why do you have to sand primed surfaces before painting?

Question

I get why you have to sand a surface before priming – it removes imperfections and creates a smoother surface. But why do you then have to sand again before painting? Surely by doing that you’re just sanding away all your primer?

In: 1

Answer 1

It really depends on what you are working on. If you are painting something and you want the smoothest surface possible when you are finished (like most pieces of fine furniture or a car), you’ll sand after every coat, whether it’s primer, paint or clear-coat. The key with sanding primer is to use a very, very fine grit sandpaper and only remove the roughness of the texture, but a very minimal amount of paint.