Necklaces made of branches and copper fade easily. In the process of long-term use, necklaces with copper and branches will have some fading problems. Copper is an easily oxidized metal. When it is exposed to air and comes into contact with substances such as sweat, it will produce oxidation reaction, which will lead to the change of surface oxide film and color. Branches are natural organic substances that secrete oil or contain pigments. These substances react with copper, which will also lead to color change. A necklace is an ornament worn around the neck. It is a pendant made of all kinds of jewels, precious stones, shells, metals, wood or other materials, and hung by chains or ropes. Necklaces can be a form of beautifying appearance, showing identity, religious significance or souvenirs.