Q: Ten years ago, a bathroom vendor installed three cultured-marble vanities in our unit but said nothing about applying a product to keep the surface looking fresh. This year, I noticed that all of the vanities have very fine scratches. Our project manager said that the vendor has gone out of business and that no one else is interested in trying to restore the vanities. I found online advice suggesting using "automotive paint buffing compound and a handheld buffer." There seem to be a lot of liquid granite/marble products on the market, but nothing exactly called automotive paint buffing compound. Can you provide details, and is this something an able 80-year-old can do?

Gaithersburg, Md.

A: Yes, even an 80-year-old should be able to make scratched cultured-marble countertops look better.

Cultured marble is a mixture of polyester resin, catalyst, fillers and pigments that are molded in forms coated with a clear gel coat. When the mixture cures and is flipped out of the mold, the gel coat becomes the top surface. It’s what gives cultured-marble countertops their smooth, glossy look.

To keep cultured marble looking like new, manufacturers recommend sticking with cleaning products that don’t contain abrasives, because those would scratch the surface. But over time, scratches can still appear, either because someone used an inappropriate cleaner or just from ordinary use.

If the scratches are very fine, it might be sufficient to coat the surface with a product such as Gel-Gloss Kitchen & Bath Polish ($7.95 for an eight-ounce bottle from Amazon). You could also use a similar product, Original Gel Gloss RV One Step Polish and Protector, which is sold by Home Depot in 16-ounce bottles for $7.17. A customer service representative for TR Industries, the manufacturer of both products, said they are identical except that the product with RV in the name contains ultraviolet inhibitors to protect against sun damage. Both products, she said, would be fine to use on countertops. The products’ safety sheets are identical and list only two ingredients: water (80 to 90 percent) and very fine quartz particles (10 to 20 percent).

For use on a countertop, TR Industries recommends applying the liquid with a clean microfiber cloth and using another clean microfiber cloth to buff it out. But the instructions warn that that treatment might not be enough for countertops like yours: “For the older, harder to clean surfaces we recommend using an orbital buffer if the manual process is not effective. Multiple applications are recommended for better surface protection, and a superior shine.” But if too much Gel-Gloss is added at a time, the surface could wind up looking foggy. You would then need to remove the Gel-Gloss with soap and water, as well as mineral spirits.

Given that, it might be wiser to use Gel-Gloss as the last step and to concentrate first on removing the scratches. That is what’s recommended by Luke Haas, who is president of Elite Marble Company (608-297-2175; elitemarble.com) in Montello, Wis., and a board member of trade group International Cast Polymer Association.

His company offers a repair kit for its customers that has the same materials his crew uses to take out scratches on countertops in factories. Depending on how severe the scratches are, they first sand with 600- to 800-grit sandpaper. They then switch to an automotive buffing compound and buff out scratches left by the sandpaper.

“It’s more effective if you use a buffing machine, but it can be done by hand,” Haas said. “But if you’re doing it by hand, you’d have to go to higher and higher grit” of sandpaper, to 1,000 and then 1,200. (With sandpaper, the higher the grit number, the finer the abrasive.)

For the sandpaper, you could use wet-dry sandpaper or sponges such as the 3M Sanding Sponges sold in a set on Amazon for $9.79. You would need only the two finest-grit sponges: ultrafine (equivalent to 800 to 1,000 grit) and microfine (1,200 to 1,500 grit).

For the buffing compound, Haas’s company uses Aqua Blue 100 Fast-Cut Compound, which is sold on Amazon in gallon containers for $44.95. “But that’s because we use so much of it,” a spokeswoman said. “You could use any auto buffing compound.”

One example is Turtle Wax T-241A Polishing Compound & Scratch Remover ($5.49 on Amazon for a 10.5-ounce container). Any auto-parts store or the auto-parts aisle of a hardware store or home center would have equivalent products. Just be aware that products labeled as “rubbing compound” are more aggressive than those called “polishing compound.” The rubbing compound might substitute for the sandpaper, but whatever you use to get the existing scratches out, you need to follow it with a polishing compound.

If you decide to invest in a buffing machine, avoid models with 10-inch-diameter pads; those need two hands to maneuver and are oversize for use on a vanity. Instead, look for a lightweight, one-hand model that’s easy to handle, such as the Ryobi 0.5-amp corded six-inch orbital buffer/polisher, $34.97 at Home Depot.

Removing the faucets before you sand and buff would allow you to refinish the countertop evenly, but that would add plumbing steps. Rather than tackle that, Haas suggests leaving the faucets in place but wrapping the base of the metal with painter’s tape in case you accidentally get too close with the sandpaper or buffer.

As a final step, he recommends coating the countertop with Gel-Gloss. “It’s a fantastic product,” he said, and it will give your countertops a like-new gloss.

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