How To Troubleshoot Automotive Paint: Causes and Cures

Automotive Paint Troubleshooting Causes and Cures

Through the years the du Pont organization has met and solved practically every automotive refinishing problem that can be imagined. In the interests of better refinishing du Pont has made the following information available.

Shrinking and splitting of primer-surfacer

Cause:

  • Improper cleaning of surface.
  • Improper “feather-edging” broken area.
  • “Piling on” in heavy coats.
  • Insufficient drying between coats.
  • Fanning air to force drying.
  • Applying on cold surface.

Cure:

  • Use clean rag wet with Prep-Sol to remove wax, polish, and grease. Where bare metal is exposed, sand bright and treat with a metal conditioner.
  • “Feather-edge” old finish about 2″ to 4″ back from edge of spot, finishing up with No. 400 sandpaper to avoid deep scratches.
  • Apply in medium wet coats.
  • Allow solvents to “flash” off before applying succeeding coats. Let last coat dry 30 minutes before sanding.
  • Do not fan air to force drying — it causes surface drying and traps thinner which penetrates scratches in old finish.
  • In cold weather, make sure the metal, the primer-surfacer and the shop are approximately the same temperature.



Overspray—Dry spray

This condition is usually found where the finish forms a center line on cowls and turret tops. If left side of car is painted first, overspray appears to left of center line when right side is sprayed—or vice versa. At this point, gun is held at angle and farther from surface than at other points of stroke.

To overcome, spray side of car on which overspray appears with a wet mist coat. A mist coat is made by adding several parts of thinner to the color left in the cup, or it may be a straight coat of a good thinner.

Orange peel

Cause:

  • Improper atomization.
  • Sprayed improperly.

Cure:

  • Use recommended air pressures at the gun and follow thinning instructions.
  • Use arm in full, long strokes, paralleling surface with as little wrist action as possible. Hold gun at right angle to and from 6 to 10 inches from surface.
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