Automotive Paint Bleeding usually occurs when your topcoat appears to have a discolouration in appearance. In most cases this occurs when a new topcoat has been applied and the solvent dissolves pigment that is soluble in the existing finish. Paint Bleeding has an appearance of a spot like discolouration of the topcoat. The over use of peroxide hardener in polyester body fillers can result in a similar stain due to a chemical reaction with the pigment.
Common Cause
Solvent in the new topcoat being applied dissolves soluble dyes or pigments in the old paint finish. This can be common in older shades of red and maroon.
Undercoat and or Topcoat not thoroughly dry.
Over use of peroxide hardener in polyester fillers.
Insufficient mixing of putty or filler.
Prevention
Test existing paint finish by spraying a small test area.
Use a sealer/undercoat on existing paint finishes.
Thoroughly mix body filler hardener with the correct manufacturers specifications.
Ensure the sealer/undercoat is completely dry.
Repair
Bleeding can be repaired by allowing the topcoat to fully cure, then sanding down the affected area and applying an isolator or sealer over the area. Once sealed you will be ready to re-apply your colour topcoat.