How Humidity Affects Pianos

upright piano action

What pianos are made from

Season and weather transitions are a good time to talk about how humidity changes can affect your piano. Pianos are made from a lot of familiar materials like wood, felt, leather, metal, and plastic with the main parts being made of wood.

Humidity and wood

Wood is hygroscopic meaning it absorbs moisture from the air. As relative humidity increases, wood absorbs more of that moisture, and desorbs, when relative humidity decreases. Water content in wood increasing can cause the wood to swell. On a piano this may take the form of the soundboard crowning more where the bridge is attached causing more tension on the strings and the pitch to therefore rise. The reverse is true as humidity decreases and wood dries and shrinks. The soundboard flattens and results in looser strings and lower pitch. In extreme cases of dryness, wood can form cracks and splits, which may need to be repaired in order for the piano to function or even make the piano unusable.

grand piano soundboard under plate, strings, & bridge

Humidity and strings

Dramatic changes in humidity resulting in strings tightening and loosening create tuning instability, especially if the pitch ventures far from the correct pitch. In these instances, piano technicians often need to perform multiple tunings to coax the strings back to the correct tension and to a state where they can stabilize and handle finer adjustments.

Humidity fluctuations

Most buildings and homes where pianos are kept experience extremes in humidity over the course of a year through the changing seasons. A piano that goes through extreme humidity changes will likely experience effects on the tuning stability, wearing out of parts, or possibly expensive-to-repair damage to the soundboard or other major parts.

Monitoring humidity changes

How do we know what humidity changes the piano is experiencing? The gauge on a building thermostat is not always accurate and often won’t tell you the humidity levels at the piano. One easy and inexpensive way is to purchase a small digital indoor temperature and humidity gauge, which can be purchased for under $20 online or at local hardware stores. Put the gauge in the piano and check it periodically. Some gauges will even monitor readings over hours and days and report the highest and lowest numbers so you can see the range your piano is experiencing. An ideal constant humidity for a piano is around 42%, but consistency is most important.

Managing the effects of humidity

So what can we do about the effects of humidity on our pianos? Regular maintenance in the form of tunings at least once a year, ideally every 6 months, and more often for pianos that are frequently played is important. It keeps strings at the correct tension and prevents the piano from having to undergo extreme adjustments from going long periods without maintenance.

Another option is to have a piano humidifier like Dampp Chaser installed in the piano by a technician. These humidifiers continuously monitor the humidity in the piano and add or remove moisture as needed to keep the environment consistent. Maintenance is minimal and involves keeping it plugged in and checking the water level once a week. Your technician can clean it during your regular tunings. With regular maintenance and consistent humidity, your piano’s condition will be optimal for play and enjoyment.

Sources

2019 Steinway & Sons. (2019, April 10). Caring for Your Steinway Piano. Steinway & Sons. Retrieved April 28, 2022, from https://www.steinway-boutique.com.ph/news/caring-for-your-steinway/

Piano Technicians Guild. (2022). How does humidity level affect my piano's tuning? Piano Care. Retrieved April 28, 2022, from https://www.ptg.org/ptgmain/piano/care/care-faqs