Humidity and Pianos

Relative Humidity
Where to Place the Piano
Temperature
Humidifiers and Climate Control Systems

Relative humidity is a measurement, expressed as a percentage, of the amount of water vapor in the air compared to the maximum amount the air could possibly hold at a given temperature. The relative humidity of the outdoor air depends on the nature of the air mass—that is, how moist or dry it is—and on the temperature, because the ability of the air to hold moisture increases with increasing temperature. So if we take a "parcel" of air with a certain amount of moisture in it and we heat it up, the relative humidity will decrease, because the amount of moisture in the air will have decreased in comparison to the amount the air is now capable of holding. Alternatively, if we cool that air, again without adding or subtracting the moisture, the relative humidity will increase, because the capacity of the air to hold moisture will have diminished.

The relative humidity of the outdoor air can be high or low from day to day, regardless of the season. The reason such a fuss is made about low winter humidity is that in climates that have cold winters, the indoor relative humidity is artificially lowered by heating the air with a furnace system without supplying any additional moisture. If, for example, the outdoor temperature is 32 degrees Fahrenheit and the outdoor humidity is 100 percent (an extreme example), by the time the air is heated to 68 degrees indoors, the indoor relative humidity will have dropped (theoretically) to only 28 percent (the actual amount may be a little higher due to human respiration, plants, and other factors).

A continuous exchange of moisture goes on between the air and the wooden piano parts and other porous objects around the house, as the moisture level attempts to reach a state of equilibrium. Since the air is usually a much greater reservoir of moisture than the objects, it tends to dictate the terms of this interchange. When the relative humidity is low, the air sucks up moisture from the piano, causing the pitch to fall, tuning pins to loosen, and parts to rattle (not to mention causing plants to wither, furniture joints to loosen, skin to crack, and throats to get sore).

Piano manufacturers suggest that the ideal humidity level for pianos is about 40 to 50 percent, whereas studies show that for people 50 to 60 percent is best. Actually, as far as pianos are concerned, the particular humidity level is not nearly as important as the change in humidity through the seasons. In most cases, a piano can be adjusted to exist quite well at any reasonable level of humidity as long as it doesn't change much. But when, as happens in most of North America, the indoor humidity goes from very high to very low and back again, year after year, the alternate the alternate expansion and contraction has the net effect of shrinking, cracking, and warping even wood that has been well-seasoned prior to manufacturing. One of the most important parts of good piano maintenance is keeping the humidity as constant as possible.

There are several ways you can protect your piano from extremes and fluctuations of humidity. The most important of these is putting the piano in the right place. NEVER put a piano near or against a working radiator, next to or over a hot-air vent, or under a ceiling vent. If you can't observe this one simple rule, there's no point to even buying a piano. You'll be throwing your money away. A concert pianist who is a customer of mine insisted, over my objections, on situating her $15,000 grand over a large heating vent in her living room. "It doesn't look good any place else," she said. Her piano is now almost un-tunable. Priorities, please!

Some tuners advise their customers not to place a piano near a window or a door because of possible drafts, or against an outside wall that may get cold. This is undoubtedly good advice, but following it may severely restrict your ability to have a piano at all. Use your judgment. My experience is that these factors are often not too significant unless the conditions are extreme. If in doubt, and an inside wall is not available, move your piano six inches away from any outside wall to provide an insulating air space, or try putting a sheet of styrofoam insulation behind the piano. Remember, too, not to place your piano in an usually damp place, such as a damp basement.

Direct sunlight on a piano should be diffused with curtains or venetian blinds. Besides damaging the finish of a piano, sunlight can wreak havoc on the tuning. I remember the time I was called by a grand piano owner who claimed his piano seemed to go out of tune at certain times of the day and back in tune at other times. "Sure", I thought skeptically, but agreed to check it out. Not finding anything obviously wrong, I proceeded to tune the piano. Halfway through the tuning, I discovered, to my dismay that the piano was already going out of tune. Then I noticed that while I had been tuning, the sun had shifted its position in the sky and was not shining directly on the soundboard. I quickly got up and closed the blinds. After five minutes, to my relief and amazement, the piano was back in almost perfect tune.

Another way you can keep the humidity up in the wintertime is to keep the temperature at moderate level. Temperature alone does not affect a piano very much unless extreme, but it decidedly affects relative humidity. A temperature difference of just 5 degrees can make the difference between a house that is hazardously dry and one that is moderate and comfortable. Some of the best-preserved pianos I have seen have been in rooms that were poorly or directly heated. Some of the worst have been in houses heated over 70 degrees. Some piano manufacturers state that the ideal temperature for a piano is 72 to 75 degrees. In my opinion, this is ridiculous. Not only would this be a waste of expensive energy resources, but it can be nearly impossible to keep an adequate humidity level when a house is heated to such temperatures in the wintertime. Studies have shown that the best temperature for physically active people is around 64 degrees, although there is, of course, a certain amount of variation from one person to another (for instance, people who are elderly or ill usually need a much higher temperature to avoid hypothermia). Obviously you need to strike a balance between your health and comfort needs and the requirements of your piano. Fortunately, this balance is usually not hard to find if you are willing to be flexible and wear a sweater indoors from time to time.

Many people are starting to recognize the importance of an adequate humidity level to health and possessions, including their piano. Households in increasing numbers are artificially raising the humidity during the dry months by using humidifiers. These come in three kinds: a central humidifier directly connected to your forced hot-air heating system (if you have this kind of system), a portable unit that can humidify one or several rooms, and a miniature climate control system installed right in your piano.

If you do heat with forced hot air, connecting a central humidifier is by far the best route. A heating and cooling contractor can install one for $400 - $500. This may cost more than the smaller portable models, but it will take care of the entire house with no additional noise or clutter of extra appliances. Central humidifiers are usually designed to refill themselves with water automatically, but you must clean them often to remove mineral deposits, especially in hard water areas, and to prevent the growth of bacteria.

If you heat by other means than forced hot air, you should consider buying a portable humidifier, usually priced from $100 - $200. These, however, require a lot of maintenance. Like the central kind, they must be cleaned often (weekly, or at least monthly) to avoid the growth and spread of air-borne disease. They must also be filled with water quite often (on the average, daily), the frequency depending on the capacity and output of the humidifier, the temperature of the house, and how well the house is insulated. If you go away for a few days and the humidifier runs out of water, the house could get dry and the piano could go out of tune. Also, these appliances tend to make a lot of noise, something to which a musician is likely to be sensitive. Last, when the temperature is very low outside, indoor humidity must also be kept low—often lower than is acceptable for your piano—to prevent water vapor from condensing on windows and other cold surfaces. In fact, too much humidification can result in moisture seeping into the wall, and, over time, causing structural damage to the house. If you would like to avoid this risk, would be bothered by the motor noise of a console humidifier, want to avoid the nuisance of frequent cleaning and filling, go away for long periods of time, live in an area that is too damp all the time, or just want to give extra special attention to protecting your piano, the best route is to have a climate control system installed right inside your piano (see figure on the right). These systems can be ordered and installed by your piano technician. The system consists of a humidifier (a tank of water with a heating element and fabric wicks), a dehumidifier (a long heating element that raises the temperature and thus lowers the relative humidity), a humidistat (sense the humidity level and turns on and off the humidifier and dehumidifier as needed), a low-water warning light mounted under the keybed, and an easy-fill tube so you can refill the humidifier without having to open up the piano. In a vertical piano, the system is installed right inside the lower panel, near the pedals. Optionally available are components that provide protection at the back of the piano, too. In a grand, it fits under the soundboard. The cost for the system and installation is about $300 to $400 in a vertical and $400 to $500 in a grand.

The advantages of this system are that it makes no noise at all, requires filling (extremely easy) only every one to four weeks, depending on conditions, and needs cleaning and changing of the humidifier wicks only once a year, which your technician can do. Since the system covers only a small area, it can control the humidity in that area very closely. The drawback is that it can't reach the entire piano, only the inside of the vertical (unless optional components are installed) and the underneath of the grand. In both cases, it will help stabilitze the tuning, and in the vertical it will protect the action as well, but in a very dry room, it may not provide the kind of total protection that the room humidifier can. I highly recommend these systems for both vertical and grand pianos, but sometimes suggest that they be supplemented by room humidifier, especially for grands, if the piano owner doesn't mind the inconvenience.

To purchase a humidifier or simply get more information please call us at 1-800-241-0001 or use our contact form.

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