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How to remove paint from wood without damaging the finish

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Q: I had painters in my house a few weeks ago and just noticed paint left on the sideboard in my dining room. This is beautiful cherry furniture and is part of a custom set made for me by John Landis. How do I get it off without damaging the furniture?

A: Because you know who made your piece, a quick phone call to John Landis Cabinetworks in New Jersey (215- 520-9071; jlcabinet.com) was all it took to identify the type of finish: a Sherwin-Williams catalyzed varnish. John Landis, who designs all the pieces his company makes but now has a crew that works on the fabrication and finishing, said he also adds paste wax as extra protection over the varnish on surfaces that will get a lot of wear, such as the top and surrounding edge on your sideboard.

Paint doesn’t stick well to catalyzed varnish and especially not to wax, so there’s a good chance you might be able to scrape the paint off with a fingernail, he said. That would be especially likely had you noticed the paint earlier. Water-based paint, which accounts for most paint used these days, dries within a few hours, but it takes several weeks to cure and become tenacious enough to withstand being washed or scrubbed.

Christopher Brazie, whose LinkedIn profile identifies him as “Technical Services Specialist, (Old Paint Fart)” for the Industrial Wood Coatings Division at Sherwin-Williams, also said scraping off the paint with a fingernail is the best thing to try first. There’s no risk of damaging the finish or altering its sheen, or of smearing paint residue across the surface, which could happen if you softened the drip with solvent.

But because the paint is probably cured by now, it might not be able to be scraped off. Brazie said that, when he’s asked about removing cured paint spatters from clear wood finishes, one of his first questions is whether the spatters are overspray — a bunch of tiny spots that landed when paint was being sprayed — or blobs of paint that dripped or were smeared from a brush. Spatters dry quickly, because they’re so small, he said. The best way to remove them is to buff them with a wool pad, like what car buffs use to shine vehicles. Mounting the pad to a drill or buffer works best, because the speed knocks off the paint, but it’s also possible to hold it and buff it yourself, he said.

Drips and smears from a brush take longer to dry, which means they are easier to scrape or wipe off at first. But if drips and smears cure, you might need to dab on a solvent to soften the paint, so you can scrape or wipe it away without damaging the finish.

Luckily for you, using a solvent is probably less risky with conversion varnish than with other finishes. Conversion varnish, which is made by many companies, is a two-part finish that has to be mixed in a precise ratio before it’s sprayed on. Traditional lacquer finishes, which some furniture and cabinetmakers use, are single-component finishes. Conversion varnish goes on thicker, meaning the applicator has to apply fewer coats. The coats also are more scratch-resistant and, in most cases, more resistant to spills of food or household chemicals. Brazie said conversion varnish is the best clear finish for wooden furniture. “It’s the clearest clear coat, and the toughest and most durable.”

Sherwin-Williams makes three types: Sher-Wood water white conversion varnish; a similarly named product that has “Kemvar LF” in its name; and Sher-Wood F3 Kemvar varnish. The LF is code for “low formaldehyde.” The F3 version is formaldehyde-free.

All are sold only as industrial finishes (not ones you’d typically find at a home center). According to the products’ technical data sheets, 22 chemicals — including foods such as lemon juice and butter, as well as solvents such as household ammonia, 50 percent ethyl alcohol and turpentine — have no effect on the basic conversion varnish, which accounts for most sales, or on the low-formaldehyde version. But the formaldehyde-free conversion varnish isn’t so durable. It’s listed as resistant to only 10 liquids — the same as for Sher-Wood catalyzed lacquer (Precat). But even that list does include alcohol — specifically 100-proof alcohol, which includes whiskey.

That all three conversion varnishes and the catalyzed lacquer list alcohol as something unlikely to damage the finish is significant: Alcohol is usually the safest way to soften and dissolve cured water-based paint, Brazie said. But the proportion of alcohol to water shouldn’t be more than 50 percent, so he suggested diluting denatured alcohol with one-fourth to half as much water. If you’re using 70 percent rubbing alcohol, mix 7 teaspoons with at least 3 teaspoons of water.

Don’t pour the diluted alcohol mixture on the wood. Instead, moisten a corner of a soft cloth and dab the solution on with that. Wait a minute or two, and test whether the paint is soft. If not, wait a bit longer. Alcohol evaporates quickly, so reapply if necessary to keep the paint damp. When the paint softens, scrape it off.

If you didn’t have the advantage of knowing what kind of finish is on your furniture, you could still start by trying to scrape off the paint with a fingernail. That’s always safe. But before using a solvent, even one labeled for use on furniture, you’d be wise to ensure it won’t affect the finish. Test in a place that isn’t very visible, such as the inside of a leg. Apply a little solvent, wait a couple of minutes, then rub with a cloth to see whether any finish comes off or whether the surface dulls. Alcohol dissolves shellac, for example.

Have a problem in your home? Send questions to [email protected]. Put “How To” in the subject line, tell us where you live and try to include a photo.

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