Sanding marks
Description of problem:
    The sanding marks underneath the topcoat show through.
 
Causes:         
  • Ground coat is too thick.
  • Insufficient drying time before the application of the topcoat.
  • Sand paper used is too coarse.
  • Substrates are soft, not dried enough or sensitive to the solvents present in the topcoat.
  • Too low film build.
 
Preventive measures:
  • Do not spray thick substrates.  They may be dry on the surface but still soft on the inside.
  • Leave enough flash off time between coats.
  • Use correct sandpaper grade.
  • Use solvent test to identify soft substrates (i.e. T.P.A).
  • Apply normal film thickness of the topcoat.
 
Remedy:
    Depending on the seriousness of the problem, either sand lightly with P1200, use rubbing compound and polish, or leave to dry completely, sand and repaint.

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