Polishing Gelcoat

 

This is the first step in restoringyour boat's finish. If the gelcoat is thick enough and mechanically sound, if the color is agreeable to you, this can also be the final step. This is also the step most fraught with danger and snake oils. The gelcoat polishing industry is rife with miracle products that are worthless, “professionals” who genuinely have no idea how badly they're damaging their customer's boats, helpful amateurs who have no idea why it's necessary to polish a boat beyond “because it looks nice”, and an almost universal misunderstanding of product usage.

 

Before discussing how to polish a boat, it's necessary to understand why. Obviously it looks nice. Shiny things are attractive. It's the reason we like diamonds, newly minted coins, and chrome fittings. It's the reason pack rats steal from you. It's the reason children stop in the middle of an intersection to pick up a bottle cap or other discarded bits of scrap. Shiny appeals to our aesthetic. Shiny looks like treasure. Shiny looks clean. Shiny is shiny.

 

Shiny is not why we polish boats. Shiny is the lucky byproduct of a safety and maintenance procedure that most of us are unaware is even necessary. A benefit definitely, but not the reason.

 

Oxidation and UV damage.

 

First, oxidation and UV damage are not the same thing and they don't have the same effect on a boat. Generally, we refer to both kinds of damage under the umbrella term “oxidation”, but it's important to know the differences between them. Technically, oxidation is a chemical reaction caused by exposure to oxygen resulting in the loss of electrons in the gelcoat. The result of oxidation is the chalking you see on the palm of your hand when you touch an unprotected boat. Sealing the gelcoat with a wax or polymer protects the boat from oxidation.

 

UV damage breaks down the binders in the resin used in gelcoat and leads to yellowing and an overall weakening of its mechanical structure. Polishing a gelcoat surface reflects UV light away from the boat. The more reflective the surface, the less UV penetration. The duller the finish, the more UV light will be absorbed.

 

While oxidation only affects the surface, UV damage penetrates the full thickness of the gelcoat and can damage the fiberglass beneath it. Oxidation increases the rate of absorption of UV light because it reduces gloss (reflectivity). Conversely, UV exposure also increases the rate of oxidation by lowering the structural density of the gelcoat.

 

This creates a parabolic effect where a degraded finish will continue to degrade at an ever increasing rate. In other words, a polished boat doesn't just look better than a dull boat, a polished boat will deteriorate at a slower rate than an oxidized boat.

This is why we must first polish the boat and then seal the boat.