How to Apply Gelcoat to Fiberglass

By Jay Kurz

Gel coat is a fiberglass resin that is pigmented with color. Gel coat also can have additives that protect from UV rays for outdoor applications. It is very thick and is sprayed using a gel coat spray gun. Because it is resin, gel coat needs a catalyst to become hard. The gel coat gun generally mixes this internally while spraying. Gel coat acts both as paint and a protective layer over the fiberglass.

Things You'll Need

  • Respirator
  • Palm sander
  • Fine grit sandpaper
  • Coarse grit sandpaper
  • Rags
  • Acetone
  • Gel coat
  • Gel coat spray gun
  • Methyl ethyl ketone peroxide (hardener)
  • Boat wax

Step 1

Wearing a respirator, sand the entire area being gel coated using a palm sander and a coarse sandpaper. Every crack and crevice should be scuffed thoroughly. After the surface is sanded with coarse sandpaper, go over the entire surface again, using a fine grit sandpaper. The surface should be smooth and free of inconsistencies.

Step 2

Clean the entire surface using a clean rag and acetone. Remove any grease or dust from the surface. Grease can cause the gel coat to bond incorrectly and form bubbles.

Step 3

Fill the gel coat gun with the correct gel coat and hardener. Mix the gel coat thoroughly with an electric drill and a mixing attachment.

Step 4

Spray the first coat of gel coat in a heavy mist. Apply evenly and consistently for the best results. Let the first coat begin to cure and when it's tacky start to apply the second coat. The second coat should solidly cover the surface. Let cure until the gel coat is hard and cool to the touch.

Step 5

Apply two coats of boat wax. Using a rag, buff the wax until you achieve a shiny finish. The wax will act as a protective layer for the gel coat.

References & Resources