Run your hand along an older fibreglass hull and it may come away white or tinted with the colour of the boat. That chalky film is oxidized gelcoat, and it is the most common problem we see on boats in Ontario.
What Gelcoat Is
Gelcoat is the hard, coloured outer layer of a fibreglass boat. It protects the fibreglass underneath and gives the boat its colour and shine. It is also slightly porous, which means it absorbs stains and is broken down by ultraviolet light over time.
Why It Oxidizes
Sun is the main cause. UV light breaks down the resin at the surface of the gelcoat, leaving a rough, chalky layer that scatters light instead of reflecting it. Heat, lake water, bird droppings and harsh cleaners speed it up. Coloured gelcoats such as red, blue, green and black show it fastest, but white hulls go dull and yellow too.
How Bad Is It?
Light: The hull looks a little flat and hazy but nothing comes off on your hand. Usually a single polishing step and protection will bring it back.
Moderate: A clear chalky residue comes off on a finger or cloth and the colour looks faded. This needs compounding and polishing.
Heavy: The surface is rough, very chalky and the colour is badly washed out. This may need more than one compounding pass, and sometimes wet sanding first.
Why Wax Alone Doesn't Fix It
Wax fills and covers. On an oxidized hull it will darken the colour for a while, but the damaged layer is still there and the dullness comes back within weeks. Oxidation has to be removed, not covered.
How It's Removed
The hull is washed and decontaminated first. Then a machine polisher with a cutting pad and compound removes the oxidized layer, followed by a finer polish to restore clarity and gloss. A test section shows which pad and compound combination works before the whole hull is done. Striping, decals and logos are worked around carefully.
Protect It Afterwards
Freshly polished gelcoat is bare, and it will start to oxidize again if it is left unprotected. A wax, sealant or ceramic coating keeps the gloss. A ceramic coating lasts much longer than wax and makes the hull easier to clean, which is why many owners add it right after polishing.
Keep It From Coming Back
Wash the boat regularly with a marine soap, rinse off bird droppings quickly, use a cover or store it out of direct sun, and top up the protection as recommended. That will keep the gelcoat looking good for many seasons.