How do you think clay works?

There are only two ways to remove contaminants from the surface of a car. One is to use some kind of chemical which breaks down the dirt. Soap, which is a surfactant, and water remove contaminants chemically. Simple green is a chemical that will remove contaminants . . . . but I wouldn’t use it to wash my car. (Simple Green is fine on wheels and tires but not paint.)

The other way to remove contaminants is abrasion. You physically rub the contaminant off. The abrasive substance can be very mild to very harsh. A very harsh abrasive substance would be the powder cleanser that you use to clean your bathroom tiles. (Steel wool cleans by abrasion. So does sandpaper.) I wouldn’t use bathroom cleanser on my car’s hood! Clay – though a very, very mild abrasive – is still abrasive. It might take a while, but if you use it enough times it will remove paint.