Many types of surfaces require an undercoat before the final coat of paint can be applied. Without an undercoat, paint may fall off or chip over time. Primer is another name for an undercoat, and there are many steps to applying it to make sure your paint will stick.
• Step 1: Sand your painting surface. Remove any old paint chips or rust with a scraper and fill any holes.
• Step 2: Clean your painting surface with a warm and soapy dish rag and allow the surface to dry.
• Step 3: After the surface has dried you can then apply an undercoat. If this coat dries thin or in a way that still reveals the surface underneath, apply a second coat and let it dry.
• Step 4: Apply the final coat of paint.
Surfaces That Require an Undercoat
An undercoat can be applied to any surface that needs to be painted, but it should not be used as the last coat. Surfaces like plastic and metal must have an undercoat or the paint will fall right off. Sometimes primer is used to cover a dark surface. For example, if the surface is black and you want to paint it white, the undercoat will help cover up the black so it doesn't show through.