Because ceramics contain impurities, the color of whiteboard is not particularly white and bright. The raw material for firing ceramics is kaolin, and its main components are SiO2 and Al2O3. Ceramics fired with high-purity kaolin have high whiteness and purity, so they are whiter and brighter. However, if it contains impurities such as FeO, Fe2O3 and TiO2, it will have a poor appearance and will not cause harm to human body. However, some people deliberately mixed some other ingredients in order to achieve a certain effect. This situation is another matter.