1.  The basic composition of gold offset printing  ink
Bronze powder  30～50%
Gold color Offset printing  oil 70～50% mix the bronze powder with gold Oil homogeneously can become gold ink.

2. The Causes and Preventive measures
①The pH of the paper. Due to improper treatment in the process of pulping and papermaking, such as organic acid in the pulp or residual chlorine in bleaching, the paper will become acidic, and alkaline based filler and pigment will make the paper alkaline. If the paper is acidic, the acidic paper will play a role in inhibiting the drying of imprinted oxidation conjunctiva, making the drying speed slow; while for the paper with too strong alkalinity, the alkaline substances in the printing process will be continuously transferred to the bucket liquid, which will neutralize the originally weak acidic fountain solution, affecting the normal pH value of the fountain solution and causes the remaining ink discoloration deterioration, in addition, will make the ink emulsion, causes the floating dirty. Therefore, the best paper pH value is  7 to  avoid the discoloration issue.

②Fountain solution pH value and ink balance. In offset printing based on the principle of hydrophobic part of printing plate and hydrophilic principle of non graphic part, the acid substance in the fountain solution can cleaning and remove the dirt. However, if the acid is too strong, the gold printing  will be changed color and lose its metallic luster, resulting in printing plate pattern, slow drying of imprint and sticking on the back. If the acidity is too weak, the picture and text on the printing plate will be dirty and paste. Therefore, the general fountain solution pH value control in 5 ~ 6 is appropriate. Water ink balance is to use as little water as possible on the premise that the printing plate is not dirty and paste, so that the emulsification of the ink is controlled within the minimum range of 25%. Because the water is too much, it is easy to cause the printing gold ink color is too light, the gold ink is dull, the color is not bright, the gold ink is emulsified, the paper stretch deformation causes the overprint inaccuracy and other quality defects; too little of water, easy to make the page dirty, greasy and the emergence of parallel paste, so it is very important to master the balance of ink and water. In addition, the intermediate roller must be separated from the ink path and waterway system, which is also an essential method to avoid.

③Printing speed. If the printing speed is too fast, it is easy to produce intense rubbing between the rollers, and then the heat generated will change the color of the ink. The general experience is that it should be controlled at 5000 sheets per hour.

④Oxidation of bronze powder. Bronze powder has the disadvantage of easy oxidation and discoloration, so the bronze powder must be kept in closed air as far as possible, and the storage time should not be too long.

⑤PH value of gold blending oil. Bronze powder is easy to oxidize, so the gold adjusting oil used must be fast drying and fast solidifying resin oil with low oxidation property and neutral pH value. In order to avoid oxidation due to long-term storage, it is better to use the self-adjusting method to further improve the oxidization issue.

         Excerpt from CNKI