What is Gelcoat and How to Restore It

Gelcoat is the outermost surface of a fiberglass boat. It provides the color and glossy shine to a boat while protecting the fiberglass beneath it. Gelcoat doesn’t provide any structural integrity to a boat, and is strictly there for cosmetic and protective purposes. 

What is gelcoat

Because gelcoat is the outer layer of a boat, some may assume it’s applied as the final step in boat manufacture. However, gelcoat is the first material used when manufacturing a fiberglass boat. Gelcoat is sprayed into a mold before the fiberglass and resin layers are built up on top of it. Once the gelcoat and resin-soaked fiberglass have cured, the component is removed from the mold and the gelcoat becomes the exterior surface. The barrier provided by the gelcoat protects the fiberglass structure from harmful UV rays and water damage.

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Gelcoat Deterioration

Gelcoat deteriorates over time due to continuous exposure to UV rays, heat and water that slowly oxidize, penetrate and erode it. When this happens, the gelcoat loses its mirror-like reflective surface and takes on a chalky, faded appearance.

Oxidized gelcoat

The gelcoat will no longer be smooth to the touch, and may develop cracks or blisters where water has begun to penetrate the surface. Gelcoat is also susceptible to scratches and gouges over time that look unsightly and also increase the chances of water penetration.

Regular washing and waxing prevents gelcoat from deteriorating if the boat has been well maintained. Washing removes any contaminants such as oils and chemicals, while boat wax creates an additional layer of protection over the gelcoat to combat sunlight and water. If the gelcoat no longer feels smooth and glass-like when you run your fingers across it, it’s time to apply a fresh coat of wax. Don’t wait for the gelcoat to show signs of fading before waxing it.

What gelcoat is and how to restore it

Restoring Gelcoat

Restoring weathered gelcoat is simple enough, yet time consuming and labor intensive. To restore neglected gelcoat, you need to remove the oxidized layer of gelcoat using rubbing compound, then polish the gelcoat with boat polish, and finally wax the boat with at least two coats of wax. 

Boat gelcoat waxing

Step 1. Wash the boat with soap specially formulated for use on fiberglass. For areas affected by mildew, use a mildew stain remover. Other stains can be removed with fiberglass stain remover and rust stain remover. Thoroughly rinse the boat after washing and allow it to dry.

Step 2. Use rubbing compound to remove the oxidized layer of gelcoat. Apply the compound using a random orbit buffer or an angle grinder with buffing pad attached, being careful not to burn through a single area. Compound the gelcoat to a uniform smooth surface. Any scratches, gouges, blisters or cracking in the gelcoat should be repaired and filled at this point. 

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Step 3. Polish the boat with a marine polish or gelcoat polish. Marine polish is specially made for use on gelcoat and will return the gelcoat’s surface to a mirror-flat finish. 

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Step 4. Wax the boat to provide a protective coat to the gelcoat against UV rays, water and dirt. The more wax you put on your boat, the more protection and the less frequently you’ll have to repeat the process, so apply the wax in several thin coats. For best results, apply and buff the boat wax by hand.

NOTE: If the gelcoat isn’t oxidized, you can skip steps 2 and 3 and just clean away any grease and oil from the gelcoat before applying the wax. To remove oils and grease from gelcoat, wipe the surface with solvent and a clean rag. Turn the rag frequently, and always wear protective gloves and eyewear when using solvents.

Repairing Gelcoat

Scratches and gouges to gelcoat, or blisters and cracking caused by water penetration can be repaired with a gelcoat repair kit. 

Fiberglass gelcoat repair

Instructions vary from kit to kit, but basically you’ll mix gelcoat paste with a hardener, smooth it over the blemishes, allow it to cure and then sand the area until it’s perfectly flat. Once the scratches and gouges are filled and sanded, you’ll continue to compound, polish and wax the gelcoat as described above.



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