Care & Practice

Humidity, Temperature and Instrument Care

Most damage to instruments comes from slow, ordinary causes: swings in moisture, heat, tension and handling, which are easier to prevent than to repair.

Musical instruments are assemblies of wood, metal, skin, cane and glue that respond to their surroundings. This article sets out general care principles by family: wooden bodies and humidity, brass and corrosion, strings under tension, membranes and reeds. It also covers storage, transport, and the signs that mean a qualified repairer or conservator should be consulted.

Why climate is the first problem

Most of what goes wrong with an instrument happens slowly and without drama. Wood, skin, cane, leather and felt all take up moisture from damp air and release it into dry air, and they swell and shrink as they do. Metal parts respond differently, but they suffer from damp too. The Canadian Conservation Institute notes that musical instruments are often very sensitive to humidity fluctuations and to high humidity, and its general guidance on relative humidity describes cycling moisture as a source of mechanical stress that accumulates over many repetitions.

Two ideas follow from this. First, stability counts for more than any single target value: an instrument that lives at a moderate, steady humidity generally fares better than one that swings between a dry heated room and a damp cellar. Second, change should be gradual. A case carried from a cold car into a warm room is best left closed for a while so that the instrument can adjust before it is opened and played.

Wooden bodies: swelling, shrinking and splitting

Wood shrinks and swells mainly across the grain rather than along it, so a plate or a body that is glued from several pieces is always under slight internal strain. In very dry air the strain can exceed the wood’s strength. Typical results are cracks along the grain, seams that open, bridges that lift, and fingerboards that shrink away from their glue. Very humid air brings different trouble, including swollen joints, sticking parts and mould. The Canadian Conservation Institute lists wooden wind instruments among the objects that can crack and distort when humidity is poorly controlled.

The families that depend on wood for their bodies, including the Violin, Cello, acoustic guitar, Clarinet and Piano, therefore share a basic rule: avoid extremes and sudden change. Keep instruments away from radiators, open fires, windows in strong sun and the interior of parked cars. For a wooden wind instrument in an environment that varies, the Institute suggests placing it in a polyethylene bag inside its case to soften the changes in moisture. Room humidifiers and similar devices are a separate subject, and a repairer who knows the instrument can advise on whether one is appropriate.

Brass: breath, moisture and corrosion

Metal wind instruments face a different set of hazards. The Institute groups them as prone to corrosion, denting and bending. Moisture from the player’s breath collects inside the tubing, where it is hard to see, and researchers who study historic brass instruments have observed that the internal humidity stays high long after playing stops. The general principle is to let an instrument dry and to clean it according to the maker’s or a repairer’s advice rather than leaving water and residue to work on the metal.

Surface care calls for restraint. Polishing removes a little metal each time, and a polished area reflects light differently from a matte one, so a dented Trumpet, Trombone or Tuba may look worse after cleaning than before. Mild tarnish can be removed gently, but the Institute advises consulting a specialist for severe corrosion. Moving parts such as valves and slides need only a sparing amount of suitable lubricant, with the excess wiped away, and a repairer can advise on the products appropriate to a particular instrument.

Strings under tension

Stringed instruments hold a great deal of force permanently. The strings of a concert grand piano together pull with many tonnes of tension, and even a violin is held together partly by the pressure of its strings on the bridge and of the bridge on the top. Climate changes the tension of every string and the geometry of every part that carries it. Swings in humidity therefore move the pitch and the tension together, and gut strings respond to moisture as well.

Sensible habits follow from these facts. Adjust strings gradually, since sudden large changes in tension can crack plates and loosen parts. Many repairers advise changing the strings of a bowed instrument one at a time so that the bridge and the internal sound post stay in place, although practices vary by instrument. Keep a piano in a room with stable conditions, away from heat sources and external walls, and have it tuned by a qualified technician. The Canadian Conservation Institute warns that tuning and maintenance of keyboard instruments call for specialists, and that not all tuners are sensitive to the needs of historic instruments.

Membranes and reeds

Animal skin behaves like the wood of a drum: it tightens in dry air and relaxes in damp air, so a skin-headed timpani, Banjo or hand drum will change pitch with the weather. Synthetic heads are far steadier. Players who prefer skin often re-tune before each use and keep the drum away from direct heat, since a head that dries too quickly can split.

Reeds are thin slips of cane, or of synthetic material, and they are sensitive to moisture and to physical damage. A reed for the Clarinet, Saxophone, Oboe or Bassoon can warp or chip if it is stored loose or left wet. Players commonly keep several in a ventilated holder, rotate them, and allow them to dry between sessions. Free-reed instruments such as the Accordion and Harmonica use small metal reeds, and they suffer when water and debris collect inside; leather valves and bellows on an accordion dislike extremes of heat and damp.

Storing and moving instruments

A well-padded case is the simplest protection. The Canadian Conservation Institute recommends keeping wind instruments in cases with good padding, and it also recommends checking stored instruments regularly, since objects out of sight are easily forgotten. Store an instrument in a room you would be comfortable in yourself, away from exterior walls, basements, attics and the path of direct sun.

Transport carries the most acute risks, which are shock, vibration, extreme temperature and moisture. The Institute’s published steps for shipping fragile objects begin by assessing the object and its route, continue by reducing the object’s vulnerability, for example by disassembling it where that is feasible, and then apply wrapping, cushioning (about twenty-five millimetres for basic protection and fifty for fragile or valuable items), and a suitable crate. Large keyboard instruments are heavy and have delicate detachable parts, and the Institute recommends professional movers for long distances.

When to call a qualified repairer

Basic care has limits. Interior cleaning, lacquer removal and any work on an instrument that is meant to be played should involve a specialist, according to the Canadian Conservation Institute, and the same applies to tuning and regulation of keyboards. Signs that professional attention is due include a crack or an open seam, a lifting bridge or fingerboard, pads or valves that stick or leak, a sudden buzz, a change in how the instrument responds, and any visible corrosion, mould or pest damage.

Repairers usually specialise by family, and historic or valuable instruments may call for a conservator who works to different aims. A maker or repairer repairs an instrument so that it can be played, while a conservator treats it so that as much original material survives as possible, and the two goals can conflict. If in doubt, stop playing, keep the instrument stable, and ask before applying glue, oil or any cleaning product yourself.

Terms used in this article

acclimatise: To let an instrument gradually reach the temperature and humidity of a new place before it is opened or played.
conservator: A specialist trained to stabilise and preserve an object while keeping as much original material as possible.
corrosion: The slow chemical deterioration of metal, accelerated by moisture and by salts or residues on the surface.
regulation: The adjustment of a keyboard instrument’s moving parts so that the touch is even and responsive.
relative humidity: The amount of water vapour in the air compared with the most the air could hold at that temperature, expressed as a percentage.
sound post: A small wooden dowel inside a violin-family instrument that links the top and back and helps carry vibration.