Primer

Primer is a preparatory coat applied before any color paint goes on, and it does two jobs at once: it gives paint a consistent surface to grip, since bare plastic, resin, and filler can all take paint differently, and it reveals flaws like leftover flash, sanding marks, or a sunken seam that were invisible on raw plastic but show up clearly once everything is one flat color.

Choosing a primer color affects the paint that follows. A grey or white primer is a neutral base for most color schemes, while a black primer is popular under dark camouflage or metallic finishes since it deepens shadows and can make metallic paint look more convincing when a little of the dark base shows through. Primer is typically applied through an airbrush for an even coat, though rattle can versions exist for builders without one.

A common mistake is priming over a seam that has not fully cured or been checked closely, since the primer coat itself can be the moment a hidden flaw finally becomes visible, requiring another round of filling and re-priming before color paint can go on. Applying primer too thickly is another frequent issue, since a heavy coat can hide fine surface detail almost as effectively as it reveals larger flaws.