Protecting the wooden heart of your instrument from extreme climate shifts.
The soundboard of your piano is a massive, highly resonant sheet of spruce wood that amplifies the vibration of the strings. In a city like Toronto, where we experience brutally dry winters and tropical, humid summers, this wooden heart is under constant assault. When humidity levels rise in the summer, the spruce absorbs moisture and swells like a sponge, pushing upward against the strings and causing the pitch to go sharp. Conversely, when the furnace kicks on in November and the indoor air dries out, the wood shrinks. If the humidity drops too low, the tremendous tension of the strings can cause the soundboard to literally split open, creating devastating cracks that ruin the piano's tone. At Piano Inside, we strongly recommend installing a whole-home humidifier or a dedicated Dampp-Chaser system to maintain a constant 45% relative humidity year-round.
Piano soundboards are typically made of Sitka spruce because of its incredible strength-to-weight ratio and acoustic properties. However, spruce is highly hygroscopic, meaning it constantly seeks equilibrium with the moisture in the surrounding air. When a soundboard absorbs water, its cellular structure expands. Because the edges of the soundboard are firmly glued to the inner rim of the piano, the wood has nowhere to go but up, creating a 'crown' that forces the bridges against the strings.
The real danger occurs during Toronto's dry winters. If indoor humidity drops below 30%, the spruce rapidly loses moisture and shrinks. Because the wood is pinned down at the edges, the shrinking wood literally pulls itself apart, creating long, jagged cracks along the grain. While minor cracks can sometimes be repaired by a technician using wooden shims, severe cracking leads to a loss of the soundboard's 'crown', resulting in a dead, lifeless tone with no sustain or resonance.
Prevention is the only true cure. As master technicians, we advise our clients to keep their piano rooms strictly between 40% and 50% relative humidity. If managing the entire room's climate is difficult, we can install a professional Piano Life Saver System (often called a Dampp-Chaser) directly inside the piano. This system uses a microcomputer to automatically humidify or dehumidify the micro-climate right next to the soundboard, keeping your instrument perfectly safe and stable year-round.