral or neutral hard lining, and the pressure of inking roller on the printing plate cannot be too large, otherwise it will cause the phenomenon of plate pasting
Gold ink printing process in book printing. During printing, when the gold ink layer on the printing plate is transferred to the surface of paper or other substrate, there is often insufficient ink or even bottom exposure. Therefore, in order to saturate the gold ink and fully show its unique metallic luster, the secondary printing method is generally adopted. At present, there are basically two secondary printing methods: one is to print fake gold ink as the background color, and then overprint gold ink; Second, direct printing of gold ink twice. The fake gold ink used in the former method is generally mixed with transparent yellow or medium yellow ink. If the paper is loose and the flatness of the paper surface is poor, the fake gold ink is mainly medium yellow, and an appropriate amount of gold ink is added. If the paper is tight and smooth, use transparent yellow and a small amount of gold ink to prepare fake gold ink. When printing, the amount of ink in the background color shall be as small as possible, in the principle of no bottom exposure and no edge penetration. When the background ink is not completely dry, overprint the gold ink, and the ink amount can be slightly larger, so as to reach the saturation state of the gold ink. When using the latter method, it should also be emphasized that it is appropriate to overprint the gold ink for the second time when the gold ink printed for the first time is not completely dry. This is because the gold powder in the gold ink is a metal pigment. If it is printed after it is dry, its particles are not easy to stick.
3. Precautions for gold ink printing
(1) Properties of paper
The properties of paper will have a great impact on the quality of gold ink printing. The higher the smoothness and tightness of paper, the better the metal effect of printing; On the contrary, printing on paper with porous surface and rough texture will have a poor effect. In addition, the pH value of the paper surface is preferably greater than 5.5
Otherwise, when printing is stacked and stored, the sulfate contained in the paper will cause the gold powder to change color and blacken, and even cause the gold powder to be corroded and disappear.
(2) Gold ink printing
The picture and text of gold ink printing layout should not be too thin, otherwise it is easy to cause paste, and its reflection effect will become worse.
(3) Wear resistance
The wear resistance of gold ink layer after printing is an important index to measure the quality of gold ink printing. At present, there are two measures to solve the wear resistance of gold ink: one is to mix gold ink with gold adjustment oil with slightly higher viscosity, and the other is to polish with bright paste after printing.
(4) Gold ink discoloration
After the gold ink printing products are placed for a period of time, the gold powder will be invaded by sulfur, oxygen and moisture in the air, which will darken or even blacken the imprinted surface, affecting the product quality. This is what we usually call the discoloration of gold ink. We should pay attention to it in the process of printing storage.
(5) Gold ink and other color ink overprint
The gold ink printing process in the printed matter should print the gold ink on the dark field as far as possible, such as printing gold on red, blue and black, with better effect, especially when printing gold ink on purple, black and dark blue.
In addition, book printing ordinary color ink on gold ink should be avoided as far as possible. If you must print ordinary color ink on a large area of gold ink, you should first reduce the viscosity of ordinary ink, and you must wait until the gold ink is completely dry before printing, otherwise it will lead to the flower of gold ink.
