How can I remove hard water stains from stone countertops?

Washington Post

14-02-2025

Q: I need to replace my kitchen faucet. I have hard water from a well, and there are white-ish stains at the base of the faucet where the faucet meets the granite countertop. Is there a way to clean this area to remove the stain? And, is there a way to clean it quickly, as I'll have a plumber waiting to complete his work?
A: A new single-edge razor blade is probably the magic wand you need. There are chemical ways to remove mineral deposits and the soap scum that's often mixed in with them, especially where the water is considered 'hard' because it is high in minerals, such as calcium and magnesium. But unless the deposits are very thin, chemicals aren't likely to produce a quick cure. Plus, you have the ideal situation for simply scraping off most of the ugliness: You're dealing with a hard stone and you won't need to worry about nicking the faucet because it will be out of the way.
'Once the faucet is out, use a razor blade,' said Cameron DeMille, a technical support specialist for MB Stone Care, a company in Wilson, North Carolina, that makes stone cleaners, stain removers and other products for stone surfaces.
He cautioned, though, that this advice holds only for granite, quartzite and quartz surfaces, with quartzite meaning the natural stone and quartz referring to the manufactured product that consists of ground quartz minerals mixed with resins and often pigment. A razor blade would remove mineral deposits from marble, travertine and limestone, but these stones are softer and you might wind up scuffing the countertop, DeMille said. It would be safer to call in a pro to refinish those surfaces with diamond abrasives.
Mineral deposits form when water repeatedly dries on a surface, leaving behind minerals it picked up when traveling through soil or rock before getting to a home's water supply. The deposits are most likely to form where there is hard water, which also keeps soap from doing its job and leads to deposits of soap scum. At first, the deposits often look like water spots, but eventually they become more noticeable, especially in places like the bases of faucets, where water drips off hands. Regularly cleaning the area and wiping the surface dry after each use can prevent the deposits, but once they start forming, you can't just wipe them away.
The deposits are alkaline, so acidic cleaners, such as CLR Calcium, Lime and Rust Remover ($6.28 for 28 ounces at Home Depot), eat away at them effectively. CLR is labeled safe to use on plastic, ceramic tile, glass, stainless steel, faucet and shower fixtures, shower doors, fiberglass, toilet bowls and sinks, although there is a warning that the cleaner might etch older sinks, tubs and tiles. But the manufacturer says explicitly not to use CLR on natural stone, including granite. Similar warnings appear on many other acidic cleaners.
There are other products that remove mineral deposits and soap scum from natural stone, but they are best used when the deposits are just beginning to form or when most of the deposit has been scraped away. Those include MB Stone Care's MB-3 Soap and Mineral Deposit Remover ($19.97 a quart from the company's website). Designed for use on concrete, granite, marble, limestone, travertine, quartzite, serpentine and terrazzo, it is a strong alkali, with a pH of 13, comparable to bleach or oven cleaner. So, just as with the strongly acidic mineral deposit removers, you need to follow directions carefully, including protecting your eyes and skin when using it. And you shouldn't expect instant results.
'It's pretty slow,' DeMille said. 'Faucets get crusty.' That's why he recommends using a razor blade to remove most of the gunk on a countertop or other surface made of hard stone, then following up with the Soap and Mineral Deposit Remover to clean off the remnants.
To avoid scratching the countertops, keep the blade at a low angle to the stone. Moisten the surface with water for lubrication. You don't need to worry about scraping off the sealer on your countertop, DeMille said, because the sealer is almost certainly a penetrating type, which sinks into pores in the stone and winds up just below the stone's surface.
Some soap scum and mineral deposit removers labeled for use on natural stone are acidic. Rock Doctor Spot and Ring Remover ($13.99 for 14 ounces on Amazon) has a pH of 1.7, about 10 times as acidic as vinegar. The directions say to rub it on with a damp sponge, soft cloth or paper towel and to repeat the procedure with more pressure if the deposits persist. The product contains finely ground quartz, which acts as a superfine abrasive to wear away deposits as the acid is chemically weakening them, said Melinda Dames, who handles customer service for Rock Doctor, a company in Lenexa, Kansas, that makes a range of stone care and kitchen cleaning products. About half the customer reviews on Amazon rated the product five stars, but about one-third gave it just one or two stars, and some of them complained that it dulled the surface. Dames said the company has tested the product extensively and seen no damage. It's common for customer feedback to run the gamut, from good to bad, she said.
So a word to the wise: Test whatever product you plan to use in an inconspicuous place before you use it in a high-visibility area such as by the sink. You might not be able to test its effectiveness at breaking down deposits, but you can evaluate whether it makes the surface dull or pitted. Do the test well before the plumber arrives so you have time to find and try an alternative if you need to.
Have a problem in your home? Send questions to [e-mail]. Put 'How To' in the subject line, tell us where you live and try to include a photo.