Apply to cool surfaces only. Ideal way to use this product is to wash the car to get rid of all the loose contaminants from the car in order to let the product work on the stuck on debris. Once that car is washed, spray the whole car down with Iron Remover and let it dwell for approximately 2-10 minutes. Once it turns a solid purple, its ready to be removed. Purple indicator is the chemical reaction taking place and will vary based on the level of contamination. Rinse and re-wash the car with your soap solution. Make sure to thoroughly rinse away any iron remover. Same process on the wheels. This product is PH balanced so it is safe on all painted surfaces and glass. Dwell time: 2-10 minutes