How to Buff a Fiberglass Gelcoat

Buffing the gelcoat finish removes oxidation from fiberglass boats.

Gelcoat is a polyester resin and coloring pigment applied to the inside of molds during the fabrication of boats, recreational vehicles and other fiberglass products. During the curing process, gelcoat resin hardens to become the glossy, reflective top layer of the fiberglass. Maintaining a good coat of wax is the best way to preserve gelcoat. However, with time and exposure to the elements, all gelcoat eventually oxidizes. Early signs of oxidation are cloudiness and dullness in spots. Eventually, the entire surface will become nonreflective and the gelcoat may show evidence of microscopic pitting. Gelcoat in this stage of oxidation can be restored with a sanding and buffing procedure including the use of rubbing compound.

Things You'll Need

• Fiberglass degreaser/dewaxer
• Wet/dry sandpaper in grits from 1000 to 3000
• Automotive style electric buffer
• Wool buffing pads
• Tack cloths or terrycloth towels
• Spray-on marine fiberglass polish
• Marine paste wax

Instructions

1. Wash down the entire surface of the fiberglass with a commercially available fiberglass degreaser/dewaxer.

2. Wet sand the surface with progressively finer sandpaper beginning with 1000 grit and ending with 3000 grit until the surface is uniformly flat with no shiny areas.

3. Wash the sanding residue off the surface and allow to dry.

4. Divide the surface into 2-foot squares. Apply rubbing compound to one square at a time and rub it into the surface briskly in circular motions. Allow the rubbing compound to dry to a haze.

5. Buff the rubbing compound off the square using a variable-speed automotive body style buffer with soft-edged wool buffing pads. Set the buffer to run at 2,000 rpm or less to minimize swirl marks or scratches. Keep the buffer moving to avoid "burning" the gelcoat finish. Remove the compounding dust from the surface with a tack cloth or clean terrycloth towels.

6. Compound, buff and dust each square until the entire surface is compounded.

7. Apply a liquid or spray-on marine polish to the surface. Allow the polish to dry to a haze and buff with a soft-edged wool polishing pad on the buffer.

8. Apply marine paste wax to the surface. Allow the wax to dry to a haze and buff with a soft-edged wool polishing pad on the buffer.

References

• Boat US: Restoring The Shine To Fiberglass
• 3M Corporation: Achieving Production Gelcoat Finish PDF