The marble countertops in a reader’s kitchen. (Reader photo)

Q: The marble countertops in our kitchen were new when we bought our house two years ago. Now they are completely covered in what look like water marks. Maybe the stone wasn’t properly sealed or finished to begin with? We use a marble-safe cleaner, so I don’t think that’s the problem. What can I do to fix the problem and make the marble look shiny and new again?

Washington

A: The “water marks” could easily be etching left by lemon juice, vinegar and other acids. Marble (like limestone and travertine) contains calcium carbonate, which dissolves in acid. A sealer helps prevent stains but does not stop acid etching, said Hunter Dasch, vice president of Rose Restoration (800-413-9893; www.roserestoration.com), a company that restores marble surfaces throughout the Washington area and Florida. “That’s a common misconception,” he said.

When a polished marble countertop has only a few etch marks, it’s often possible to restore the shine for $10 $15 by rubbing with a soft cloth and a paste made of water and a marble polishing powder, such as Miracle Sealants’ Water Ring & Etch Remover or M3 Technologies’ Majestic Etch Remover. However, it can take several long minutes of polishing to treat a single etch mark.

When countertops throughout a kitchen are covered with etch marks, or if the etches are so deep that they remain even if you try to polish them out, it’s time for professional help. Rose Restorations would use power equipment with diamond abrasives to remove the etch marks, then polish the stone and seal it. “Diamond abrasives are to stone what sandpaper is to wood,” Dasch said. The crew would start with 50-grit, then switch to progressively finer abrasives, with grit sizes of 100, 200, 400 and 800. Around 400 to 800, the stone starts reflecting light. After 800, the crew uses a polishing powder, which results in a shiny surface. Then the stone is resealed. To treat a typical marble-topped kitchen island often takes one person five to eight hours, at $75 an hour. A typical kitchen needs a two-person crew ($120) and eight to 10 hours.

It’s possible to add a coating that keeps any spilled acids from touching the stone, but a clear topcoat changes the look of the stone. Most homeowners opt to skip that, Dasch said. Instead, they pay to have the countertops refinished every three to eight years, depending on usage and how picky they are about wanting a gloss finish.

You can also opt, as part of the refinishing, to switch from polished to honed marble. The refinishing crew would just stop at 800 grit. Because the stone wouldn’t be as shiny, any new etch marks wouldn’t be as noticeable. However, if they occurred, you couldn’t rub them out with an etch remover without risking creating a shiny spot. Dasch said a better touchup option would be to lightly sand with 800-grit wet/dry sandpaper.

Of course, a third option is to just let the etching happen. Over time, the surface will become more evenly dull and you will stop noticing it so much.

Some years ago we updated our front entry. Now the bricks are showing black residue. How do we clean the bricks without harming them?

Fairfax

The black residue is almost certainly mildew. It doesn’t hurt brick, but if you don’t like the look you can remove it with household bleach or a moss-and-mildew cleaner from a hardware store or home center.

For uniform cleaning, the bricks should be damp. So tackle the cleaning job on a drizzly day or hose down the bricks before you start. If you’re using a specialty cleaner, follow the label directions.

If you’re using bleach, the least expensive option, mix 1 cup of bleach to 1 gallon of water. Wearing old clothes, rubber boots and rubber gloves, use a synthetic scrub brush or broom to slop the solution onto the bricks. Scrub enough to distribute the solution. Wait a few minutes, then hose off the bricks.

If you had a large area to clean — not your situation, from what shows in the picture you sent — you could use a power washer fitted with a rotating surface cleaner. This attachment is sold along with power washers. Tool rental companies can also supply both the machine and the attachment.

Have a problem in your home? Send questions to localliving@washpost.com . Put “How To” in the subject line, tell us where you live and try to include a photo.