Sesquialtera

by Colin Jilks

"A process, which although slow, is relentless and unstoppable"

Many of our greatest composers and artists have, quite rightly, acquired a degree of immortality through their work and undoubtedly J S Bach is pre-eminent in our organ world. The literary world has William Shakespeare: witness John Milton writing in 1630 "What needs my Shakespear for his honour’d Bones". Even some of our more modern writers have left a legacy in their fictional characters. For example, there is P G Wodehouse’s Jeeves with the ever-youthful Bertie Wooster and Sir Arthur Conan Doyle’s Sherlock Holmes and Dr. Watson, brought to life in A Study in Scarlet. Holmes is a fictional character who has surely gained immortality in readers’ imaginations. For it seems that as we close the book and switch off the light, he rises from the page ever awake, stepping silently from the room out into the fog-bound labyrinthine night.

But I digress, although I do wonder if immutable apparitions of past organ builders might still haunt our churches, as their work was in such abundance during this Victorian period of 1880-1900. In fact, the William Hill organ I have played for many years was built in 1881; the same year Holmes began his adventures. Have I encountered the ghost of Renatus Harris I wonder? Well, perhaps not, but when tuning and regulating his precious organ pipes, handcrafted by flickering candle light in 1695 for the organ at St. Clement’s Church, Eastcheap, it’s difficult not to feel some affinity with their maker.

Many fine organs have been built, but built for different times when conditions were quite unlike today. The fog-bound nights of the 1880s were not unusual and church heating was primitive, which suited these instruments, their well-seasoned timbers remaining stable and undisturbed. But as they live on they must endure the modern congregations’ penchant for carpeted warmth and comfort.

An organ’s timbers that have stood the test of time have to face new unpredicted challenges. Last winter was a period of exceptionally low rainfall in the South of England. Drought conditions, especially the period from January 2006 until early May, resulted in unusually and exceptionally low relative humidity levels in our churches and concert venues. The far reaching and debilitating consequences have not always been fully appreciated as the effects are not immediately obvious until it is too late, which leads to misconceptions and misunderstanding.

Organs are constructed using a variety of materials, but mainly timber. Timber, no matter how well seasoned, has a natural moisture content which is required if it is to maintain its structure and dimension. Any significant change in the humidity in the surrounding atmosphere will cause the timber to shrink or expand in line with the atmospheric moisture levels in its surroundings. The timber tries to attain, and retain, a moisture equilibrium with its encircling atmospheric environment, a process, which although slow, is relentless and unstoppable.

Normally an average outdoor relative humidity is about 65% to 75%, which is similar to that in an unheated church. But during the winter, especially with freezing temperatures, the humidity levels can drop much lower. We know that air expands when heated, and here is the cause of our problem. Cold, near freezing, air brought into a building and heated to a normal indoor temperature of some 65f, expands dramatically. Its expansion results in its relative humidity dropping to incredibly low levels — the same amount of moisture but in a much larger volume of air. Readings as low as 32% relative humidity were recorded in some of my London churches last winter. Any humidity level below 55% is undesirable and can be positively dangerous to organs.

A Modern Organ Humidifier

Damaging stresses may develop in the organ’s soundboards or pneumatic action timbers, even the building frame on which the organ is constructed will change shape shortening or lengthening tracker runs or prematurely exhausting pneumatic actions with fearful consequences.

Modern humidification plants designed for use in organs can partly alleviate these problems and are especially beneficial for older organs. Organ builders recommend these humidifiers for instruments in buildings with constant central heating. Humidifiers are, in essence, large water cisterns with a constant mains water supply, a paddle and fan. The paddle throws water up on to an internal basket of pumice stones, which absorb the water and the fan passes air over them humidifying the air. This humidified air is then introduced by wind trunking into the organ’s wind system allowing moisture to reach almost all internal parts of the organ; also, fitting strategically placed exhaust valves allows the newly humidified air to displace the harmful dry air.

The effects can be dramatic, especially with pneumatic actioned instruments; it has been possible for some of these organs to be brought back from the brink of apparent oblivion. But, regrettably, not all parts of an organ require such a high humidity, especially some leathers in organs, which require more sensitive treatment. Organs of differing action and design require individual attention, but with careful maintenance can still work well under difficult conditions. The secret is to humidify the organ to the level preventing the organ’s timbers drying and distorting. Too much humidity can cause the encouragement of moulds and rot, which undermine glues and joints.

It would be imprudent to expect modern church congregations to endure the conditions of the 1880s, but with the assistance of modern technology, some form of immortality will remain for our historic organ builders, preserved for future generations. Before an instrument is condemned, its environment should be considered and appropriate action taken. A new humidification plant can be expensive, but in no way as expensive as a new organ.

 

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