The test boat's original red hull and blue bottom paint allowed testers to easily judge which stripper performed best.

Soy bean-based stripper beats out other fast-acting products.

To paraphrase from our 2000 paint stripper test: What expletive that we haven’t used before can we possibly mutter to describe the onerous task of stripping bottom paint?  From application of the gelatinous goo to the scraping, wiping, and sanding, it’s simply one of the most – if not the most – tiring, nasty jobs a boat owner faces below the waterline.

Because removing bottom paint is such an odious task, we’ve tried most every method available over the years: scraping, sanding (both wet and dry), sand blasting, soda blasting, and chemical strippers.  None is ideal, and each has its own set of pros and cons.  The concern with early strippers was the toxic nature of the products.  The active ingredient used in many was methylene chloride, a known carcinogen.

The good news is that chemical companies have developed and promoted safer, more environmentally friendly strippers over the last several years.  These “greener” products have significantly gained in popularity (the bulk of strippers in our test allowed soap and water cleanup) and have been the focus of our last two stripper tests.

WHAT WE TESTED

Back To Nature had three strippers in the running: Ready-Strip, Aqua-Strip, and Ultra-Strip.  Other products tested were Sea Hawk Marine Paint Stripper, Interlux Interstrip 299E, Pettit Bio-Blast, Franmar’s Soy Strip, Peel Away Marine Safety, and Peel Away Marine Strip II.  Produced by Dumond Chemicals, Peel Away products were our top picks in our most recent update on paint strippers (Strippers 2000: Peel Away Still Champ, September 2000) as well as previous tests.

The test group included strippers with a variety of dwell times (the time it takes the product to work), ranging from 15 minutes to 24 hours.  In general, the shorter the dwell time, the more powerful the stripper: however, this can be a bit misleading as many with longer recommend dwell times are supposed to be gentler on the gel coat.  Faster-acting strippers (such as Interstrip 299E and Pettit Bio-Blast) remove paint faster, but may present a greater risk of gel-coat damage if manufacturer’s instructions aren’t followed closely.

HOW WE TESTED

Our test boat was a 1978 Union 36 with three to four layers of blue, ablative bottom paint.  (We mention the color here because our test boat’s gel coat below the waterline is red, making the amount of paint removed relatively easy to see.) Testers applied each stripper – following each manufacturer’s instructions to the letter – to 1 foot x 1-foot sections of our test boat’s keel.  Test results are based on the amount of paint removed from each test panel with a putty knife after the products’ maximum recommended dwell time. The percentage of paint removed given in the test results is approximate, but we believe a fair comparison of how each product performed.  Also compared was ease of application, cleanup, price, and performance.  The high temperature on the day of our test was 85 degrees.

READY-STRIP MARINE

One of three strippers by Back to Nature Products that PS tested, Ready-Strip Marine is bulled as an environmentally friendly, biodegradable stripper that won’t damage gel coat (or any surface, according to the instructions), and can remove most types of marine paints, varnishes, urethanes, and bottom paints from fiberglass, wood, aluminum, etc.

Ready-Strip is unique among the strippers tested:  It changes color (from blue to light blue or off-white) to indicate when stripping action is completed, normally four to 24 hours.  An eggshell-like skin formed over the stripper after about four hours (manufacturer states this helps “lock in” the stripper to improve performance), after which the product was dry to the touch, but presumably still eating away at the bottom paint.

We scraped a small area after four hours (the minimum time recommended), and the panel was completely scraped at 24 hours (the maximum recommended time).  Approximately 85 percent of the paint came off at the four-hour mark.  However, performance was not as good after 24 hours (about 70 percent), possibly due to the product’s drying out overnight and some coating re-solidifying.

Bottom Line: Ready-Strip did better after four hours than after 24 hours.  This emphasizes the need to determine dwell time based on a test patch rather than assuming the max time is best.  With 85 percent removal, Ready-Strip is a stripper we’d recommend.

AQUA-STRIP

Advertised as a “technically advanced, safer marine stripper designed to remove multiple layers of marine anti-fouling, topside and other paints, and varnishes in one application,” Back to Nature’s Aqua-Strip can be used on fiberglass, wood, and aluminum.  Like Ready-Strip, Aqua-Strip is paste-like; it’s thick enough to cling well to the vertical test panel, but still goes on smoothly. After the maximum wait time of 24 hours, Aqua-Strip peeled off easily (in sheets almost) and removed approximately 85 percent of the paint.

Bottom Line: Aqua-Strip performed well overall and a bit better than Ready-Strip, although it costs roughly $15 more per gallon.

ULTRA-STRIP

Billed as a fast stripper, Back to Nature’s Ultra-Strip is advertised as being able to remove one layer of paint in as little as 15 minutes and two to four layers in less than four hours.  Although it was a bit on the thin side, Ultra-Strip still clung fairly well to the vertical test panel.

As speed stripping is the primary claim to fame here, we scraped the test panel after 15 minutes.  Ultra-Strip removed roughly 40 percent of the bottom paint the first go around.  However, after a second application and recommended maximum four-hour wait (for three to four layers of paint), we removed close to 85 percent of the paint on the test panel.

Bottom Line: Although Ultra-Strip removes 85 percent of the bottom paint on the test panel; it took two applications and four hours, which really wasn’t any faster than the other quick-acting strippers – like Inter-Strip and Bio-Blast, both of which are also a bit cheaper.

As a side note: We also tested Ultra-Strip on the Union’s transom where the boat name and homeport were painted on roughly 15 years ago and had been re-painted a few times. We could see the paint lifting within a few minutes.  After 15 minutes, we easily scraped off the remainder with a plastic putty knife.  Once the area was cleaned with a soft scrub pad and mild powder cleaner, no paint remained.

SEA HAWK MARINE PAINT STRIPPER

Sea Hawk markets Marine Paint Stripper as a safer marine paint remover that works on antifouling, topside paints, and varnishes and is safe for use on gel-coat, fiberglass, and aluminum and other metals.

The recommended dwell / test times for the Sea Hawk Marine Paint Stripper were 30 minutes, six hours, and 24 hours.  Sixty percent of the bottom paint in a small scraping of our test panel was removed at 30 minutes, with 70 percent removal at both the six – and 24 –hour marks.  The product was still moist at the six-hour point, but was dry at 24 hours.

Bottom Line: Although the test panel wasn’t difficult to scrape at 24 hours, it was easier to remove the bottom paint at six hours. In our test, the additional wait time didn’t improve the stripping action.

INTERLUX INTERSTRIP

Interlux Interstrip 299E is a semi-paste paint remover that incorporates “special sealing agents” that allow the stripper to stay wet longer, increasing its action time.

Although more environmentally friendly from the standpoint that it contains no methylene chloride, Interstrip 299E is nonetheless some pretty strong - and noxious smelling stuff.  It’s also rated as flammable and as being capable of producing explosive vapors when exposed to heat (according to its Material Safety Data Sheet), and while advertised as safe for fiberglass, instructions caution not to leave it on more than eight hours as gel-coat damage may occur.

As claimed, Interstrip was moist and appeared to be still going strong at the maximum two-hour mark.  However, this “increased action” could be both blessing and curse (due to possible gel coat damage), if you’re not careful to thoroughly remove all residues from the area being stripped once completed. (As is the case with many of these strippers.)

Interstrip powered off 60 percent of the bottom paint on our test panel in 30 minutes and 70 percent at the two-hour maximum recommended time.  Some gel coat damage occurred in our test panel by the two-hour mark however, providing the importance of conduction a dwell-time test.

Bottom Line:  Interstrip 299E worked well and was one of the least expensive test products, but, in our opinion, its potent chemical nature makes it less desirable than the others.  Given our experience, this product requires care, particularly on older hulls with tired and likely more porous gel coats.

PETIT BIO-BLAST

Bio-Blast is advertised as a low-odor, biodegradable stripper designed to remove antifouling paint, but it also can remove varnishes, lacquers, and marine enamels from gel coat, wood, ferro-cement, steel, and aluminum.

Rated as safe for the environment and fully biodegradable, Bio-Blast is also labeled as flammable and capable of producing explosive vapors. Bio-Blast removed 70 percent of the paint from our test panel within 30 minutes, and about 80 percent after the maximum recommended wait of two hours.  The product remained moist the entire test period, and no gel coat damage was noted.

Bottom Line: In the fast-acting category of strippers (those that are removed in two hours or less), Bio-Blast had a slight performance edge over Interstrip and caused no gel coat damage.

FRANMAR SOY STRIP

In 2000, we tested Franmar’s Soy Gel stripper, and found it slightly less effective than our two favorites from Peel Away.  This time we were given Soy Strip, which has 10 percent more active ingredient than Soy Gel.  It is not a new product: just one that we missed.  Like Soy Strip, Soy Gel is advertised as a “natural” solution to removing anti-fouling paints, urethanes, and enamels from boat hulls.  It has no odor, and a very low evaporation rate.

While not as thick as some of the other strippers, Soy Strip still had excellent cling and remained moist during the entire six-hour test period.  After just 30 minutes, it removed 90 percent of the paint in a small test scrape, and at the six-hour mark, it removed approximately 95 percent of the bottom paint from the test panel.

Bottom Line: Soy Strip is powerful. It removed move paint faster than any other stripper, even the “fast-acting” ones. Impressed, we tested it a second time and after one hour the section treated wi8th Soy Strip scraped off almost effortlessly.

MARINE SAFETY STRIP

Both Marine Safety Strip and Marine Strip II utilize a laminated paper to cover the stripper once applied; this is intended to reduce the evaporation rate of the stripper.  It’s also supposed to retain the bulk of the stripped paint, making for easier cleanup.

Marine Safety Strip by Peel Away is advertised as an environmentally safe paint remover for fiberglass, wood, and metal boats. According to the manufacturer, it will remove up to 10 layers of bottom paint in one application without harming gel coats. Marine Safety Strip was still moist and came off easily at the maximum recommended dwell time of 24 hours. It removed 45 percent of the bottom paint from our test panel.

Bottom Line: A favorite in previous tests, Marine Safety Strip went on and came off easily and did not harm the gel coat, but its performance was marginal. Surprised, we tested a larger area, with no better results. After testing was complete, we contacted the manufacturer, who suggested that further scrubbing with acetone would have removed any remaining paint. This was not in the instructions provided, so we did not include this step. We did however, hose, scrub, and scrape at the remaining paint as directed with no marked improvement. Though Peel Away didn’t do as well as the others this time, the fact that it has never damaged gel coat in our tests is worth noting.

MARINE STRIP II

Marine Strip II by Peel Away is billed as an alternative to Marine Safety Strip when stripping barrier-coated hulls. It’s supposed to remove multiple layers of bottom paint in one application without hurting the barrier coat. Marine Strip II was completely dry after 24 hours, the max dwell time; however, it still came off easily and removed 55 percent of the bottom paint from our test panel. As with Marine Safety Strip, we confirmed the marginal results with a repeat test.

Bottom Line: Marine Strip II was thicker, harder to apply, and only slightly more effective than Marine Safety Strip. Estimated coverage per gallon of Marine Strip II (20 square feet) is half that of Marine Safety Strip (40 square feet).

CONCLUSION

Franmar’s Soy Strip performed the best overall, removing the most paint the fastest. Aqua-Strip is our second choice, based on performance, and Ready-Strip is our Budget Buy. Of the fast-acting strippers, Bio-Blast performed well and caused no gel coat damage – but be sure to test a small area of the hull first to get the proper dwell time. Our previous experience with Peel Away suggests it works well with some paints. Still, it appears competing products have caught up with this perennial favorite.