• Sources of error:
  • Base material not properly dried through.
  • Use of sandpaper that is too coarse.
  • Sanding technique of the user.
  • Machine „beats“ when turning.
  • The layer thickness of filler was too low for previous sanding work.
  • Scoring in the substrate may also be caused by previously unremoved scoring on the metal surface.
  • Paint structure applied by the wet-on-wet method. Reduced film thickness allows the substrate to „push through“ more easily.
  • Filler application without intermediate sanding (wet-on-wet), which allows the surface to be „sanded“. (Prerequisite for this: complete drying).
  • Sanding paper selected too coarse.
  • Sanding too aggressively.
  • Sanding only in one direction (With the sanding block only from e.g. right to left).
• Error prevention:
  • Process material according to technical information.
  • Select finer abrasive paper for final filler sanding.
  • Carry out final filler sanding with contrast powder.
  • Adapt layer thickness to the substrate. But do not overcoat!
  • Allow material to dry properly.
  • Adapt filler system to substrate.
• Repair method:
  With uni basecoats, you can still salvage something with this mistake. At this point, the surface is sanded down with a block and finished. This can be used to „cover-up“ sanding marks in uni materials.
  Unfortunately, metallic basecoats cannot be visually salvaged. Here, the surface can only be sanded and repainted.

1. Build up substrate with sanded old coating.
2. Substrate
3. Roughness depth with correctly used abrasive grit can cover the following material.
4. The roughness of a too coarse abrasive grit.
5. Filling of a too deep grinding groove created by too coarse abrasive grit.
6. Incidence of light.
7. Light reflection.
8. Metallic basecoat.
9. Clear lacquer.
10. Last possible finish zone.
11. sanded old material.

As you can see from the graphic, reflections in sanding marks with metallic basecoats cannot be eliminated. The light refracts in the metallics and is reflected out of the deep sanding marks. Thus, sanding marks become more visible than they already are.

1. Build up substrate with sanded old coating.
2. Substrate
3. Roughness depth with correctly used abrasive grit can cover the following material.
4. The roughness of a too coarse abrasive grit.
5. Filling of a too deep grinding groove created by too coarse abrasive grit.
6. Incidence of light.
7. Light reflection.
8. Uni basecoat.
9. Clear lacquer.
10. Last possible finish zone.
11. sanded old material.

Reflections in sanding marks with solid basecoats can be eliminated with a little help, as you can see from the graphic. The light refracts in the deep tracks and is only reflected out of the deep sanding tracks in a single color. Thus, sanding traces are not perceived in this way. The „dip“ in the sanding marks can be eliminated by a well-executed finish.