Caring for a piano in a damp British climate

Why a British piano lives in a difficult climate

There is a particular kind of damp that only really makes sense to those of us who live on these islands. It arrives in October and settles in until April, drifting through sash windows and solid brick walls, hanging in the air of an unused front room. Wood, felt, leather and steel — the four materials a piano is mostly made from — all respond to that moisture, and none of them respond well.

The good news is that a piano is not fragile. It is, however, sensitive. A modest amount of attention to the air around it will keep an instrument playing sweetly for decades, and almost all of that attention costs very little.

What damp air actually does to your piano

The soundboard is a large, thin sheet of spruce under considerable tension, and it behaves like a sponge. When relative humidity climbs, it swells; when it drops, it shrinks. Nothing about that movement is gentle on tuning:

• Swelling raises pitch. A soundboard that has taken on moisture pushes the strings slightly sharper, which is why a piano tuned in a dry February can sound wrong by June.
• The action becomes sluggish. Felt and leather bushes in the action absorb moisture and swell, so keys feel heavy, repetition slows, and notes begin to stick. Damp is the single most common cause of a "slow" keyboard.
• Strings and pins corrode. Rust on plain wire and tuning pins is disfiguring, but worse, it changes the friction at the bearing points and makes tuning less stable and less pleasant to listen to.
• Glue joints and veneers suffer. Prolonged damp softens hide glue, and you may see veneer lifting at the edges of the case or a slight ripple along the lid.
• Mould appears. It usually starts on the underside of the soundboard or on the felt, and it smells exactly as you would expect.

Measuring the air before you worry about it

Buy a digital hygrometer before you buy anything else. They cost about the same as a decent takeaway and they turn guesswork into fact. Place it on the piano, not across the room, and read it at different times of day for a week.

A piano is happiest between roughly 45 and 65 per cent relative humidity, with around 50 per cent being the sweet spot. Below 40 per cent you risk a cracked soundboard and loose tuning pins; above 70 per cent you are in the territory of swelling, sluggishness and rust. In a typical British home, the reading will swing more than you imagine between a wet November morning and a centrally heated January evening.

Practical steps to keep the damp at bay

You do not need a climate-controlled studio. You need a few sensible habits and one modest appliance.

• Use a dehumidifier with a humidistat. Set it to hold the room at about 50 per cent and let it switch itself on and off. A desiccant model works better than a compressor type in a cold room. Empty the tank regularly, or run the drain hose to a sink.
• Keep the room closed while it runs. A dehumidifier fighting an open window is an expensive way to dry the garden.
• Move the piano off external walls. Leave at least 10–15cm of air gap behind an upright, and never push it flush against a solid brick or stone wall. In older houses, that wall will be the dampest surface in the room.
• Avoid the obvious enemies. No radiators directly behind the instrument, no conservatories, no garages, no cellars, no kitchens or bathrooms with their steam. A draughty hallway is kinder than a warm, humid utility room.
• Ventilate when the weather is dry. On a bright, breezy day, a short blast of fresh air does more good than harm. On a wet one, keep the windows shut.
• Close the lid. A closed lid and fallboard slow the exchange of moisture between the room and the action. A breathable cotton cover is useful; a plastic sheet is not, as it traps condensation.
• Consider a heater bar system. Fitted by a technician inside an upright or under a grand, a low-wattage bar controlled by a humidistat gently warms the air around the soundboard. It is not a substitute for a dehumidifier in a genuinely damp room, but it is excellent insurance.

Seasonal habits that make a difference

Think of the year in two halves. From late spring into autumn, the battle is against humidity, and your dehumidifier does most of the work. From late autumn through winter, central heating dries the air dramatically, and you may find the hygrometer dropping into the thirties. That is when a small room humidifier, or simply a bowl of water near a radiator, helps balance things out.

Have the piano tuned twice a year if you play it seriously — typically once in late spring and once in late autumn, after the two big seasonal shifts have settled. Tuning in the middle of a rapid change is money wasted, because the instrument will simply drift again within weeks.

When to call in a technician

Some problems are best not left. If keys are sticking persistently, if you can smell damp when you lift the lid, if you see rust on the strings or white bloom on the felt, or if the tuning has become wildly unstable, book a visit. A technician can regulate the action, treat small areas of corrosion, and advise on whether a heater bar system is worth fitting in your particular room.

Damp is not a crisis, it is a condition — and like most British conditions, it is manageable with a little foresight, a hygrometer and a dehumidifier that quietly hums away in the corner. Look after the air, and the piano will look after the music.