Organ Pipes: An Enduring Application for Lead

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.

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