Candy cans are usually polished. Common tin cans are coated with varnish and sub-varnish. Varnish is a synthetic resin. Nowadays, varnish usually refers to varnish with transparent surface, which is made of base material and additives without adding any pigment. Shiny after film formation, commonly known as varnish. There are two kinds of varnish: UV varnish and PU varnish. UV varnish is used in the production of canned candy. In the candy tin box produced by Guangzhou Boxin, the function of varnish can be divided into two types: 1. As a transparent protective paint, its hardness and wear resistance are better than that of colored paint, which can protect candy tin boxes from being polluted by varnish; 2. As a hand painting, it not only has better luminosity and brightness, but also has better hand feeling. Varnish can make candy cans brighter. Matt oil is relative to gloss oil. Compared with varnish products, oil separation products have better friction reduction effect of tin cans because of their rough performance, and can also better protect gloss paint from being scratched and prevent candy tin cans from producing dark flowers.