Aluminum has been commercially available as a metal for only 100 years. Previously it was so rare, exotic and precious (at $90 per pound) that it was even chosen for the point at the top of the Washington monument. The price is now much lower. With some new fabrication techniques, aluminum is being developed as a metal for organ pipes.
In the 1940s organbuilder Charles McManis pioneered the development of extruded aluminum organ pipes. Difficult to solder or weld, the material was problematic and saw only limited use.
In the 1960s the late Gerhard Beisecker patented a method of joining aluminum seams on the backs of organ pipes, but the system was less than permanent and the idea became a dead end in aluminum pipe development, even though some ranks were sold and installed.
The technical advances in welding aluminum are responsible for a resurgence of this metal and, for the first time, organ pipes of aluminum have been fabricated with an all-welded construction. Unfortunately, the appearance of the welds on aluminum pipes is not as clean, smooth and small as on tin/lead, zinc or copper, and many builders await an improvement in these welding techniques before such pipes are acceptable. Important advances in weld appearance have recently been made.
A very interesting and important development has been the polishing of aluminum pipes to the point that they rival polished tin in appearance. The long-term stability of this type of polishing (preserved by the instant formation of the clear aluminum oxide skin on the metal) appears to be very good, and aluminum may be the only material to match the long-term appearance of tin for facade pipes.
Naturally, any new material will find slow acceptance, simply because it is not the standard tin/lead alloy, but many recent successes in aluminum pipes are attracting attention with the cost of high-tin facade pipes high enough for only a few clients to afford.
My own use of polished 16' aluminum prestants for two recent large tracker organs has been satisfying both visually and tonally, and I believe that this is the first installation of such large polished aluminum pipes anywhere, though other builders have used aluminum pipes both inside the organ and en façade.
For some, the sound and appearance of these 16' ranks will rival that of tin in the upper octaves, while others will certainly claim that I have a tin (or aluminum) ear. Certainly, refinements will come as the parameters of the sound and structure of the material are further investigated and developed and a variety of types of pipes are tried with this material. Some builders will find aluminum to be unacceptable for pipes.
An interesting development is that aluminum seems useful as a material even for rather small pipes; far beyond the place where one would normally change from zinc to tin/lead, it is possible to build and voice aluminum pipes which are excellent in sound. The extension to very small pipes is proceeding in a developmental stage, but the results must be startling.
An apparent disadvantage to the all aluminum pipes is that all constructional features must be done in aluminum, including ears, hooks, and miters; and, unless special welding equipment is available, physical revisions or additions to the pipes cannot be made, or would be difficult to make. Doing a miter "on the job" is pretty much out of the question. For the builder using aluminum pipes, every detail should be worked out carefully in advance. For best results, a high purity aluminum produces a pipe which is soft and strong. Alloyed with other metals, the aluminum becomes harder and more rigid, but even the softest available material seems adequate for supporting the largest pipe (one man can easily lift a 16' aluminum prestant). It is the near deadsoft character of the metal that brings it closer to tin/lead in sound than either zinc or copper usually does, though this certainly may be disputed by other builders.
Justin Organ Pipes of St. Paul, Minnesota have made all the aluminum pipes we use.