Gelcoat Geek-Out

Mirror, mirror on the wall, how do I make my boat shine brightest of them all?

We don’t want our boats to merely look good. We want them to look stunning! Rather than just shine, we want them to emit a radiant, heartwarming gleam. The largest surface area on most boats is gelcoat, and there are countless products on the market claiming to give our boats’ outer skin a spectacular shine. Decades ago we used paste wax, then came liquid

wax, polish, and most recently ceramic sprays. But which type of product gives the finest shine? And which lasts the best over time? If you go by the marketing hype or the print on a bottle’s label, they all do.

Methodology

To figure out which type of finish product truly gives a boat’s gelcoat the best appearance when used for a DIY detailing job, we tried three different brands of each on the plain white gunwales of a boat with 10-year-old gelcoat in average condition. To eliminate as many confounding factors as possible, we first cleaned the surface (which had been waxed with paste wax five months prior) with acetone, then gave it a thorough wash with soap and water. Next, we applied the products in 4-inch-wide bands, separated by black lines on the gelcoat using a (hopefully not completely) permanent marker.

Some notes: The brightness of the gelcoat’s gloss was measured using a calibrated glossmeter with +/-1 GU (gloss unit) repeatability at a 60-degree angle. This is the standard measurement used for automotive finishes; we found no identifiable standard for the marine industry. We chose product brands based on popularity because that reflects what we boaters use the most in the real world, however, we should remember that using brands we didn’t test could lead to different results. Results could also vary depending on the condition, age, and/or exposure of an individual boat’s gelcoat. In the case of the spray-on ceramic coats, all were DIY consumer versions, not the professionally applied type (which is a huge distinction). Finally, all products were applied as per the manufacturers’ instructions.

Initial Results

As a baseline, we measured both the unwashed and the washed gelcoat prior to product application. Then we measured the gloss produced by each product in each product group three times and averaged all the results for the group. Here’s what the glossmeter showed us (drum roll, please):

As the numbers make clear, all of these product groups turbocharged the shine-factor as compared to the untreated surface. However, some of the results were surprising. Simply washing the gelcoat caused a huge percentage gain in the gleam, so when your boat-loving heart desires an “eye-motional” quick fix, perhaps the best move is to simply break out the hose and scrub brush. All these product groups were effective at substantially boosting the shine and were separated by a glossmeter difference of less than 10%, so it’s safe to say they all worked. But polish came out on top for the finished shine factor, despite all the hype we hear about ceramics and all the grumbling we hear from wax-loving old-timers.

We also learned a bit about the importance of product choice. The concept of this process was to compare product group types against each other, not individual brands against one another. So we’ve attempted to remain brand-agnostic in this article. But we need to note that the spread in effectiveness between brands was at times dramatic. One of the ceramics earned a very high 19, but the group was dragged down by a poor performing 13, the lowest post-shine glossmeter score we recorded. One liquid wax also lagged at 13. And only one of these products, a polish, managed to score an epic 21.

Time Will Tell

So far, so good. But as we boaters all know, that gorgeous finish only lasts so long. Which type of product would continue to deliver its shine over the long run? To find out, we used the boat as usual for the next month. It sat out in the sun and rain, got a few saltwater dousings, and received washdowns with a scrub brush and boat soap. Then we remeasured each band of treated fiberglass. Here’s what we discovered:

As the glossmeter’s numbers made clear, a month of weathering slightly reshuffled the deck with liquid wax jumping into a tie with polish for the lead, and paste wax finishing with a strong second. The spray-on ceramics lost additional ground. Again, certain products were underperformers and significantly dragged down the totals, while some others overperformed. The same standout polish that scored highest initially dropped only 1 GU, from 21 to 20. And none of the polishes were serious laggards, leading us to believe that boaters in search of the ultimate shine should definitely have polish in their DIY detailing bucket.

All In All …

Truth be told, standing back and gazing with our own eyes, it was tough to see any real visible difference between the treated areas. All boosted the shine factor significantly, and after a month, the difference between the polish, liquid wax, and paste wax was so small as to be undetectable by our eyeballs. There was a barely perceptible difference at the transition point between one of the ceramics and a liquid wax, but it took some serious straining to make it out, and we’re not even sure it is visible in the picture we took.

The difference between the treated zone of gelcoat and the rest of the boat, however, was blatant. In fact, it felt a little funny taking people out on the boat during this monthlong endeavor because guests couldn’t help but notice that there was one strip of shine with a bunch of black lines on the otherwise dingy gunwales. This is a great reminder that applying a midseason treatment is a must if you want your boat to still be shiny come fall, no matter what type of product you opt for.

It’s also a good reminder that if you don’t want to spend a month driving around in a funny-looking, mostly dingy, shiny-in-one-spot, marker-lined boat, you might want to think twice before joining the BoatU.S. editorial team.