How to use a fibreglass cloth and resin car repair kit

Updated February 21, 2017

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

Sand the surface of the repair using coarse-grit sandpaper. Scuff the entire area so it is dull and smooth to the touch. The fibreglass 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 fibreglass 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 colour 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 fibreglass cure until it is hard and cool to the touch.

Sand the fibreglass 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.

Things You'll Need

  • Coarse-grit sandpaper
  • Rags
  • Acetone
  • Fibreglass resin
  • Hardener
  • Mixing bucket
  • Stir stick
  • Felt roller
  • Air roller
  • Fine-grit sandpaper
  • Palm sander
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About the Author

Jason Kurz has been a published writer for and for less than a year now. Kurz attended Kent State University of Ohio for Computer Aided Design.