A big part of piano restoration is aesthetics. How a piano looks is a major attraction to piano owners. Piano rebuilding is as much about making the instrument looks nice as it is correcting mechanical deficiencies. It is somewhat hard for me to admit that, since I hold high the value for good sound and functionality above appearance, but it is a fact. Many modern pianos are sold based on shinny finishes and a new looking interiors yet lack quality construction that truly makes them wonderful instruments.
An area of aesthetics to be concerned with when restoring a piano is the cast iron plate, sometimes referred to as string frame or harp. The plate is a major component within the structure of a piano and is the main contributor to the dynamics and sound of a modern piano. It is big, it is heavy, and it is beautiful!
The early forte piano of the classical period differed from the modern piano in tone and dynamics. With low tension scale designs the forte piano was very quiet; used mainly in small chamber halls for recitals. It wasn’t until the invention of the cast iron plate (Alpheus Babcock, circa 1825) that the piano became the center piece of the modern stage and symphonic orchestra. As audience size increased and large auditoriums became the norm the demand for a piano with more power was imposed upon piano makers worldwide. The only solution was to increase tension, and therefore wire diameter, across the scale of the piano. The plate was paramount to achieving this.
Modern pianos contain upwards to 40,000 pounds of torsion as well as nearly 1,000 pounds of downward pressure on the soundboard. The cast iron plate not only supports string tension but also provides structural integrity to the piano rim supporting both string tension and string downbearing.
Early piano plates where casted in sand molds, an art form of its own. As a result surface areas of plates are generally rough, requiring filling and painting. Rebuilders are faced with the challenge of resurfacing plates, removing any chips, scratches, and other blemishes that occur over the years.
Different terms are used to describe this work such as: re- bronzing, refinishing and repainting. In reality, the original plate must be surface sanded, filled as needed, and prepared for a new finish. At Grand Workshoppe we used modern catalyzed acrylic enamel automotive paints.
The following images will illustrate our process for repainting a piano plate:
Cleaning a Piano Plate
The first step in refinishing a piano plate is cleaning. Being a horizontal surface the plate acts as a collector of dust, polish over-spray and environmental contaminates. Washing will prepare the plate for surface sanding. After washing the plate is air dried to remove moisture and deposits of dirt and grime.
Surface Sanding the Plate
The surface of the plate is sanded with 320 grit automotive grade sand paper to remove any residue form washing, blemishes, and to level out chipping. Notice the black under coat. This is the filler/sealer used to smooth the plate after casting.
Preparing the Plate for Painting
Once the plate has been surface sanded a solvent is sprayed over the original finish. Generally I use the same solvent recommended for the type finish that I will apply. I feel this helps the new finish bond with the old.
Painting the Piano Plate
The first coat is applied as a fine surfacing agent to assure adhesion. Once this dries to a tacky touch heavier multiple coats are applied.
Newly Painted Piano Plate
The plate is considered done after multiple coats have been applied and consistent coloration is achieved.
Lettering a Piano Plate
Piano makers adorn plate surfaces with their branding, patent dates, and other proprietary information. All raised surface decorations are painted in black unless specific maker branding dictates otherwise.
Reconditioning Piano Plate Hardware
Screws and bolts used to mount the plate to the rim are generally in excellent condition. Each piece is removed and placed in a template to assure that they are returned to their original position. The old finish is removed with a wire brush wheel. Photos show damage done to screw heads as the result of having been removed carelessly years earlier with an improper screw driver. Once damage is done these screws are hard to replace since they can be anywhere from 80 to 120 years old. Regrinding the screw heads was necessary in this case.
Screwing the Plate into the Piano
This image shows the plate webbing screws being reinserted into the new pin block. Notice how the heads of the screws have been resurfaced as shown in previous image. Screw installation is done by hand using a well-fitted driver bit.
Brass Nose Bolt Caps
Functional and decorative, brass nose bolt caps are polished to look like new. Solid brass has the potential to be renewed with polishing. These caps in particular had been damaged by a previous removal. Fortunately, since they are solid brass they were able to be restored.
Piano Restrung with Plate Refinished
When it all comes together with new felt, steel strings, copper wrapped strings, soundboard, bridges, and repainted plate, the interior of a grand piano is even more striking than the exterior; truly a great invention of aesthetic beauty.