One of the best dollar-for-dollar values in boat ownership is the $20 or so it costs for a bottle of wax to keep gelcoat in good shape.
Gelcoat is nothing more than a base of vinyl or polyester resin impregnated with a colorant. Gelcoat lacks the strength of fiberglass-reinforced plastic, but is durable in its mission to add beauty while requiring little more than simple care and attention. The almond hue of the gelcoat may be all that is left of a 35-year-old trawler on the hard at the last-chance boatyard. And gelcoat will always be the first thing you notice about any fiberglass boat.
The key to maintaining the gelcoat is twofold: Wash it regularly with gentle soap and a thorough rinse to remove air and waterborne dirt and grime, and use oil-based waxes to replenish the petroleum components in the substrate. The bit about gentle soap is key: When I worked at a boat manufacturer, one of the many cardinal rules on the production line was never to use acetone to remove any marks or smudges on fresh gelcoat. This solvent removes and draws out oils saturated in the gelcoat.
Activated gelcoat, if it’s been properly applied with spray or a brush at the factory, generally cures to the thickness of a dime. Because gelcoat lacks inherent strength, thick applications are likely to fracture or produce drips. Ideally, the gelcoat will retain flexibility to absorb the weight of walking on it, while ignoring the grit from dirty boat shoes or the thud of dropping tools.
Another gelcoat trait is porosity. This explains why it is likely to develop stains from exposure to the natural elements, such as wet leaves leaching out their color, as well as tannins in the water from popular cruising areas that foster a mustache at the waterline. Engine and generator exhaust, as well as steel wool or fasteners left behind by careless mechanics, can breed rust stains.
There is no shortage of stain-removal products on the marine store shelves, but if you fail to follow directions, they can do more harm than good. Ultimately, the unsung hero in maintaining and protecting gelcoat is a bottle of wax.
Wax is similar to paint: The results you achieve will only be as good as the surface to which it is applied. If the gelcoat is marked with swirls or an abundance of haze and chalky blotches, then the wax will only make conditions worse. For wax to be effective, you have to start with a clean, wax-free surface.
At the start of the season, I use a soapy mix of Dawn dish detergent and a soft bristle brush. I apply the mix two or three times to flush out as much old wax and grime as possible. This is the only time I use Dawn on gelcoat, because its grease-removing additives will strip fresh wax handily.
Then, I inspect the surface for scratches or scuffs. I prefer a polish with a light abrasive base to scour out any imperfections. This task may require a few passes with the polish, but always remember that the softness and thinness of the gelcoat does not leave you much to work with. Sometimes, a very light pass with 800- to 1,000-grit (wet or dry) sandpaper makes more sense. Follow this step with another polish treatment to best seal the gelcoat from future staining.
With a clean substrate, I’m ready for the first coat of wax. I prefer liquid wax applied with a clean cellulose sponge. Always apply it lightly. Avoid spreading too much wax; all you want to do is fill the gelcoat pores with the sealant and buff it off. Multiple thin coats will fare better than one heavy coat, and the thin coats will always be easier to buff out.
After the first coat of wax is buffed out, subsequent coats are easier. If you prefer to use a power buffer, go slowly and keep the pad moving. You do not want to burn the wax into the gelcoat, or you will be left with a host of swirls that are difficult to buff out.
When doing large areas like a hull, tape off sections and stay within those areas before moving on to the next portion. Change sponges regularly to avoid spreading too much wax, and have plenty of clean cotton rags for buffing. Microfiber cloths are also good for buffing, but do not waste your time with cloths saturated with the wax you have already removed.
Despite what the label on the wax container claims, one application a season is rarely sufficient for long-term success. Regular washings help to keep dirt from baking into the finish, and using a neutral soap that does not remove wax is ideal for better protection against the elements.
Some boat soaps contain a light wax for added durability. They might be a good choice if your boat sees long periods without regular care. Just remember that the maintenance meter is always running, even when the boat sits idle.
This article was originally published in the May/June 2024 issue.
