All of us, no matter how "clean" we are or try to be, have a complicated and extensive bacterial and viral flora on our skins at all times, even when we are just out of the shower. Most of these organisms are harmless most of the time, but, occasionally, we will all carry, particularly on our hands, viral and bacterial pathogens (disease-causing organisms).
This is a matter of particular concern to piano teachers, since every client of the studio, both children and adults, will use the same piano(s). What can the teacher do to prevent or, at least, reduce, transmission of viruses and bacteria by contact with the piano keys, thereby protecting both the teacher's health and that of the students? Let's discuss that issue with particular emphasis on what things the teacher can do to reduce transmission of pathogens, without running the risk of damaging the keys of the piano.
Please note that this article should not be construed as offering medical advice. If you need medically-related information, seek help from a medical professional.
Unless you can understand the nature, chemical reactivity and purpose of the label ingredients for a cleaning product, avoid using it on your piano.
Hygienic Practices in the Teaching Studio
Of course, probably the best thing you can do to maintain a hygienic environment in your studio is to encourage sick students and parents of sick students to stay home and make up lessons when they are feeling better. But many students will come to your studio seemingly perfectly healthy, but still carrying pathogens on their hands, through contact at school, work or just about any other public location. Most medical professionals will tell you that frequent hand washing is the best way to avoid transmitting illness-causing organisms. This is good advice for all of us. I'm aware of a number of teachers who insist that each student wash their hands after they arrive at your studio, but before they start their lessons. Doing this has the added advantage of helping to keep your piano clean. But what can you do in addition to this to protect yourself and your students?
There are several waterless disinfectants that one simply puts on one's hands and rubs in, without the need for washing, per se. Purell® is one example of such a product. According to the Purell web site, the active ingredient is ethyl alcohol (62% by volume) (also known as grain alcohol, but denatured to make it non-drinkable). The site claims that Purell kills "99.99% of germs that may cause illness." Note that it doesn't mention any capability for killing viruses. So, a product like Purell may be a good partial solution if you don't have facilities for washing readily available. It's a way to go for studios that don't have, or don't want to provide, routine access to washing facilities. Note that, because Purell and similar products have so much alcohol in their formulations, you don't want to get it on your piano keys, although that shouldn't be a problem if it is used as intended.
Cleaning and Disinfection of Your Piano Keys
There are many disinfectants commercially available, approved for many different uses. Unfortunately, most of them are not safe for your piano or piano keys in the long run. A piano is just too big an investment to run the risk of damaging it by poorly chosen cleaning/disinfecting methods. So, just what is safe for the piano?
The key tops on a piano are comprised of either ivory, or synthetic polymers, like melamine, ABS (acrylonitrile-butadiene-styrene) or SAN (styrene-acrylonitrile), among others. Ivory is a mixture of various protein (mostly keratin- the elephant version of the protein that makes up our finger and toenails) and non-protein (calcium salts, among others) components. It has very different chemistry than the synthetic polymers. Thus, one can't necessarily expect that a cleaner/disinfectant that will work for synthetic polymer key tops will be suitable for ivory ones.
Here is a part of what Yamaha says about general keyboard cleaning: "Keep the keyboard clean: The keyboard should be wiped periodically with a soft, dry cloth. Never use cleaners containing alcohol, as the keys will become cracked. If the keyboard is very dirty, wipe it with a cloth dipped in a solution of soap and water and wrung out well. The same cloth should not be used for cleaning the surface of the piano, however. A good habit to cultivate is never to play the piano with dirty hands." Steinway gives a similar set of keyboard cleaning instructions.
Given these instructions to use only the mildest of cleaning methods on the keyboard, we are very limited in what they can safely do to promote hygiene. One technique is to simply wipe down the keys with a damp (not wet) cloth after each student. This will not kill viruses and germs but will remove them physically. It's far less likely to damage the keys than disinfectants, but probably less effective.
Perhaps because they are unaware of the potential for damaging the key materials, many people wipe their piano keyboards with disinfectants of various sorts, although, even with those, it's not always certain how effective they are against cold and flu viruses. Because both ivory (a natural polymer) and synthetic polymer key surfaces can be degraded by harsh chemicals like those used in some disinfectants, the choice of a disinfectant for the keyboard can be a tricky one. Bleach wiping of any sort can discolor the keys in a matter of weeks and should be avoided. Many commercially available disinfectants often include organic disinfectants (Tricloban®, hexachlorophene, phenols, ethanol, etc.) as active ingredients, which can dissolve in the polymer (synthetic or natural) making up the key surfaces, swelling and, ultimately, cracking them. They also can catalyze photooxidation (a degradative pathway in which light and oxygen in the air act together to damage the key material), which can discolor as well as crack the polymer of the key surface.
Unless you understand the nature, chemical reactivity and purpose of the label ingredients for the product you are considering to use, avoid using it on your piano - not because it is necessarily a "bad" product, but because you need to be able to assess if the particular product you have is "safe" for the piano. While the chance of an organic disinfectant hurting the keys in the short term is small, in the long term the situation changes. With the hundreds of wipings necessary if you use wipes on your piano regularly and especially if the wiped keys are also exposed to light, many common disinfectants are very likely to discolor and, ultimately, crack the keys.
Given these complications, are there any true disinfectants that can be used on a piano keyboard reasonably safely?
I have looked into the Clorox Disinfectant Wipes that come pre-moistened in a container. There is a claim on the Clorox Disinfecting Wipes web site that a university study shows that such wipes "kill 99.9 percent of viruses that cause cold and flu, as well as bacteria commonly found in kitchens and bathrooms." The active ingredients in these (and a similar product from Proctor & Gamble) are 0.14% "ALKYL (60%C14, 30%C16, 5%C12, 5%C18) DIMETHYLBENZYL AMMONIUM CHLORIDE" and "ALKYL (68%C12, 32%C14) DIMETHYLETHYLBENZYL AMMONIUM CHLORIDE," according to a filing with the California Department of Pesticide Regulation. These compounds are organic-substituted quaternary ammonium chlorides ("quats" in the trade) which have long been known to have bactericidal activity. The "fat-like" organic parts of these molecules turn them into pretty good surfactants, which is the basis of their bactericidal activity. Based on some statements on the Clorox wipes web site, the surface treated with the wipe should be allowed to sit wet for four minutes prior to use.
That said, these wipes look pretty innocuous for the piano keys, assuming that the inactive ingredients are mostly water, but one should still be careful not to allow residues to build up on the keys, even though such residues provide some residual germ-killing activity. I don't believe that much harm could be done to the keys by leaving the the residues on for minutes or, even, hours. Only after building up over periods of days or weeks might they become a problem. That view is also consistent with what Yamaha said about using "soap and water" to clean the keyboard, followed with a damp cloth wipe. Since "soap" often contains the same or similar chemicals for their surfactant (chemist shorthand for "surface active agent") qualities, the two situations should be pretty analogous.
Lysol® brand disinfectants are well-known on the U.S. consumer market, There are numerous Lysol products with very different formulations, some of which are probably safe for the piano. The aerosol can version probably should not be used on piano keys, because it contains alcohol and phenol derivatives that would not be good for the key tops. Lysol trigger spray should be safe for the piano. However, don't spray it directly on the keys. Spray it onto a clean soft cloth and use that to wipe the keys.
Suggestions for Cleaning/Disinfecting
Here's what to do to clean synthetic polymer (modern) piano keys:
routine cleaning: lightly dampened soft cloth with water only; for obvious dirt: a pinch of washing detergent (but NOT one with bleach of any sort in the formulation) dissolved in a cup of water and applied with a soft, lint-free cloth, then wiped with pure water;
for quick disinfection: Clorox Disinfecting Wipes or the corresponding Proctor & Gamble product, followed by a wipe with a damp lint-free soft cloth. Because of their softness, ability to retain particulate matter and washability, a "microfiber" cloth is an excellent choice for the soft cleaning cloth.
For those of us with vintage pianos having ivory key tops:
do not use Tide or any similar washing detergent to clean ivory. Tide and other detergents contain an enzyme or enzymes to aid cleaning of certain kinds of soils. These enzymes will very slowly degrade ivory, since it is comprised, in part, of protein. Avoid putting enzymes like those in washing detergents on ivory.
For ivory keys, a dilute water solution of the simplest soap, followed by wiping with a damp cloth is the safest approach to cleaning. The Clorox wipes are also probably safe for ivory, so long as it is wiped with a damp cloth after the wipe to remove residues.
Be careful of the finish
Whatever method or products you use to clean or disinfect your piano keyboard, be careful not to get the cleaning product on the finish of the piano cabinet. While polyurethane-based "mirror" piano finishes are tough and resistant to damage, most will not tolerate alcohol, for example. Lacquer-based "satin" finishes are even more subject to damage by cleaning agents. This may be the best reason to spray the cleaner on a cloth and then wipe the keys, since you are much less likely to get large amounts of liquid cleaner on the finish.
Maintaining your piano in as hygienic a state as possible, while protecting its value, is an achievable goal. It's just a matter of following manufacturer's instructions for cleaning and knowing a little about which types of cleaning and disinfecting products are safe for the piano and which ones should be kept away from it.