Next, Park sprayed two coats of DuPont 2804s high solids urethane sealer. Sealers perform many functions. They act as a barrier between the new and old paint preventing swelling and lifting, they are also an adhesion promoter, and they make the car a uniform, neutral color. This is important when doing a color change like we are. If our metalwork was superstraight, we could topcoat directly over the sealer without an additional layer of primer. And since paint is semitransparent, painting over a neutral grey background would ensure even color over the whole car.