How to Sand Fiberglass Resin

Fiberglass resin comes in many variations, each with a specific task.

Fiberglass is a very durable material commonly used for boats.Fiberglass is a very durable material commonly used for boats.
Fiberglass resin is a thick liquid that requires a catalyst in order to harden. After the catalyst, which is methyl ethyl ketone peroxide, is mixed into the resin it will chemically react and cause the resin to heat up and then harden in 20 to 30 minutes. After the fiberglass is completely hardened it can be sanded smooth to prepare it for gel coat.

Put on a pair of rubber gloves and pour the amount of fiberglass resin that you need in a small bucket.

Add one- to two-percent catalyst to the resin and thoroughly mix it in, using a stir stick. When the resin becomes one consistent color the catalyst is completely mixed in.

Apply the resin to the site, using a four-inch felt roller. Let the fiberglass harden for 45 minutes to an hour, or until it is hard and cool to the touch.

Put on a respirator and begin sanding the fiberglass. Sand it with 320-grit sandpaper if the fiberglass is getting gel coat. Otherwise you can use 100-grit.

Things You Will Need

  • Rubber gloves
  • Fiberglass resin
  • Small bucket
  • Catalyst
  • Stir stick
  • 4-inch felt roller
  • Respirator
  • Sandpaper


  • Always wear a respirator when working with fiberglass.
  • Always wear skin protection when working with catalyst to avoid chemical burns.

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.