1. Gold foil will turn black after oxidation

Pure gold foil is not easy to appear oxidation blackening phenomenon. The phenomenon of oxidation blackening is imitation gold foil, which is common copper foil. The properties of copper foil are unstable, and it is easy to oxidize and blacken in high temperature and high humidity environment. Therefore, how to delay the oxidation of copper foil and increase its life is the most important thing. First of all, before sticking the copper foil, the bottom blank must be completely dry, and the sealing primer should be thick enough. Secondly, after the copper foil is pasted, the gold foil protective paint should be applied immediately, which is very reasonable for increasing the service life of the copper foil.

For example, it is not smooth enough to touch. There are two main reasons for this phenomenon: (1) the base slab or primer at the gilding position is not in place, the bottom slab is uneven and there are many sand hole particles. Before the primer is made, the bottom slab must be covered with ash smoothly, and the sand hole shall be filled and the particles shall be removed. If the air dust is large when the primer is made, the sandpaper shall be used to grind each primer.(2) When cleaning the foil, the broken foil is not cleaned. After spraying the protective paint, the broken foil will be caught in the varnish, which is more prickly to the touch.

Brush printing due to the concentration of glue is a little thick, the bottom blank is relatively smooth, so it is easy to produce brush marks by using the brush to hit the glue. The main reason for the sagging is that the glue is too much, and the sagging is not collected with the brush immediately, which is easy to appear after foil pasting.