How to Use a Fiberglass Cloth & Resin Car Repair Kit

Fiberglass is a cheap way to fix bodywork on cars. Car fiberglass kits come with a piece of fiberglass mat, resin, hardener, stir stick and small buckets. Fiberglass is a strong and durable material that will bond to almost any surface including metal, wood and plastic. Fiberglass is applied by cutting the fiberglass mat into layers that are the size of the repair. The resin, mixed with hardener, is then applied to the dry mat.

Things You'll Need

  • Coarse-grit sandpaper
  • Rags
  • Acetone
  • Fiberglass resin
  • Hardener
  • Mixing bucket
  • Stir stick
  • Felt roller
  • Air roller
  • Fine-grit sandpaper
  • Palm sander
  • Sand the surface of the repair using coarse-grit sandpaper. Scuff the entire area so it is dull and smooth to the touch. The fiberglass will not bond correctly to any unsanded surface that is left on the repair.

  • Clean the surface using a rag and acetone. Remove any dust or grease that may be left on the surface. Any grease or oil can cause the fiberglass to delaminate, which means it will not bond to the grease or oil.

  • Cut the mat to the size of the repair using a razor knife, gradually making each layer smaller than the last. Cut as many layers as it takes to refill the repair to the original surface.

  • Mix the resin with the hardener as directed on the containers. Use the mixing bucket and stir stick to thoroughly mix the resin.

  • Wet the surface of the repair with the resin mixture using the felt roller. Apply the smallest layer to the repair, and apply the resin with the felt roller. Wet the mat until it is the color of the resin with no dry white spots left. Role out the air bubbles using an air roller. Repeat this process for each layer until all layers are applied. Let the fiberglass cure until it is hard and cool to the touch.

  • Sand the fiberglass using fine-grit sandpaper and a palm sander until it is smooth and level with the surrounding surface. The repair should match its original surface.