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headcase

Humidifiers

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Just to prove the old adage, 'you can learn something new every day', I visited a very nice 1904 Hunter organ today, to which a humidifier has been fitted.  Aside of the usual trunking into the wind system to distribute humidified air into the soundboards,  there was a further feed to a 4" diameter metal trunk, about 3-4ft long, with a series of  holes along the length of it,  projecting humidified air into the air space beneath the soundboards.  This struck me as eminently sensible - a bit of space humidification - yet in 39 years in the trade, I've never seen it done before.  

Any one else ?

H.

 

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Liverpool Cathedral and Georgie Hall both have external humidification feeding into each swell box.  Given humidity is usually around 30% every little helps!   LC has two W&W D16s per side and SGH has one D16 each side - glad I'm not paying the water bill!

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I have seen village church organs in which a bucket of water is left to evaporate to provide humidity. In my church any music left on the organ for more than a day or two becomes damp and musty and such a bucket would gradually fill rather than empty...:wacko:

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Not just village organs!  As well as a humidifier plant we have 3 large seed trays filled with water under the main frame of a 4 manual organ. The church heating is maintained at 22deg. at the weekend & reduced a couple of degrees during the week. This used to play havoc with sliders sticking but since the addition of the trays we have had no problems at all. I got some funny looks though when I placed them in the organ chamber & was then seen carrying several full water cans!

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Low humidity is clearly an issue.  But humidity which is too high brings with it another set of problems to do with bacterial and fungal growth, which could have major consequences for the wood and leather work in an organ action.  I mention this having experienced it myself in a domestic environment.  Many years ago we had double glazing installed in our home.  Prior to that the internal humidity level went up and down in response to the weather outside and this was particularly noticeable as the seasons progressed each year.  One result was that the internal woodwork (e.g. door panels) expanded and contracted like a concertina, the wood swelling in autumn and contracting again the following spring.  So the solid wood doors would stick in winter but not in summer - it was a predictable and highly noticeable effect.  I remember thinking more than once "no wonder organs have humidity problems"!   But after the double glazing was installed the concertina effect virtually disappeared, to be replaced by really bad problems to do with mould growth on walls etc.  Sometimes we had to physically wipe the water off some walls.  Apart from anything else, the mould was a potentially dangerous environmental health hazard.  It occurred because the new windows created a virtually sealed environment from which water vapour could not easily escape, though it was surprising how long it took for me to arrive at this conclusion.  Thus the humidity rose to around 100% and stayed there, but without a hygrometer this was not immediately apparent.

After trying lots of things including DEhumidification (!), the solution was to retain a modicum of moisture in the internal atmosphere but to control it by monitoring a couple of hygrometers installed upstairs and downstairs.  (When first brought into the house they almost went off-scale).  Thus we now have what is essentially a closed-loop humidity control system, with me being the human servo-actuator who has the job of slightly adjusting the amount by which we open the window ventilators every few days or weeks.  I find a humidity level around 60% is about right.  This simple measure has dramatically reduced the bacterial/fungal growth problem to negligible proportions and it also more or less stops the annual oscillation in the woodwork.  Incidentally, I had to discover this solution for myself - it wasn't mentioned in an expensive report which I commissioned from a so-called expert surveyor, whose services were completely useless.  And the time it took to find the root of the problem was not because I was an idiot (even though I might be), but because anything you do in this situation has a very long time constant - you have to wait weeks for the effect of any change to become apparent.

So perhaps a conclusion here is that it is necessary to have some sort of humidity controller installed as part of the humidification installation, either automatic or (as in my domestic example) manual.  Otherwise there might be a danger one set of problems will be exchanged for another.

CEP

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Good point, Colin.  All the organ humidifiers I have encountered are controlled by  a Humidistat, typically set to 55-60%.  Chest magnet armatures can be vulnerable to over-enthusiastic humidification. The leather gasket can separate from the metal disc.

H.

 

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5 hours ago, headcase said:

Good point, Colin.  All the organ humidifiers I have encountered are controlled by  a Humidistat, typically set to 55-60%.  Chest magnet armatures can be vulnerable to over-enthusiastic humidification. The leather gasket can separate from the metal disc.

H.

If a humidifier is fitted, all soundboards should be fitted with bleed valves to control this type of problem.

 

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Wide variation in humidty made a substantial contribution to the problems with the HWIII organ at Holy Trinity Bradford on Avon.  An organ in a church on a flood plain does not have ideal conditions; the relative humidty along the Avon valley can go up to 90%, never mind floods and leaky roofs

Heating and vicious drafts tended to dry the organ out, and at one point the Vicar resorted to galvanised zinc flower trays inside the organ to rehumidfy it.  Eventually a humidifier was installed.  A new oil-fired heating system gave wide fluctuations inside the church and uninsulated heating pipes passed through the blowing chamber.  The final straw was a hot-air heating system installed against the advice of the then organ tuner (John Coulson) and the organist. 

The sad effect was to ruin the Pitman chest action in the organ.  Even if it had been renewed when suggested in the early 1970's it would probably have required another renewal as no attempt was made to tackle the basic problems until very recently. 

The Society for the Protection of Ancient Buildings (SPAB) is a good source of advice on the right degree of humidity and associated problems. 

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