Cleaning piano keys with toothpaste: Why plain white paste can help, and which types to avoid

Old pianos come with stories and usually stained keys to match. You know the problem if you’ve lifted the dust cover off a family piano only to see the white keys looking more mustard than ivory. The trick circulating online is to dab a little toothpaste on a damp cotton bud, work it gently into each key, and then wipe the surface dry immediately. It sounds too simple to work, but the basic chemistry behind toothpaste offers a clue as to why it helps.

A 2023 study published in the peer-reviewed journal Dentistry Journal looked at how the concentration of abrasive particles in toothpaste affects its ability to wear away surface material, the same basic mechanism at work whenever toothpaste is used to lift stains off any hard surface, teeth included.

Why a little toothpaste really works


Plain white toothpaste isn't magic. It's mildly gritty. Most formulas contain fine particles of calcium carbonate or silica, ingredients dentists use to remove stains from tooth enamel. The Dentistry Journal researchers tested the effect of different concentrations of abrasive particles on surface wear. Using laser-scan profilometry to measure microscopic scratch patterns, the researchers found that a toothpaste's abrasiveness increased as the concentration of abrasive particles, such as hydrated silica, went up. That is why a gentle rub with toothpaste can remove the yellow film from piano keys without needing anything stronger.

That’s also why toothpaste works so differently from harsher cleaners. Keys can get too wet for too long with soap and water, and strong chemical cleaners can eat away at the surface. A bit of ordinary toothpaste, rubbed in with a soft cloth or cotton bud, gives just enough gentle scrubbing power to shift built-up grime, without scratching or soaking the keys.

Plastic or ivory? It makes all the difference

It helps to know what your keys are made of before you reach for the tube. Most American piano makers had switched to plastic key tops by the 1970s, but a few manufacturers overseas continued to use ivory into the 1980s. One reason there are so few new pianos with real ivory keys is that international commercial trade in elephant ivory was banned in 1989 under the Convention on International Trade in Endangered Species, according to the US Fish and Wildlife Service.

Plastic keys are pretty low maintenance and can take a light clean with toothpaste without too much fuss. Ivory keys require more care, as ivory is a porous bone-like material that absorbs moisture and stains much more easily than plastic.

There’s a quick way to tell which one you have. Look closely at a white key. Real ivory is made of two thin pieces glued together, so it usually has a very fine straight seam across the surface. The plastic keys are moulded in one piece and won't have this line. If you've inherited an upright from a parent, or purchased one second-hand, as many millennials are doing these days when furnishing a first home, this quick check is worth doing before any cleaning begins.

How to use toothpaste to clean piano keys correctly

Regardless of the material, the process remains gentle and unhurried. Wipe the keys first with a soft, dry cloth to remove any loose dirt. After that, moisten a cotton swab or a piece of fabric with water and apply a drop of plain white toothpaste to it. Apply the mixture to the keys, gently moving in one direction, but not cleaning the whole keyboard at once; only one key after another. Finally, wipe off all the toothpaste with a clean, slightly moistened cloth, making sure no sticky residue is left between the keys, and dry the keys carefully.

Speed is important here. The most damage is done when moisture is left on the keys, particularly ivory keys.

The toothpaste you should avoid

Gel toothpastes, whitening formulas, and anything with added colour or bleaching agents are best avoided altogether on piano keys, especially ivory ones. These products often have stronger whitening ingredients like peroxide-based compounds and dyes not present in regular white toothpaste.

The Canadian Conservation Institute, a government agency that gives recommendations to museums on how to properly take care of ivory and bone objects, warns that these porous materials can be damaged permanently with exposure to the strong chemical and colored contents of the toothpaste. An innocent-looking gel or whitening toothpaste can leave you with an unsightly, irregular stain on your key which will not come off despite wiping or buffing. Use only a plain, basic white paste without gel, colored stripes, and whitening claims.

A quick final word

If you have had a family piano for decades and think the keys are real ivory, try out some toothpaste on the back edge of one key, near the fallboard where it's least visible, before working the whole keyboard. For a well-loved instrument, a slow, careful clean with the right toothpaste will do far more good than a rushed one with the wrong tube.