Car Fillers & Auto Body Fillers

For a permanent and professional repair, the answer is no. Body filler must be applied directly to a properly prepared bare metal surface. Paint provides a weak, unstable foundation that will prevent the filler from bonding securely to the steel or aluminium underneath. Applying filler over paint will almost certainly lead to future peeling, bubbling, or cracking as the paint itself lifts away from the metal.

The correct procedure is to always sand the area down to clean, bare metal. We recommend using 80-grit sandpaper to remove all paint and create a coarse, scratched surface that gives the filler a strong mechanical grip for maximum adhesion and a truly durable, long-lasting repair.

Body filler should not be applied over primer. The correct and essential order of operations for a lasting repair is Metal > Body Filler > Primer > Paint.

Think of it this way: the filler’s job is to shape the repair on the bare metal, while the primer’s job is to seal the porous filler and the surrounding metal, creating a perfect, non-absorbent surface for the topcoat of paint to adhere to. Applying filler on top of primer reverses this process, creating a weak foundation. For tiny pinholes or minor scratches in the primer itself, a very thin layer of glazing putty is the correct product, but for all standard shaping and dent repair, the filler must go on the bare metal first.

Pinholes are usually caused by trapped air or overworking the material. To minimise this, mix your filler thoroughly but carefully to avoid whipping air into the paste. When applying the product, use firm pressure with your spreader to ensure it is pressed fully into the surface. If you do encounter minor pinholes, a thin layer of finishing auto putty filler will easily bridge these imperfections before you apply your primer.