1. Water quality problem: the water used is hard or has high mineral content. After a period of time, water stains and scale will leave yellow marks on the ceramic ring. This is because minerals in water will remain on the ceramic surface under dry conditions, forming yellow precipitate.
2. Incomplete cleaning: the detergent used is not strong enough, or the cleaning is incomplete, and the residual dirt will gradually accumulate and form a yellow watermark. The tiny pores on the surface of ceramic ring will also absorb dirt, which is difficult to completely remove.
3. Contact with dyes or chemicals: When the ceramic ring comes into contact with the liquid containing dyes, chemicals or strong acid and alkali substances, it will be dyed or damaged, resulting in a yellow watermark.