Causes and Solutions of Color Changing Faults in Gold and Silver Ink Printing

Ink and printed products lose the color of gold, making the colors grayish black and dull, which is a common failure in gold ink printing. Gold ink is a printing ink prepared by brewing gold powder. Gold powder is a mixed metal powder composed of copper powder and a small amount of zinc powder and aluminum powder.

As the chemical properties of gold powder are generally not stable enough, the acid and alkali are encountered. Gases such as carbon dioxide and sulphide produce varying degrees of chemical changes. There are many reasons for the discoloration of gold ink. In order to ensure the quality of printed gold products, effective measures must be taken in the preservation and printing of gold ink to prevent the discoloration of gold ink. Generally, the following issues should be noted:
1 The powder should not be exposed to the air during storage. Otherwise, it will react with air and water vapor to cause a chemical reaction and discoloration.

2 Gold ink is printed on non-coated paper. If it is exposed to high humidity, chemical ink, sulphides in the pulp, and barium sulfate in the filler will cause the black ink to become black, so pay attention to the control environment. humidity.

3 domestic coated paper, offset printing paper gold is particularly easy to black, the reason is the use of acid papermaking process, paper with a certain degree of acidity, not only discoloration of gold powder, and even cause toner disappear.
4 The porcelain and ink must be used for the containers and rods that make up the gold ink. Wood products, can not use metal products.
5 The auxiliary materials for deployment of gold ink should use neutral substances, and auxiliary materials with acidity should not be used.
6 do not stack too much gold semi-finished products, otherwise the heat released by gold ink drying process on the paper is not easy to disperse in time, it will accelerate the oxidation and discoloration of gold ink.

7 roller is not adjusted well. Uneven pressure, poor performance. In the printing process, the ink is piled up, so that the gold powder stays on the rubber roller. After long-term friction, the gold powder is easily oxidized and discolored.

8 After cleaning the ink fountain and the ink roller, the organic solvents such as gasoline and kerosene have not been completely evaporated, so the golden ink printing will cause the gold ink and the solvent to act and cause discoloration.

9 printing machine speed should not be too fast. otherwise. The friction of the ink roller increases, and the heat generated increases, causing the gold ink to oxidize and turn black.

10 When the offset printing ink is used, the acidic wetting liquid will come into contact with the gold ink to cause a chemical reaction and darken the metallic gloss of the print. Generally, a wetting liquid containing an alcohol is used instead of the acidic wetting liquid.