The Manual of Musical Instrument Conservation by Pollens Stewart

Author:Pollens, Stewart [Pollens, Stewart]
Language: eng
Format: epub
Publisher: Cambridge University Press
Published: 2015-07-30T23:00:00+00:00

Pipework

Organ pipes are readily damaged by careless tuning and rough handling, especially when organs are disassembled or moved. Before working on pipes, one should examine them closely to determine if they were made by the same hand and whether inscribed note designations correspond to the notes the pipes actually play. It is important to make this assessment, as pipes are often cobbled from other instruments or transposed upwards or downwards to alter the pitch. Also check for alterations in the pipe mouths, as they may have been cut up or the pipe may have been disassembled and recut so as to lower the mouth.

Pipes are made of various alloys of tin and lead, though bismuth or antimony are sometimes added for stiffness. Because of its low cost, sheet zinc has sometimes been used to make larger pipes. Sheets of tin/lead alloy pipe metal are formed by pouring the molten metal into a trough that is drawn along a casting table. An adjustable slot in the trough allows the metal to pour out in a uniform thickness. In some schools of organ building, the casting table was covered with cloth, and one can see the cloth pattern on the inner surfaces of the pipes. Because the melting point of pipe metal is lower than the burning point of cloth, the cloth did not scorch. After the metal cooled, it was peeled off the casting table. Pipe metal was sometimes hammered to increase its density and stiffness and to reduce thickness. Today, drum planers are often used to reduce metal to the required thickness (the parallel marks made by their cutters are clearly recognizable). While drum-planing reduces thickness, it does not impart the same physical changes that hammering does. Pipe metal is sometimes stored at room temperature to “season” it, which causes it to become stiffer. Special temperature-controlled ovens are sometimes used to accelerate this seasoning through a process termed precipitation heat treatment. To construct pipes, tables or graphs of dimensions are consulted when marking out the various components (such as the resonator, foot, languid, etc.) on the sheets of cast metal, which are then cut out and soldered together (see discussion of pipe soldering below). Wood pipes are joined up with hide glue and clamps in the usual manner.

When handling pipes, gloves should be worn to protect the metal from perspiration, which has a corrosive action due to the presence of oils, lactic acid, salt, and moisture. Pipe metal is quite soft and must be treated with great care. Typical damage includes general shape distortion, dents, open seams, tears due to excessive or improper tuning, misshapen mouths and displaced languids (either from manhandling or abortive attempts at voicing), as well as dirt and corrosion.

If pipes are removed so that work can commence on other parts of an organ, or when an organ is moved, pipe trays should be made to store the pipes safely. Cleats should be fastened to the sides of the trays to prevent the trays from falling into one another when they are stacked.

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