Q.
The inside of my stainless steel cookware has discolored to a rainbow color.
A.
This phenomenon occurs when ions, iron, and copper in the water adhere to the surface due to evaporation, causing a rainbow-like appearance. It is more likely to occur in relatively new conditions, and the product itself has not discolored (deteriorated), so please use it with confidence.
To remove discoloration, add 10% citric acid (or vinegar) solution (10 parts water to 1 part citric acid) and boil for about 10 minutes. After leaving it for about an hour, wash it with dishwashing detergent for effective results.
