Bottom Paint, Antifouling for Wooden Boats.

Choosing a bottom paint for your boat used to be simple, the more toxic the better.

Fortunately there is now a greater awareness of the impact on the environment that man made pollutants are having.

And while the effect that the paint on your small boat may have might seem insignificant, add it to the accumulated effect of all the paint from the other small boats and it becomes quite a problem.

The trouble is that while the biocides in the bottom paint deter the organism which foul the boat they also have a detrimental effect other marine life and the very waters which we use our boats to enjoy.

Before buying an antifouling paint do check the latest regulations for your sailing area.

Copper is being banned by many port authorities and even scrubbing off is being legislated against in some areas.

To antifoul or not?

A wooden boat that remains in the water all year is going to need antifoul bottom paint.

However, one which is regularly kept ashore won't need the same kind of protection.

Most fouling organisms survive in specific environments, salt water organisms will die off in fresh water or in the air, so a boat which regularly moves from one to the other may not need much if anything in the way of protection.

And if you do antifoul, the choice of paint will also be influenced by how and where you keep and use your boat.

The amount of fouling can vary depending on temperature, salinity, water quality and temperature as well as the amount of sunlight, the and flow of the water and other pollution levels.

Because most fouling occurs along the waterline where it is encouraged by sunlight it is regarded as good practice to apply an extra coat or two here and on the rudder, however these are areas which are easy to scrub clean with out the need to haul out.

And any water pollution on the surface can affect the efficiency of the antifoul.

So, if you keep your boat in the water, check with your neighbours, the marina and other boat users in your area to get an idea of the local problems, and try to find the most effective but least toxic solution.

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Types of Bottom Paint

The wide range of available antifouling paints can be confusing.

Basically there are three main types;

  • Erodible or self polishing
  • Soft, traditional
  • And hard or Ablative.

While the active ingredients in all three tend to be similar it is the how they are put together that determines the type.
Erodible or self polishing;

In this type the active ingredients are suspended in a resin which will once in the water begin to dissolve in a controlled way.

This allows fresh layers of the active biocides to be exposed on the surface.

Traditional or Soft

These tend to be cheaper than the more modern self polishing.

They use a much more simple resin binder to hold the biocides, so while they offer good cheap protection, they are not as efficient over the season.

The soft type need to be applied shortly before launching, so check the instructions on the tin.

One disadvantage of the softer bottom paints is that they have to be removed every so often due to build up.

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Hard or ablative

As the name suggests these bottom paints are more resistant to abrasion.

As with the others the active ingredients are held within a resin, however this is less soluble.

Ablatives use what is known as contact leaching which needs regular movement through the water to be effective.

These paints are designed for high speed power boats, boats kept on a mud berth and racing yachts.

Some other types;

Teflon based bottom paint is also available, has been developed for racing yachts, however it is not particularly effective as an antifouling if used without a biocide.

One part modified epoxy paints tend to contain the highest biocide levels of any antifouling paint.

They are durable, abrasion resistant, however they are difficult to remove and do gradually lose their effectiveness when out of water.

Water-based antifoulings
encapsulate the biocides in a water-soluble polymer resin.

They don't lose their effectiveness when the boat is hauled and re-launched, and are reasonably easy to recoat.

While they use very little or no solvent and thus contain very few volatile organic compounds, they do still contain toxins.

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The active ingredient in most bottom paints is methylene chloride, which is a carcinogen.

Read and obey the safety instructions on the tin for your own sake as well as that of the environment.

If you are not sure whether you need to wear safety gear, wear it.

When stripping off old bottom paint place a heavy duty tarp or cloth below the hull before starting, and wear protective clothing and use a vacuum system with any sander, vacuum up debris when done.

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