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Secrets of a Stripper

What’s the best way to remove old finishes without driving yourself crazy?

Eventually all good things come to an end, and that includes varnish. Over time, your once-gleaming brightwork has turned dull and mousy, with yellow patches of loose varnish, and black stains where water has seeped into the wood; maybe there’s even some bare wood showing here and there. In any case, it’s a sad day for you when you’re faced with stripping and refinishing your brightwork. Time either to collect paint remover, scrapers, sandpaper, and other implements of destruction, or limber up your check-signing hand and call in a refinishing pro. Which path is best for you? Read on before you decide.

Tobi Keitmeier of Nautical Details removes the finish from an old sailboat hatch.

Tobi Keitmeier of Nautical Details removes the finish from an old sailboat hatch.

Putting on a new finish is the easy part; getting the old stuff off is hard, says Tobi Keitmeier, a professional refinisher at Nautical Details in Stamford, Connecticut ( Trained as a cabinetmaker in his native Germany, Keitmeier has specialized in yacht work since he first came to the United States in 1992. He’s written his own training manual on refinishing; he gives seminars on the subject; and satisfied clients often fly him hither and yon to maintain their brightwork. When I met with Keitmeier, he had just finished upgrading the brightwork on a new Monte Carlo Yachts MCY 76 in Florida. Now, for something completely different, he was starting the resurrection of a sorely neglected wooden sailboat. “About 80 percent of a job is doing the stripping and prep,” he says. “Applying the new finish is just 20 percent.” 

Keitmeier says the answer to “strip it yourself or hire a pro” comes down to a question of time: How much do you have to spare? The job will probably take longer than you expect. “Stripping and prepping a handrail, say, takes me half a day,” he says. “It might take [a non-pro] much longer.” But if time isn’t an issue—if you’re retired, for instance—then that’s not a problem. Stripping varnish isn’t rocket science, so people with ordinary skills can do the job, but it’s important not to cause more problems than you solve. If you decide to do it yourself, don’t dive into the job without doing some prep up front, Keitmeier advises. 

Refinishing pros use a variety hook scrapers.

Practice, and Be Careful

Practice with your tools and products on scrap wood until you master them, says Keitmeier. One slip with the scraper can take lots of sanding to repair, and if you use Keitmeier’s favorite tool, the heat gun, you need to learn just how much heat to apply to lift the finish without damaging the wood. “If you smell burning wood, it’s too late!” he says. Use low heat first, and angle the stream of heat onto the surface; don’t shoot it at a right angle. Watch for blistering, then swipe the varnish off with a sharp hook scraper. “And always have a place to put the heat gun down so you don’t burn anything.” Keitmeier demonstrated on the sailboat’s hatch slide; the scraper left the wood clean and smooth, almost ready for sealing.

The key to removing varnish like this is not just finesse with the heat gun, but also keeping the scraper sharp at all times. Use a flat file, and use it often: Filing the blade develops a tiny burr on the back side that actually does the scraping. This burr dulls quickly, so every few minutes the expert refinisher will run his file along the back of the scraper blade to remove the old burr, then file on the beveled side to work up a new one. “Do this off the boat, or in a bucket,” advises Keitmeier, “or the metal filings will leave marks—rust spots on gelcoat or black stains in teak decks.” Take pains to keep the cutting edge straight; there’s a tendency to over-sharpen the blade in the middle and make it concave. Using the scraper efficiently takes practice and care, “and you have to be extra careful when getting close to bare wood not to do damage,” says Keitmeier. But once you get the hang of it, a sharp scraper leaves a nice surface; hit that surface with sandpaper and you’re ready for the first coat of sealer.

Using a heatgun to remove old finish requires finesse and the best scraper for the job.

Using a heatgun to remove old finish requires finesse and the best scraper for the job.

The Chemical Solution

The heat gun/scraper tag team is his favorite stripping method, but sometimes even an ardent environmentalist like Keitmeier has to use chemical strippers on stubborn areas. Many strippers are based on methylene chloride, considered by OSHA a potential carcinogen. Be careful: Methylene chloride can damage gelcoat or painted surfaces, will bleach aluminum, and in some cases even affect stainless steel, Keitmeier says. (Don’t even think about getting stripper on your skin or in your eyes: Always wear protective clothing.) Take as much of the work as possible off the boat and strip it ashore. What you can’t remove, mask carefully. Keitmeier uses 3M plastic drop cloths sold with masking tape already attached to protect transoms, hullsides, and other large areas; they make masking less of a one-armed-paper-hanger routine. Smaller, irregular areas can be protected with a paste of soap to repel chemicals, or, at the very least, keep them wet. Keitmeier suggests having a helper standing by with a hose. “But rinse gently so you don’t spatter the remover all over the place. Use a fine spray, not a stream.” The waste from chemical stripping also must be collected and disposed of in accordance with environmental laws.

There are “green” chemical strippers on the market that don’t have methylene chloride and are therefore less hazardous, but they also work more slowly—too slowly for a professional refinisher like Keitmeier, but maybe not for the casual do-it-yourselfer. If you’re going to strip your own varnish, and you want to do it chemically, try one of these less-aggressive removers first. Move on to the hotter stuff only when necessary. Whatever chemical stripper you use, follow the directions carefully: For example, some strippers can be rinsed off with water once you’re finished scraping, while others have to be neutralized with alcohol or another proprietary solvent. Make sure you finish the job correctly.

Watery mildew is at the bottom of this discoloration.

Watery mildew is at the bottom of this discoloration.

Keep It Clean

No matter how you choose to remove your varnish, things go better if you clean up as you go along, and that’s easier if you have a helper, says Keitmeier. If you’re stripping dry, with the heat gun and scraper, one person can strip while the other follows behind with a Shop-Vac to suck up the scrapings before they blow into the water. When using chemicals, the helper should constantly scoop up the waste and stow it in a proper container. This is very important, since the stuff is toxic and corrosive; you don’t want it getting away from you and causing trouble, and you don’t want to step in it and track it all over the place. (Sounds obvious, but we’ve all done it.) He can also stand by with the hose to rinse off errant stripper.

Once the old finish is off, sand out any stains, gouges from scraping errors, and so forth, and remove random patches of varnish still clinging to the wood. When sanding solid wood (not veneer), Keitmeier uses 100 grit or coarser paper to get the job done faster, saving the dainty 220 and finer grits for sanding between coats of finish. If you’re using an electric sander, choose one with dual action (sometimes called random-orbit) so it won’t leave swirl marks. For sanding in close quarters, a corner or detail sander with a triangular pad works great, but you have to buy the correct sanding sheets to match. If you’re sanding by hand, use a sanding block; the marine store has them, right next to the sandpaper.

Now, by way of conclusion, is this a job you really want to do, or would you be better off hiring a pro like Keitmeier and using your leisure hours to enjoy your boat? If you don’t already own most of the tools mentioned above, you might be better off with the pro. Otherwise, maybe you’ll want to give it a shot, especially if you’ve got time on your hands. I know what my answer would be: Life’s too short to strip varnish. But maybe you feel differently. In any case, appraise the project honestly, and write a check if that’s what it’ll take to bring your brightwork back to life. Your boat will thank you.

2018 Boatyard rule

Sandpaper: The Cutting Edge

You’d think choosing sandpaper would be a no-brainer—there’s coarse, medium, and fine, and that’s about it, right? Wrong: There’s aluminum oxide paper, silicon carbide paper, garnet paper, even ceramic paper. There’s paper you use dry, paper you use wet, paper you use on wood, on metal, and on finishes. There’s paper you use … well, you get the idea. Then there are some abrasives that aren’t paper at all. Here’s the least you need to know.

Aluminum oxide (the brown paper) is a good, all-around sandpaper and what most people reach for. It’s particularly good for sanding wood, because the relatively soft aluminum oxide particles fracture as you sand, exposing new, sharp edges that make the paper keep cutting longer. But if you’re sanding something harder than wood—varnish or paint, for instance, or metal—a harder abrasive like silicon carbide (gray or black paper) will last longer. The folks at 3M recommend their silicon carbide paper specifically for varnish stripping. (Some silicon carbide sandpapers can be used wet to reduce clogging; that’s more like polishing than sanding, not what you want when stripping off finish.)

Garnet paper (reddish) is soft and gentle for fine-sanding wood, popular among cabinetmakers but not so good for removing a finish. Ceramic paper is aggressive, and will take off the finish and the underlying wood if you’re not careful. It’s mostly used in belt-sander and other heavy-duty work, not something you want to use on brightwork.

But hey, you don’t have to use paper at all. 3M makes not only a wide variety of sandpapers, but also Scotch-Brite nylon/polyester pads with either silicon carbide or aluminum oxide abrasive, in a variety of “grits.” Many expert refinishers use Scotch-Brite pads in place of sandpaper, especially between coats of finish. The pads can be used wet or dry, and do a heckuva job at scrubbing pots and pans, too!

This article originally appeared in the May 2014 issue of Power & Motoryacht magazine.