Sanding marks

Sanding marks in the substrate show as lines in the surface of the refinish paint.

Causes

1. The substrate was sanded with an abrasive that was too coarse. The paint shrinks more strongly in the sanding marks because of the higher film thickness
2. The drying times for the undercoat materials were not observed correctly: The sanding marks are clearly visible due to the swelling of the undercoat materials at the time of painting and the sinkage after drying
3. Filler and topcoat layers were applied too thin to cover the sanding marks in lower layers
4. Wrong sanding technique and/or sanding machines used

HOW TO AVOID

1. Use specified grade of sanding paper (P80/P150 for body filler, P240 for primer filler/filler – see relevant technical data sheets). Use guide coat for sanding.
2. Keep to recommended drying times.
3. Keep to recommended film builds.
4. Place sanding machine on surface of paintwork before starting the machine. When dry sanding filler coats, the eccentric stroke should not be greater than 5 mm.