Sanding Scratches

Description

Surface scratches under the paint film.

Cause

Shrinkage of the paint film during drying causes it to follow the contours of any scratches or other finishing marks in the underlying surface. The defect results from:

1. Poor finishing of the underlying surface, abrasives too coarse, inadequate flatting, inadequate stopping
2. Colour coat applied before the primer is properly hard.
3. Insufficient paint thickness, or a too slow drying rate .
4. Incorrect mixing of paint, use of wrong or poor quality thinner.

Prevention

1. Use the correct grade of abrasives, use stopper on any deep scratches, flat the surface to a smooth finish.
2. Ensure that the primer is fully hardened before applying the colour coat.
3. Apply the correct paint thickness, under correct drying conditions.
4. Mix the paint thoroughly, using only recommended thinner.

Rectification

If the marks are light it may be sufficient to flat, compound and polish the affected area. In more severe cases the surface must be rubbed down until the marks are removed and then repainted.