Copper can oxidise over time, leading to a greenish discolouration known as verdigris. This oxidation is natural and can occur on a copper tongue scraper. However, it can be avoided or reduced by carefully drying the tool after each use and storing it in a dry place. If oxidation does occur, it can be easily removed by soaking it in white vinegar or lemon juice, then rubbing it gently with a soft brush or cloth.