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Organ Pipes: An Enduring Application for Lead

Posted March 08, 2016 9:52 AM by Hannes
Pathfinder Tags: lead organ Pipe spotted metal

The water crisis in Flint, Michigan has thrown lead contamination (as well as poor government oversight and possibly corruption) into the public spotlight. While lead was once common in numerous products and situations, its associated hazards are now universally well-known and it's rarely used except in specialized applications.

One of these applications is organ pipes. Pipes manufactured in J.S. Bach's time were (supposedly) pure lead, but premium modern ones are made of a mixture of lead and tin known as "spotted metal." Pipe manufacturers use a tin/lead mixture for both tonal and practical reasons. Lead is pliable and prone to greater vibration when an air column passes through a pipe, resulting in a warm sound, but a pure lead pipe of even a short length of eight feet or less will collapse under its own weight. Tin provides the pipe with mechanical stability and lends a balanced brightness to the tone as well. Because each pipe is handmade and hand-voiced, the tin-lead composition is also soft enough that it can be easily cut and manipulated.

Pipes take on a spotted appearance when the tin:lead ratio exceeds 45% or so, due to the different melting temperatures of the two metals. As the liquid metal passes through its eutectic point, the metals separate and crystallize into small pools on the surface. (This video provides a nice basic overview of the manufacturing process.) These spots become more prominent as the amount of tin increases. Whereas spotted metal is the Rolls-Royce of pipe metals in terms of tone and stability, organ builders use other ratios and metals as well. "Common metal" pipes are also made of tin and lead but with tin concentrations of less than 45%, so that spots do not form. These pipes are cheaper due to the lower tin concentration, but don't sound quite as pure as spotted metal ones.

Organ pipes are often made using pure metals as well. Pure tin pipes are often used on audience-facing façade pipes because they boast the best aesthetic appearance and a bright sound. However, tin pest, a deteriorative condition affecting tin at temperatures lower than around 13° C, can spoil pipes if proper climate conditions aren't maintained. Pure zinc is strong and cheap and is used for long, low-pitched pipes, which consume more material than higher-pitched ones. It's generally accepted that zinc sounds duller than other metals, but its physical characteristics and low cost have made it useful to the present day.

As mentioned above, pure lead pipes were relatively common in many ancient organs, but even large ones have held up to this day. In the late 1970s organ builder John Brombaugh got his hands on some pure lead pipes from a Dutch organ manufactured in 1539. Surprisingly, his shop's analysis found that 16th and 17th century European lead contained impurities comprised of about 1% tin, .75% antimony, and trace amounts of copper and bismuth. These impurities provided enough stability to make the pipe feasible and enabled the rich, warm sound of an almost-pure lead pipe.

While they tend to get short shrift among some modern music lovers, pipe organs are marvels of engineering, most of them using antique technology with the vast majority of parts made and assembled by hand. Large organs contain thousands of pipes and a vast array of mechanical, pneumatic, and electrical control systems. Stay tuned for more organ discussion in future Notes & Lines posts.

Image credit: Freefoto.com

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#1

Re: Organ Pipes: An Enduring Application for Lead

03/08/2016 7:45 PM

Interesting... you would think that lead would be too soft to be used in a musical instrument, but it's the air inside the pipes that is vibrating, not the pipes themselves.

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Re: Organ Pipes: An Enduring Application for Lead

03/09/2016 12:02 AM

Do these high-Tin pipes eventually develop whiskers, like some of the lead-free Tin-based solders?

I gather that the materials used for making organ pipes are too soft to be used for hand-held instruments, and thus that brass is too hard for most organ pipes.

I donated a small pipe to the Spreckels Organ in San Diego, but didn't ask what it was made of...

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Re: Organ Pipes: An Enduring Application for Lead

03/09/2016 2:56 PM

I'm not sure about the whiskers--I haven't found any examples of that.

As far as the brass goes, horizontal organ pipes that aim straight at the audience are sometimes made of brass. Those are usually really loud reed pipes, so I'm not sure how much effect metal has on their sound or quality...it's the reed that does the sounding.

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Re: Organ Pipes: An Enduring Application for Lead

03/09/2016 3:50 PM

Yes, although they are plated, I think the trumpet rank in SF St Mary's Cathedral are brass. They are really loud, but I must confess I don't know whether they have reeds.

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Re: Organ Pipes: An Enduring Application for Lead

03/09/2016 8:17 PM

Organ pipes don't have reeds.

The air inside the pipe vibrates due to the Helmholtz oscillations set up as air passes past an obstacle (languide) as shown in the diagram below. It's the same principle as a flute or a whistle.

https://www.google.com/#q=organ+pipes

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#6
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Re: Organ Pipes: An Enduring Application for Lead

03/09/2016 11:04 PM

Sorry, but many organ pipes DO have reeds.

https://en.wikipedia.org/wiki/Reed_pipe

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Re: Organ Pipes: An Enduring Application for Lead

03/10/2016 8:06 AM

Thanks, I stand corrected. Learned something today.

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#8

Re: Organ Pipes: An Enduring Application for Lead

03/12/2016 1:07 PM

I can remember back in the 40's houses had lead pipes. I think some of the older homes still do.

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Re: Organ Pipes: An Enduring Application for Lead

03/12/2016 1:43 PM

Yep! At least one of the articles on the Flint MI situation pointed out that replacing a city's lead pipes with copper actually made the problem worse for those homes that still have lead pipes, unless there was at least a 10-foot section of Plastic pipe separating the lead from the copper.

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Re: Organ Pipes: An Enduring Application for Lead

03/12/2016 7:08 PM

Sebring, OH, has also had an elevated lead problem, but in only a few of the homes. These seem to have lead service pipe between the street and the home, but they have not mentioned lead pipe within the homes. The water tests fine when it leaves the plant, and in these homes IF they run the faucet for several minutes before taking a sample. Apparently the water is just a bit acidic and leaches lead from the pipe as it enters the home. The solution for them seems to be adding a chemical to make the water less acidic. I have seen no suggestion in the newspapers about replacing the lead service pipes in the few homes that still have them.

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