Zinc is a metal widely used in the construction of organ pipes. Even though it does not have the deserved exalted reputation of tin/lead alloys, it still has been used for more than a century for making the larger pipes in many instruments. Indeed, the largest metal pipes in the world are of zinc 5/16" thick; but it is not usable for pipes much shorter than 2' in length.
Zinc is not a material which the organ builder can process himself, and organ builders purchase it in sheets of varying thickness from rolling mills. In Europe, the zinc is softer and of a high purity. American zinc is generally harder from the purposeful inclusion of other metals.
When fresh from the rolling mill or polishing machine, zinc has a shiny, tin-like appearance, but it soon starts to look smoky or mottled and eventually turns grey. An interesting process of crystal growth takes place inside the zinc metal and eventually in hard zinc these crystals reach the surface of the metal and make a speckled or mottled appearance. The crystal specks are visible after about 10 years, and usually grow to full size within about 20 years. A look into any old American organ built before 1950 will show that all of the zinc pipes have completely crystallized and that the color of the pipe is dark and speckled. A twisting of the zinc metal will produce a crackling, scream, or shimmer as these crystals are broken away from each other, and the pipes appear to be hard or brittle.
Fortunately, the tone of the old zinc pipes is not audibly changed by this crystallization, and I have never seen an old zinc pipe which had suffered to any structural or tonal degree because of the crystals. Vandalism, careless servicemen or falling plaster are a greater threat, and many old tracker organs are restored with their 120-year-old-zinc pipes kept intact and speaking like new, or better.
Most zinc pipes receive a coat of lacquer. The lacquer may be clear if the pipes are used in the facade, but it appears that no clear lacquer is yet available which will fix the appearance of the underlying zinc, and after some years the once shiny zinc will become dark and irregular in appearance. Many zinc pipes are given a coat of opaque metallic lacquer so that the metal is totally hidden.
Zinc is used in organ building because of its low cost, ease of fabrication and acceptable but not thrilling tonal quality. I know of no builder who would claim zinc to be superior to a tin/lead alloy, but only a very few clients could afford to purchase a polished tin/lead Prestant 16', and not many more can even afford the luxury of an 8' Prestant in 90% tin, polished, with long feet and a fancy mouth treatment. The economics of organ building have kept zinc alive as a widely used metal, but in the face of a decline in the number of mills supplying the material, other materials such as copper, aluminum, and wood have found growing acceptance; the next 5 or 10 years may bring some changes in the type and amount of zinc used in organ building.