How to remove gummy residue from hardwood floors

Q: The nonskid padding under the area rug in my family room has melted onto the hardwood flooring. I can scrape the material using a blunt plastic scraper, but there is still residue, and scraping is very labor intensive. I have researched solutions but have not found anything. Is there a way to remove this material and the residue?

A: If you search for the words "nonskid pad residue," you will find a variety of suggestions, some of which are easy to rule out, because they make little sense. For example, one site says to "take Klean Strip Denatured Alcohol and spray it all over the affected surface. This odorless mineral spirit is used as a cleaning agent as it helps to break down the stuck padding." The website goes on to suggest waiting 10 minutes, then scraping with a plastic putty knife and mopping to remove the leftover padding.

What's wrong with that? First, denatured alcohol and odorless mineral spirits are different things. Denatured alcohol is ethanol — also known as grain alcohol, because it's made from starch-based crops — mixed with toxic, foul-tasting additives, so people won't drink it and so manufacturers don't have to pay taxes as if it were an alcoholic beverage. Mineral spirits, a more refined version of paint thinner, is a petroleum-based product. "Odorless" on the label means it has been refined even more to strip it of some of the smelliest — and most toxic — ingredients.

Alcohol, denatured or not, and mineral spirits, with or without the most toxic ingredients, are both solvents, but they don't necessarily dissolve the same things. Denatured alcohol can damage some wood finishes. Mineral spirits, though, is probably safe. But even if you were to test and find that both solvents dissolve or at least soften the residue on your floor, you’d discover that the evaporation rate also matters. Alcohol evaporates very quickly, which is why it's used sparingly in some floor cleaners; it helps the floor dry quickly. For removing padding residue, the slow evaporation rate of mineral spirits is an asset; it gives you time to remove the softened goo before it rehardens.

How to clean and care for hardwood floors

The advice to use a plastic putty knife is good, but mopping to remove the final residue is bad advice, if by mopping one means getting out a mop, swishing it in water, then using the mop to slosh the water onto the floor, so you can wash it. Introducing too much water is always a bad idea when cleaning wooden floors, because the moisture can make the boards swell and buckle.

So, what do you use? Many websites recommend WD-40, which is mostly mineral spirits plus a light oil. But Brett Miller, vice president of technical standards, training and certification for the National Wood Flooring Association, said in an email that WD-40 may damage some floor finishes. Plain mineral spirits would be a better option, he said.

Test the solvent in a small, out-of-the-way area, such as in a closet, to make sure it doesn't affect the floor finish. Then test a small area where the rug pad was to ensure it removes or at least softens the residue enough for you to scrape it off. Miller warned that you might discover that the residue won't come off completely, even with a solvent.

"Many of the lesser-expensive rug pads are coated with adhesives that are intended to enhance the grip," he wrote. "This can damage any wood floor finish. Many carpet rug pads contain chemicals such as polyvinyl chloride (PVC) or phthalates, which can leach into and bond to the floor finish over time." Some pads even discolor the wood itself, he said. When that happens, the only remedy is to sand and refinish the floor.

If you confirm that the solvent is appropriate, tackle a bigger area, but not so big that you can't easily reach across it. Wear chemical-resistant gloves, ensure there's good ventilation and make sure no open flames are nearby. If you’re using mineral spirits, pour some onto a cloth pad, then wipe across the floor; don't pour it in a puddle. For WD-40, use the same procedure or spray it on. Wait for the residue to soften, maybe five to 10 minutes, then wipe it up with a terry cloth or other rough-textured rag. Refold or rotate the cloth after each pass, so you don't smear the gunk over a wider area. On stubborn areas, use a plastic spatula. Once you have removed all visible residue, make a final pass with a little more solvent and a clean cloth.

Finally, remove the oily residue left behind from the mineral spirits or WD-40. Mix one capful of a clear hand dishwashing detergent, such as Dawn, with about two cups of lukewarm water. Dip a clean cloth into that, and wring it out so it's damp, then wipe down an area. Repeat, but with clear water and a clean cloth, then buff dry with yet another clean cloth. Then clean the next area. By working in sections, you can get the floor dry as quickly as possible. Refold and rotate the cloths often, or switch to fresh ones.

To prevent this problem from happening again, shop for a nonskid pad that's labeled as safe to use on hardwood floors.

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