Effects of Humidity on the Pipe Organ
Many pipe organ components are constructed with wood. Wood is affected by changes in humidity. Wood absorbs moisture in the air and expands when the humidity is higher; conversely, it will release moisture and contract when the humidity is low. Ideally, relative humidity levels should be maintained between approximately 30% and 60%. A moderate level of humidity also helps maintain the suppleness of the leathers and other flexible materials within the organ.
If proper care is not taken, low humidity can place stress on wood parts. This stress can cause wood to crack or split. Extended and extreme low humidity or a sudden drop in humidity can cause wood to split. A split in a wood pipe can adversely affect speech or even render a pipe “speechless”. A split in a windchest can cause seasonal or permanent ciphers, slow or dead notes, or multiple adjoining notes to play together.
Often, artificial heat will dry the air to a very low level of humidity. In these situations, lowering the temperature when the room is not occupied can help maintain a reasonable level of moisture in the air. This protects not only the pipe organ, but other wood furnishings as well.
Room-sized humidifiers are generally ineffective and not recommended. Too many times we have seen the damage caused by localized humidifiers. Humidification systems for the entire building are recommended.
Excessive humidity can be detrimental, too. Swelling can cause wood to warp. High humidity can cause metal components to corrode and mildew to form on various components. Most modern buildings with air-conditioning do not have issues with high humidity.