Bottom paints are usually one of two types: hard or ablative, with variations whose effectiveness depends on how much time the boat spends in the water, and how often it moves.

Hard bottom paints are typically less expensive than ablative antifouling paints. However, hard paints are effective for a single season, and they build up season after season, eventually requiring costly removal. Ablative paints come in single-season and multiseason varieties and don’t build up.

Hard bottom paint dries hard, stays that way, and doesn’t wear away gradually like an ablative paint. It works constantly while the boat is in the water, regardless of whether the boat is moving, and stops working once all its copper biocide gradually leaches out. So the coating can still be in great shape, but the biocide is gone and so is the protection. Water can seep in to the unprotected coating and damage the hull. Also, because hard bottom paint doesn’t wear away, it builds up and eventually has to be removed–a costly, labor-intensive endeavor.

Another problem for hard bottom paints is they lose their copper faster–and their effectiveness–if the boat is kept out of the water more than 60 days after applying bottom paint. For this reason, hard bottom paint is typically used on boats that remain in the water for extended periods. It’s also great for boats operated at faster speeds, like racing boats, because it can be burnished to increase hull smoothness and speed, unlike ablative bottom paints.

Ablative bottom paint wears away gradually as water flows under the hull, either from use or tidal movements. As the paint wears away, it exposes a fresh burst of biocide to keep biofoulers from attaching to the surface. There are ablatives for multiple season use, and others that are effective for a single season. The single-season ablative paints are typically less expensive than the multiple season ablatives.

For most ablative paints to work effectively, motion is required, so this paint is best if you use your boat fairly often–at least once a week. A hull painted with a single-season ablative antifouling paint can be pulled and left out of the water up to two weeks, but will require a light scuffing with a Scotch-Brite pad to reactivate the antifouling properties directly prior to launching.

A hull coated with a multi-season ablative can be pulled and left out of the water up to two weeks, without scuffing to reactivate the antifouling. However, after two weeks, scuffing is required directly before launching.

Self-polishing, copolymer ablative bottom paint also wears away gradually to expose fresh layers of biocide. However, it’s effective whether or not the boat is moving because it uses a self-polishing, controlled-release, copper copolymer formula. Some copolymer ablatives can last multiple seasons, requiring only a light scuffing to reactivate the antifouling in the spring, directly before launching.

Hybrid copolymer ablative bottom paint has all the self-polishing, controlled-release biocide benefits of a copolymer ablative. The difference is that it can also be burnished–like a hard bottom paint–for smoothness and speed, unlike other ablative bottom paints. And there’s less buildup to remove next season, as with hard bottom paints.

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