Features October 2006 Issue

Fending Off the Funk

Hard or soft? Colored or white? Lots of copper or none? The challenge of picking a bottom paint these days is enough to leave even the most experienced maintenance guru staring blankly at the shelves in the paint aisle. Our aim with this update—PS’s 12-month review of bottom paints—is to make the world of antifoulants a bit easier to navigate.

The first step in choosing an anti-fouling paint is deciding between a hard or soft coating. Our Best Choice and Budget Buy paints in each of these categories are indicated on the tables listed in "Also With This Article."  Where you boat can greatly effect antifouling performance, so these tables also signal top performers in each location. If other factors like easy cleanup, eco-friendliness, or color are important priorities, then you’ll also want to check the table and article on specialty paints listed in "Also With This Article" Looking for a protective coating for your sail-drive? See “Outdrive Paints” in "Also With This Article, Metal Antifouling Paints." And for the latest on anti-slime paints, see "Also With This Article."

PS is testing 52 different bottom paints from seven manufacturers. Three of these paint makers are household names: Pettit, Interlux, and Sea Hawk. They account for 38 of the paints tested. Blue Water Marine Paints, which hit the market in 2003, has become a major player also, with eight entries in this 12-month follow-up report. Blue Water now provides paints to Boater’s World that are sold under the Sea Bowld label.

Since half of the paints tested claim to remain effective for multiple seasons without recoating, we decided to pull the panels at six-month intervals for three years. This extended test was also prompted by feedback from paint manufacturers regarding performance of their paints with anti-slime additives. In our six-month report (March 2006 issue), we saw little difference in performance—the amount of slime or soft growth—between the paints with additives and those without. Manufacturers’ explanation: The anti-slime paints’ effectiveness becomes more evident with time.

A large group of paints fall under the umbrella of “soft” paints. Within this group there are a few subcategories that deserve explanation. First, there are true “soft” paints that slough off over time. Pettit Premium SSA and Interlux Tarr & Wonson Cop-per Paint are good examples. These rosin-based paints are good choices for boats that are used often, but not scrubbed in the water. They must be repainted after the boat is pulled for extended storage.

You asked for it: Freshwater boaters have urged us to test bottom paints in fresh water. A set of painted panels took the plunge in Fairport Harbor, Ohio, on Lake Erie in July. We’ll pull them in November and report our findings in the February 2007 issue.

The second group of “soft” coatings consists of copolymer paints, which release their biocide (copper) at a controlled, constant rate. (Interlux Micron Optima and Pettit Horizons and Ultima SR are copolymer paints). They are effective even after long periods of storage, and are good for heavy-growth areas. Some of these copolymer paints, such as Interlux Micron 66, are resin-based and also are referred to as “polishing paints.” They’re good for multiple seasons and are recommended for heavy-growth areas. “They have the advantage of becoming smoother over time, yielding less drag,” according to Interlux’s Jim Seidel.

With any soft coating, applying a different color “signal coat” for the first coat will help you know when it’s time to repaint.Hard paints are modified-epoxy coatings that leach biocide at a steady rate upon contact with the water. The paint itself remains, leaving a hard coating of the original thickness at season’s end. So after several seasons of painting, you’ll have a thick layer-cake of bottom paint. These paints lose effectiveness when the boat is stored for long periods.

Hard paints are generally one-season paints, and are good for boats that aren’t hauled often because they can be scrubbed frequently in the water.

We tested thin-film paints such as VC 17M Extra and Pettit SR-21, which are best for low-fouling or freshwater areas. They use a slick finish (Teflon is used in VC 17M Extra) to prevent growth from adhering.

Bottom paints are now available in white and bright colors: Interlux (Trilux 33), Pettit (Vivid), Blue Water (Kolor), and Sea Hawk (Mission Bay). Keep in mind that white paints tend to make growth more visible.

The specific copper contents appear in the charts on pages 24-25, where we also list whether the paints are recommended for one or multiple seasons. Three paints do not use copper—all are from E Paint.

Newcomers include Kolor from Blue Water, Interlux’s Super Ablative with Slime Fighter, Super KL with Slime Fighter, Fiberglass Bottomkote with Irgarol, and Fiberglass Bottom-kote ACT with Irgarol. Pettit has one new paint in this test, SR-21, a paint for fresh- and low-salt water. For the first time, we also tested Sea Hawk’s Tropikote Biocide Plus and Cukote Biocide Plus.

We’ve submerged a fresh batch of panels with 2006 paints in the Florida Keys, Connecticut (Long Is-land Sound), and for the first time in several years, Lake Erie, in Ohio.

Following the manufacturer’s instructions, we apply the paints to new polyester/fiberglass panels. Each panel is prepped for painting and identified by a series of holes drilled in a simple binary code. One set of panels is in a saltwater canal in the Florida Keys, the other is tied to the docks at a boatyard in eastern Long Island Sound, Conn.

The panels, which took the plunge in July 2005, were rated in early January for the March report and pulled in early July for this report.

Panels are rated after being sluiced with a bucket of salt water. For scorekeeping this round, we eliminated plus and minus ratings (Good , Good-, etc.) used in the March report; these were just splitting hairs. Otherwise, scoring remains the same as before: Paints with any hard growth rate Poor; panels that are virtually clean rate Excellent. Fair and Good ratings are based on slime coverage relative to the rest of the field.

A few samples (mostly soft paints in Connecticut) scored slightly better after one year than they did after six months, even when we took into account the scorekeeping change. This might be attributed to a boost in biocide after being sluiced, or any number of wintertime environmental factors (lower temperature, increased water movement, etc.) that might have improved these paints’ performance relative to others.

• Only one paint—Interlux Bot-tomkote Aqua—scored Excellent in both Florida and Connecticut.

• Five paints notched a combina-tion of Good and Excellent in the two test locales: West Marine Bot-tomshield, Interlux Tarr & Wonson Copper Paint, Interlux VC Offshore, Pettit Hydrocoat, and Sea Hawk Monterey.

• Three of these top six paints are water-based coatings: Pettit Hydrocoat, Interlux Bottomkote Aqua, and Sea Hawk Monterey.

• Four are under $100 per gallon: Interlux Bottomkote Aqua ($70), West Marine Bottomshield ($70), Tarr & Wonson Copper Paint ($60), and Pettit Hydrocoat ($95).

• Three are one-season hard paints (Interlux Fiberglass Bottom-kote Aqua, Interlux VC Offshore, and West Marine Bottomshield); two are multi-season copolymer paints (Sea Hawk Monterey and Pettit Hy-drocoat); and one is a one-season soft paint (Tarr & Wonson Copper Paint).

• None of the best performers are eco-friendly. All use copper.

• None of the white paints made the top six this time around.

Not only is Interlux Bottomkote Aqua the best-performing paint so far, it’s the second least expensive paint in the field. And it’s a water-based paint, a huge plus, in our opinion. If you need a one-season hard paint, Bottomkote Aqua is a no-brainer. It is not sold through West Marine or other discount marine stores.



E PAINT CO., 800/258-5998

FLEXDEL CORP., 888/353-9335


KOP-COAT (PETTIT), 800/221-4466


SEALIFE CORP., 310/338-9757

WEST MARINE, 800/262-8464

BOATER’S WORLD, 800/826-2628

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