Piano Rebuilding


Rebuilding is the process by which a piano is improved through evaluation of its existing condition and a subsequent plan of repair procedures formulated and performed to complete its restoration. While usually thought of as a total restoration, rebuilding can involve any number of repairs to restore the piano to various levels of performance and appearance. A rebuilding is normally divided into two main categories: refinishing and technical rebuilding. Refinishing involves refurbishing the piano case along with case parts such as the lid and fallboard, brass hardware, and bench. Other miscellaneous parts that are disassembled from the piano are also refinished to give the piano a consistent appearance.

The technical rebuild can include repairs to the action components and restringing with new strings and a new pinblock. Also addressed is the condition of the soundboard and bridges. These two main areas of work are then planned to ensure the most efficient work flow in the rebuilding workshop.

Evaluation is the first step in the process. The technical aspects and finish condition are assessed for various repair needs, both individually and in relation to each other. Because of the dual nature of the piano—furniture and musical instrument—the intertwined relationship must be considered to make the restoration complete and cost effective. For example, a pinblock cannot be repaired without restringing the entire piano, and, if a plate is removed for pinblock work, consideration should be given to plate refinishing while disassembled, even though this was not originally a high-priority item in the restoration, since the opportunity might not become available again for many years. These peripheral procedures, if overlooked, can diminish the benefit of the work that is completed.

With the above overview in mind, individual items are now evaluated to plan the restoration. These include:

• Finish • Hammer Butts
• Case Assembly • Knuckles
• Bench • Treble Bridge
• Key Bushings • Bass Bridge
• Wippens • Downbearing
• Action Centers • Soundboard
• Bridle Tapes • Ribs
• Touchweight • Strings
• Action Felts • Tuning Pins
• Back Checks • Pinblock
• Hammers • Relative Pitch
• Dampers • Voicing
• Regulation • Pedals
• Damper Guide Rail

There are many subassemblies within the items listed above that should be considered during a complete repair.

After the evaluation, parts are ordered that must be custom made for the individual piano. This would normally include bass strings that have copper or, in older pianos, iron windings; the pinblock, which must be custom cut for a proper fit to the plate; hammers that may have a unique set of bore coordinates; and bridges that are made from original samples. Some repair facilities have the necessary equipment to customize the above parts from stock selections. Other repair shops will send these parts to specialized supply houses for duplication. Many items used in repairs are standard parts that can be kept in the shop inventory to facilitate faster repairs. Some of these items include case felts and protective rubber buttons, casters, keytops, bridle tapes for vertical pianos, damper felts, knuckles, tuning pins, and treble music wire in the common sizes.

The finish work will proceed while the custom parts are manufactured or purchased. Numerous components in a piano must be refinished or cleaned before assembly. The down-time while awaiting technical parts provides an excellent window of shop time for aesthetic case refurbishing. Typically, the case and case parts such as the lid, fallboard, shelf and desk, and so on, are stripped of the old finish so that a new stain and finish can be applied. The cast-iron plate is sanded to provide a suitable surface for rebronzing or relacquering in traditional gold tones. The soundboard is scraped or chemically stripped of the old finish in preparation for a new finish application.

The refinisher will encounter many conditions in the existing finish that will dictate the correct course of action. Typical defects or effects of age include bleached or faded finishes, orange peeling in the finish, flaking chips of old finish material, blistered veneer or finish, and checking finish.

Depending on the defects, the refinisher will determine if the existing finish can be improved. If the finish condition is too severely damaged, stripping and refinishing is the recommended procedure. After the components have been stripped, they will undergo successively finer grades of sanding to accept the various coatings that provide a finished appearance. Fillers, sealers, stains, and protective top coats will be applied after the prescribed sandings.

Refinishing a grand or vertical piano requires a sequence of steps that will provide the best possible results with an optimum use of shop time. The piano is disassembled into smaller components. Grand refinishing may include removal of the plate if pinblock work is needed for the technical restoration. Pinblocks are seldom replaced in vertical pianos since the procedures are more extensive and the lower resale value of a vertical in comparison to a grand usually does not justify the cost of replacement. These smaller case parts (sometimes called fly parts) and the case are stripped either chemically or by sanding. Hardware such as brass hinges and pedals will be cleaned and polished if the original parts are to be reused.

Minor repairs will often be necessary on pianos undergoing rebuilding. Case defects, such as dents in the finish and missing veneer, will be corrected. After finer grades of sandpaper have been used to prepare the surface, a stain is applied that will accentuate the grain of the wood used in the face veneer of the cabinet. Some pianos will have an opaque finish, usually white or black. These opaque finishes will not require a stain, since the grain is hidden by the pigments in the finish.

A wash coat is applied to the stained wood to raise the small fibers of the wood. These fibers are sanded to provide the smoothest surface possible. After sanding the wash coat, a filler is spread to fill the remaining open grain. The cabinet is sanded again to remove any excess filler. A sealer must be applied to seal in the filler and to prepare the wood for the finish coats.

Lacquer is the most common finish coat used today because of the fast drying time between coats and the durability of the finish. Other finishes are sometimes used depending upon the desired finished effect. These include polyester or polyurethane, varnish, and shellac. After the finish coats are applied, the finish is rubbed with steel wool or very fine sandpaper to achieve the desired sheen.

Simultaneously, the technical restoration is in process. This is usually broken down into the broad categories of action rebuilding and restringing. Soundboard replacement and pinblock replacement can be viewed as expanded procedures in restringing. Action rebuilding approaches the touch and tone capabilities of the piano in relation to the playing mechanism. The various components that comprise the action are scrutinized for weaknesses that will diminish the tone and touch of the piano. Hammers are commonly replaced with new. As a hammer is played, the felt that comprises the surface of the hammer can become compacted and distorted in shape. Older hammers can be reworked or reshaped if sufficient felt remains on the hammer surface. Shanks and flanges are also replaced if the bushings on which they pivot are worn beyond repair.  Wippens are also replaced if springs are rusty or if the bushings are severely worn, though wear is usually not as advanced as in the hammer flanges.

Damper felt can become grooved, flattened, or crusty, thus necessitating replacement. The wooden damper heads are normally reused, as are the damper wires and damper flanges, though a very complete restoration will include replacement of these flanges.

After replacement of the action parts, the action is thoroughly regulated. This is the adjustment of the action parts to prescribed specifications to provide the best touch response and repetition.

The keytops are normally replaced with new ones, although older keytops made of real ivory can be bleached and polished to new condition. This is often desirable if the original ivory has not been chipped beyond repair. Key bushings are also replaced to prevent a loose, wobbly feel to the pianist. Balance-rail felt and front-rail felt is replaced with new and is sized with the proper cauls for optimum fit over the key pins.

The soundboard is either replaced or repaired as necessary. Repairs will include shimming or filling any cracks that may have appeared within the spruce planks. The soundboard should have a crown or upward bow in its surface to provide the best resonance. If the crown has flattened, the board can be replaced.

The plate is reinstalled in the piano after finishing work is done. At this point bridge work and soundboard repairs have been completed and restringing can begin. In the past, the choice of string sizes was based on duplicating what was taken out of the piano during breakdown. Unfortunately, this prepetuated any scaling discrepancies that may have been built into the piano during manufacturing in previous decades, when the physics of piano design was less understood. With research and the introduction of the computer, string scaling has become much more refined than in the earlier days of manufacturing. This technology has introduced the capability of taking the existing string lengths and design parameters of a given piano and developing an improved scale that is more balanced and more tunable than the original scale. This can produce a significant improvement to pianos that were manufactured in an earlier era by smaller firms that were undercapitalized and could not spend large sums on research and development.

The piano is reassembled after the stringing and subsequent tunings. It will undergo final regulation and voicing, along with final case assembly and hardware installation, before being inspected and released for shipment back to the owner.

The art of piano rebuilding has progressed, as has the art of piano building itself. With today’s better understanding of piano technology, restoration of older instruments can be approached with the goal of improving the design of the original piano by utilizing the methods and data currently available. In many situations a restoration can be a viable alternative to purchasing a new instrument. Careful analysis of the existing condition and the potential of the prospective piano to be restored are the most crucial initial steps in determining the costs versus the benefits of a piano restoration.


Reference:  Piano An Encyclopedia, Second Edition