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.