Choosing the best and most durable materials is crucial for pipe organ building. For such a complex, delicate, and costly instrument as the pipe organ, investing in quality is a must.
Leather is an important ingredient in pipe organ building. Being a perishable material, its durability has always been a matter of concern. Indeed, it is a common belief that an organ needs to be re-leathered after 25 years or so, at very great expense.
At Ruffatti, our experience is quite different. The leather commonly used in organbuilding is processed for use in the clothing industry, with limited concern as to durability. Fratelli Ruffatti uses only leather which is tanned utilizing traditional methods. The difference is crucial: with traditional tanning, the leather retains its natural oils, which keep the material flexible. Rather than drying out and cracking where it is used as a hinge, or when it needs to inflate and deflate, the leather stays soft and flexible for a surprisingly long time. This is a lesson we have learned from restoring ancient organs. In many cases we find leather in almost pristine condition, after well over a century of use. At left, selecting the leather. The material is as soft as a fine glove, yet it is extremely strong, a very fine combination for pipe organ use.
In addition to utilizing the finest leather, we go out of our way to protect it from external agents, such as air pollution, that may contribute to shortening its life. In our conventional bellows, we build solid mahogany frames that completely seal the leather when the organ is not in use. Here again is a lesson that comes from our ancestors, who often used this technique in their hinged bellows to protect the leather from rodents, a common concern for churches in centuries past.
The most used and most critical material in pipe organ construction is wood. Wood is not only used for the visible casework, but also for all of the major internal parts, such as windchests, reservoirs, and supports, as well as for large and small wooden pipes. In particular, the windchests hold the mechanisms necessary to control the pipes.
It is common knowledge that wood is affected by humidity changes in the atmosphere. This can potentially cause severe damage to its structure, not only as far as the aesthetic is concerned, but also regarding functionality: pipes can stop playing, or can continue to play out of control. The risk of potential damage can be largely reduced by the proper choice and the proper treatment of woods.
At Fratelli Ruffatti we take all of this very seriously. For all of the functional internal parts we use Sipo mahogany, the most stable among the many varieties of mahogany that come out of Africa. Our attention to environmental issues is constant: we only utilize wood which is selectively harvested with rotation-cycle methods, allowing the natural regeneration of the forests. Above left, the selection of a Sipo mahogany log right after it has arrived on a boat from Africa. Above right shows the FSC certification stamp of the Forest Stewardship Council, which is on every trunk of mahogany that we buy.
The shrinkage-expansion ratio of Sipo mahogany is less than half that of other woods commonly used in organbuilding, specifically oak and maple, and, to an even larger degree, a wide variety of greenwoods. This means that the Sipo is potentially more stable. Also, its natural properties are emphasized by the way it is cut and seasoned. Cutting of the logs is done to our strict specifications, utilizing the “quarter sawing” technique, which allows us to obtain material of uniform structure.
The cut boards are placed on spacers to ensure air exposure for all surfaces. They are then stored in the open, and then indoors, for a total of five years to naturally stabilize and season the wood fibers.
Shrinkage coefficients for selected woods
(green to oven dry)
The Shrinkage and Swelling of Wood and Its Effect on Furniture
By Carl A. Eckelman
Purdue University – Forestry & Natural Resources
Cooperative Extension Service
West Lafayette, Indiana
Mahogany variety utilized by Fratelli Ruffatti:
Sipo Mahogany (Entandrophragma utile)
- Family: meliaceae
- Distribution: West and central Africa
- Growing environment: Moist deciduous forest, grows to height of 150 to 200 feet
- Shape: Straight, cylindrical. Diameter at base may reach 8 feet
- Naturally resistant to termite damage (unlike bass, birch, firs, maples, poplar, black oak, and red oak which are considered only slightly resistant or nonresistant to termites)
Sipo is the most stable among all the varieties of African mahogany. Since the values shown in the above table likely refer to average quality mahogany, these values may be even better for Sipo. All Sipo mahogany used in the Ruffatti workshop is Forest Stewardship Council (FSC) certified, coming from forests where sustainable forestry is practiced.
Extra measures taken by Ruffatti for maximum stability:
- Each log is personally selected from the importer’s lumberyard for exceptional straightness of grain and uniformity of shape
- They employ the quarter-sawing technique for all their logs for the optimal grain pattern within the lumber
All of the wood is naturally “seasoned” for 5 years before use instead of oven (kiln) drying which damages the cellular structure of the wood fibers.
Metals for Pipes
Tin and lead are the traditional components of metal organ pipes. Ruffatti prepares its own alloys according to the structural and tonal needs of each organ stop. But the starting point is always Malaysian tin and 99.99% pure lead. No better material can be found on the market. Below you can see ingots of pure tin from Malaysia.