Boat Paint Part 2

Bottom paint is a thorny issue for every boater because some of the most effective formulas are toxic (it is part of what makes them effective). Again the choice of paint will also be influenced by how you use and store your boat. A wooden boat can require a very different paint than a fiberglass boat. A wooden boat that is in the water year round may require a different paint from a boat that spends half the year in a boat yard or boat shed. A boat that is sailed regularly, or is moored in a strong current, can make use of ablate paints that require regular movement through the water to be effective. This wearing away process helps keep marine growth from attaching to the paint and it also does away with paint build up on the bottom of the boat. Clearly the paint that wears away has to go someplace, it does not just disappear, so one of the costs of ablate paint is environmental. This may not be a big cost if you consider the size of your boat and the size of the ocean, but it is still a cost, and the effect in a crowded marina or anchorage of many boats can be measureable. On the other hand softer bottom paints that have to be removed every so often due to build up have the disadvantage of having to be handled when you apply them and handled when you remove them, and then you need to dispose of the paint chips or combination of old paint and stripper.

The bottom of the boat

There is a range of paints available and choosing which one to use can be confusing. The temptation is to choose the most toxic available to keep the bottom of your boat clean, but the price is much higher for the environment and for those people who are going to have to work with the paint. Finding an effective paint that is the least toxic to the environment and to people seems to me to be the ultimate goal. Bottom paint requires careful handling, either have professionals do this work for you, or if you are going to do the work yourself, err on the side of caution. If you are not sure whether you need to wear a respirator, wear one. If you are not sure what would happen if you get the paint on your skin, wear coveralls and gloves. This stuff can be dangerous and it plays for keeps.

If you do need to strip paint from the bottom of your boat, there are some new alternatives that are safer to work with than the strippers of years past. Since I don’t strip the bottom of our boat, I can’t speak from first hand experience about these products, but I can say that Soy Strip, made by Franmar has an excellent reputation for getting the job done and leaving as little toxic mess as possible. (I have used it to remove Bristol Finish, two-part varnish and it worked well, I have just not tried it on bottom paint.) If you would like more information go to for more information.

In our case the boat spends better than half the year in the boat shed, the hull is cedar planked with white oak garboards and the keel is made of Benghazi with a lead shoe. Although our boat does not dry out much over the winter in her shed with a dirt floor, the bottom paint needs to be flexible enough to move with the boat for what drying does occur. The planking was primed with red-lead primer and over this we use Hydrocoat by Pettit paint Company.

Hydrocoat is a ablate paint, which means that it is designed to wear away slightly over time as the hull passes through the water. This means that there is minimal paint removal that needs to be attended to, but there are always some areas that need attention. I place rubberized, heavy-duty drop cloths in the work area before I start to work on the bottom of the boat and wear a full array of protective clothing, from full-face respirator to spray sock, coveralls and gloves. I use a vacuum system with any sander that I use and I vacuum those drop cloths when I am done working. Any waste chips that are collected go to the HAZMAT collection day at the local transfer station and are clearly marked. Having said all that, Hydrocoat is considered to be more environmentally friendly, and user friendly than a lot of bottom paints. It is water-based for a start (don’t ask me how that works, it just does) and has a lower release of VOCs (Volatile Organic Compounds) than many bottom paints. However, it does contain cuprous oxide and therefore still needs to be handled carefully.

Most bottom paints function by using cuprous oxide as a main ingredient. Some paint manufacturers add something called a biocide. When I was growing up around boat yards the conventional wisdom was that the higher percentage cuprous oxide, the better the bottom paint. However, it is also classified as a hazardous material, and as dangerous to the environment. Further some of the paint formulas use drying agents that are highly evaporative and this combination makes for potentially dangerous fumes while the paint is drying.  At the very least read the Manufactures Safety Data Sheet and follow the recommendation for safe handling.

I have read about a new bottom paint created by a company called E-paint that works on a different principle than using oxides of copper and other heavy metals. The technology has to do with a different type of chemical reaction. “Photo-active technology where visible light in the water column is used to photo-chemically generate hydrogen peroxide around the boat hull by combining water and dissolved oxygen molecules; the hydrogen peroxide deters the settling of hard-type fouling larvae such as barnacles, mussels and oysters.”* However, I have yet to meet anyone with a wooden boat, sailed in salt water, that has used or tested it. If you have tested one of the E-paint products, please leave a comment, and let me know what your experience has been.

*From the E-Paint website:


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One Response to “Boat Paint Part 2”


    excellent run-down on current bottom paint technology. Warmer climates require greater cuprous oxide %. Northern waters can use some of the newer gen paints, but agree good copper content is way to go. Some are using this vinyl additive thanks chuckm

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