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How to: Prevent and Fix Staining
or Plastic Bleed-Through on a Car Paint Surface

How can I fix a yellow-brown discoloration in my car paint?

Staining or plastic bleed-through is a common issue when painting your car. It can be repaired by allowing the finish to cure thoroughly, sanding it, and applying a two-component undercoat and refinishing.

In this article, I’ll answer common questions about how to prevent staining or plastic bleed through and eliminate it when it happens.

  • What is staining or plastic bleed through?
  • What causes staining or plastic bleed through?
  • How can I repair a surface with staining or plastic bleed through?
  • How do I prevent staining or plastic bleed through?
  • Are there other things about using two-component surfacers and sealers I should be aware of?

What is staining or plastic bleed through?

It’s a yellow-brown discoloration in a car finish over areas repaired with polyester body filler or glazing putty.

What causes staining or plastic bleed through?

It’s caused by one or more of the following:

  • You used too much or too little hardener in the putty or filler.
  • You did not mix the putty or filler components well enough.
  • The body filler hardener has expired and is not catalyzing properly.
  • You applied a surfacer, sealer, or finish before the putty or filler had enough time to cure.
  • You applied undercoats or finishes that were too wet.
  • You applied a clear coat to white or light color without using a stain-free body filler.

How can I repair a surface with staining or plastic bleed through?

Take these two steps to repair this condition:

  1. Allow the finish to thoroughly cure.
  2. Sand the affected area, followed by applying a two-component undercoat and refinishing.

How do I prevent staining or plastic bleed through?

Here are some things you can do to prevent it from happening:

  • Always use the correct amount of body filler hardener.
  • Make sure the body filler has not expired (1-year shelf life)
  • Mix all the components thoroughly.
  • Allow the putty or filler to cure thoroughly before applying the finish.
  • Apply undercoats and finishes in a medium-wet to wet coat spray setting and always allow the proper flash time between each coat.
  • Use a non-staining body filler, especially when clear coating light colors.
  • If you believe the filler, you are using might stain or bleed through, apply a two-component surfacer and sealer.  Allow them to dry, then apply your finish.

Are there other things about using two-component surfacers and sealers I should be aware of?

  • Two components — acrylic urethane primer surfacer and acrylic urethane sealer —can stop most body filler staining problems. Both are required and must be allowed to fully cure for maximum stain resistance.
  • To be completely sure that body filler staining does not happen, use a non-staining body filler, and follow the manufacturer’s recommendations.

Taking these steps will prevent the staining of body filler bleed through on your car surface.