Most musicians are aware of the problems caused by fluctuations in relative humidity when an instrument is constantly being moved between locations and venues - some of which are artificially heated or cooled and where relative humidity can reduce to dangerous levels. Wood is an hygroscopic material, in other words, it absorbs and loses moisture as relative humidity changes. It expands as it absorbs moisture and shrinks as it expels it.

Musical instruments can usually cope with the speed of humidity changes that occur naturally. Artificial environments such as the air conditioning in aircraft cabins and concert halls present a problem, as the sudden moisture loss and consequent shrinkage can put the instrument under stress that it's not able to cope with and cracks can appear in the plates.

Placing a humidifier in the instrument case or actually inside the instrument can help to prevent this type of damage. Humidifiers gradually release moisture into the surrounding air.

Many players will be familiar with the "Green Snake" - the green rubber tubing with the sponge insert which is immersed in water then inserted through the "f" hole of the instrument. This is an effective humidifier and many players find no problems in leaving this in the instrument whilst they are playing. They need to be soaked, probably on a daily basis, when conditions demand and players must be sure to wipe excess moisture off before insertion into the instrument. This is extremely important as, in general, violins themselves do not like to be soaked and precious maker' labels, signatures or stamps could be damaged by coming into contact with free water.

There is also a new product on the market which will help. A Swiss chemist has developed a new product, called Hydro-Polymer, which has an amazing ability to absorb water. Hydro-Polymer resembles grains of ordinary table salt and, when in use, raises the relative humidity in the instrument case. It is stored in a porous nylon pouch designed to release the humidity in a regulated manner. This product, known commercially as "Stretto", is activated by soaking the porous pouch for ten minutes in distilled water (which doesn’t leave minerals or impurities behind when it evaporates). It then goes into a plastic holder that attaches with velcro to the inside of a case and will release moisture into the air for up to two weeks. It can also be purchased in a kit, which includes a digital thermometer and hygrometer so you can monitor the relative humidity in the case with greater accuracy. This is the key to understanding when your instrument may be in danger.

Properly applied and monitored, either of these humidifier systems (or a combination of both) should help maintain a safe level of humidity (40 - 60%), thus helping you to protect your precious instrument and bow from possible damage.