How to Repair Gelcoat Crazing

Written by jay kurz | 13/05/2017
How to Repair Gelcoat Crazing
(Hemera Technologies/ Images)

Gelcoat crazing occurs when the layer of gelcoat becomes cracked or fractured but the fibreglass underneath remains undamaged. Gelcoat is a thick fibreglass paint used as a protective coating over fibreglass as well as for cosmetic reasons. Crazing must be repaired as soon as possible to avoid any damage to the fibreglass the gelcoat is protecting. The damaged gelcoat must be sanded away and replaced with fresh gelcoat to seal the surface from water and other contaminants.

Sand directly on the crazing until the damaged gelcoat is completely removed. Use a palm sander with 80-grit sandpaper to remove the damaged gelcoat and then switch to 300-grit to smooth the area out.

Wipe the area clean, using a rag damp with acetone to remove any dust or residue that may affect the gelcoat's bond.

Pour the amount of gelcoat you need for the repair into a small bucket. Add 1 to 2 per cent catalyst to the gelcoat and mix it in with a paint stirrer.

Apply the gelcoat to the affected area, using a 4-inch felt roller. Let the first coat begin to get tacky and apply the second coat. Continue applying coats of gelcoat until the area you sanded is built back up to the surrounding gelcoat surface. Let the gelcoat harden for two to three hours.

Apply a thick coat of boat wax to the repair and let it dry. Buff out the repaired area, using an electric buffer.


Always wear a respirator or at least a dust mask when working with fibreglass.

Tips and warnings

  • Always wear a respirator or at least a dust mask when working with fibreglass.

Things you need

  • Palm sander
  • 80-grit sandpaper
  • 300-grit sandpaper
  • Rags
  • Acetone
  • Small bucket
  • Catalyst
  • Paint stirrer
  • Felt roller
  • Boat wax
  • Electric buffer

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