K.C. Body Shop Supply

Call Us (773) 306-2805

How to: Prevent and Repair Shrinkage in a Car Paint Finish

How can I remove sand scratches or feather edges in my car paint?

You’ve finished painting your car. However, within hours, days, or weeks of the paint drying, you notice feather edges or sand scratches in the repaired area. This is shrinkage. Repair it by sanding and refinishing the affected area.

In this article, I’ll answer common questions about how to prevent shrinkage and eliminate it when it happens.

  • What is shrinkage?
  • What causes shrinkage?
  • How can I repair a surface showing signs of shrinkage?
  • How do I prevent shrinkage?

What is shrinkage?

Paint shrinkage (also known as bullseyes, ringing, or edge mapping) happens when the final coating of paint shrinks, revealing ragged edges and scratches.

What causes shrinkage?

Shrinkage in a paint finish can be caused by several things:

  • You applied the final coat of paint before the undercoats dried or cured.
  • You used very wet undercoats and did not allow enough flash time between each coat.
  • Your undercoats were under-reduced.
  •  You used a poor-grade or too-fast evaporation thinner of reducer for the spray conditions.
  • You applied the finish over body filler that was not dry or cured.  
  • You used a solvent cleaner that was too strong or a thinner or reducer as a surface cleaner. GLM800 Pre-Paint Cleaner is a fast-drying solvent that should be used just before applying a new finish. It’s not too strong or too weak, it’s just right.

How can I repair a surface that shows signs of shrinkage?

Do either of the following things to repair an area with shrinkage:

  • Allow the area that shows shrinkage to completely dry and cure, then sand and refinish.
  • If more filling is needed, apply a primer surfacer such as GLM2000 2K Urethane High Build Primer.  Sand smooth, and refinish.

How do I prevent shrinkage?

Allowing enough drying time and curing time is critical when it comes to preventing shrinkage. Here are five things to remember:

  1. Allow undercoats to completely dry and cure before sanding and painting.
  2. Thin or reduce undercoats following the instructions on the product labels. Then apply in thin, wet coats, allowing enough flash time between coats to avoid bridging scratches.
  3. Choose the right thinner or reducer based on the temperature, humidity, air movement, and the size of the repair. Learn how to select the right thinner or reducer for different weather conditions. Choose a Gleam Automotive Finish Reducer depending on your spraying and drying conditions.
  4. Follow the body filler manufacturer’s recommended cure time.
  5. Use a solvent cleaner designated for either a lacquer soluble or cured enamel or urethane insoluble substrate.

Following these steps will help prevent shrinkage on the finish of your newly painted car.