The paint you see, the top coat, is often part of a paint "system" in which the parts combine to give a decorative long lasting, hard wearing protection to the surface beneath. Commonly, a paint system will include two or more of the following components:

Primer: Prevents corrosion, adheres to and penetrates the surface and provides a sound key for the next coat.

Sealer: Prevents contaminants coming to the surface and prevents other coats sinking in to the surface.

Undercoat: Hides the previous colour, fills minor imperfections, gives a uniform surface, sands easily and promotes adhesion.

Top Coat: Provides the primary protection layer and decorates. Which Paint Where?

Filler: Used to fill imperfections and level the surface.