What's the difference between a pre-wash and shampoo? and what is a pre-wash to begin with? Well, a pre-wash is just a process that’s done before a contact wash to break down and remove any loose dirt or grime. Over time, the surface of a car will build a layer of dirt and grime, otherwise called contaminants. When you hand wash a car before pre-washing, you run the risk of scratching the paint by rubbing the contaminants into the paint. Now, these scratches may not be visible at first, but over