@chrisfixit: How do you know when you need to clay bar your car??? In todays quick tip I show you a simple method on checking to see how “contaminated” your paint is… I call it the sandpaper test. You can hear a huge difference between the clayed panel and the dirty panel. Using a clay bar does micro-scratch the paint (swirl marks) so following up with a polish and then a wax or sealer is recommended. In this case I will clay, polish, clean with alcohol and ceramic coat!