Restoration process and options
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Planing a bridge cap |
Belly work involves:
Measurements and string removal
The plate, or harp, position is measured within the case cavity. Any changes in plate positioning here will affect the action later. Changes here may differ from factory positioning. Down-bearing adjustments are measured before and after the piano is unstrung. Side-bearing and string spacing due to bridge pinning is noted.
Soundboard
If the existing soundboard requires repair work, the old finish is scraped off the top and the instrument is covered in pads, heated and dried down to 5% moisture content. This is necessary because of our dry Minnesota winter. The ribs are reattached to the soundboard where they have separated. The glue joints are carefully inspected to ensure the soundboard is attached solidly all around the rim. The cracks in the old soundboard are planed open and seasoned spruce is inlayed into the board. Most of the spruce shims used are from old soundboards of the same era. The board is sanded and finished with varnish.
If a piano warrants a new soundboard, a tightly-grained Eastern Spruce soundboard panel (at 5% moisture content) is fitted to the rim with the grain oriented in relationship to the rim. New ribs are made from spruce. They are shaped to fit the inner rim mortises and sculpted for optimum balance and sustain. The ribs are often pre-crowned to accommodate the arc established on the inner rim. Once the ribs are glued onto the board (using either hide glue or Balduc wood glue which dries glass-hard), the soundboard is then allowed to expand to 8% moisture content. At this point the edges of the soundboard are tapered using a hand plane and calipers so that it acts like a drum. The bridges are introduced to the soundboard and the crown of the bridge is mated to the crown of the soundboard. Bridges are glued to the board and the final coats of finish are applied to the rib side. This assembly is dried down once more. Finally it is glued into the rim of the piano.
Remove and refinish cast iron plate
Initially the plate is inverted and a new pinblock is custom fit to the plate flange. The plate, is cleaned and sanded.
The first coat of finish is a red oxide primer, which is applied and sanded to 320 grit. The second coat is a combination of lacquer and bronzing powder, a mixture referred to as "gilding," which gives the plate its metallic gold color. New agraffes are installed and the plate is re-lettered. The serial numbers are reapplied and the wire sizes are printed in the plate webbing for the benefit of tuners who may need to replace a string. The final coat is clear gloss lacquer.
Re-surface and polish capo bar.
Re-felt cast iron plate.
Remove pinblock, fit and dowel in new block
It is critical that the pinblock be fit on all six surfaces. Tuning stability relies on this fit. The block is glued and doweled to the stretcher, and then screwed and doweled to the shelf. Balduc quarter sawn cross-laminated pinblock material is used.
Bridges
The bridge transfers the energy of a vibrating string to the soundboard. The string passes through two pins on the bridge to establish side-bearing, which keeps the string in place. If the string makes contact with a loose pin, a portion of this energy is lost. A string meets the front portion of the bridge just before it meets the back portion and then it deflects downward to the hitchpin on the plate. This is referred to as "down-bearing." Down-bearing is calibrated either through plate suspension or by recapping the top of the bridge with new maple and then planing to proper height. The new maple is drilled for new pins, notched for string relief and pinned.
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Completed belly work |
Fit plate to rim and suspend
Fitting the plate to rim ensures proper bridge side-bearing and bass and treble strike points. Correct plate positioning within the rim establishes proper action alignment to the strings.
Plate suspension is a height adjustment for proper down-bearing and string plane.
Clean and set nose bolts
These are shouldered bolts that pass through holes in the soundboard and keep the cast iron plate from heaving upward when string tension is applied.
Restring with 2/0 tuning pins
German blued tuning pins are preferred. Nickel pins are available upon request. International gold treble wire is used, and bass strings come from a variety of sources.
The new strings are pulled to pitch, the coils settled, the strings seated on the hitch pins and bridge pins.
Instruments with a duplex scale have aliquots or movable string rests between the bridge and the hitch pins in the plate. The segment of string from the bridge pin to these aliquots rings sympathetically. This gives the instrument more color and overtones. It is important that this segment of string be tuned to the rest of the instrument, which is done by moving the aliquots to create a longer or shorter segment of string.
Action work involves:
Replace hammers
Hammer selection depends on the instrument and the final tone that instrument is capable of generating. The best hammers for the job could be selected from a dozen different sources. (Steinway and Sons, Renner, Ronsen, and Able to name a few)
Shanks, whippens, and backchecks
Parts from the original manufacturer are preferred; otherwise there are good sources with high quality German parts available.
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Regulating a piano action |
Replace damper felt
Clean and polish damper blocks and wires
Re-bush damper guide rail
Recondition or replace damper back action
Install floating pittman through keybed
Replace let off punchings
Repair and polish ivory
This may involve matching and piecing ivory in from other keyboards. There is a collection of old ivory in the shop to make repairs that blend with the original as seamlessly as possible. If the ivories are no longer usable they are replaced with one-piece top and front German keytops. Ivory is no longer used in this country. Synthetic key coverings are available for today's pianos.
Dress and polish ebony sharps
Re-bush both key mortises
Felt selection and thickness is crucial in the key bushings. The key must move freely vertically with very little horizontal motion. Hide glue is used in this process so that steam may be used to remove the felt at a later date without damaging the keys.
Polish or replace key pins and capstans
Replace worn keyend and key frame felt
Size balance rail holes
The above processes all involve the original piano keys. If the keys are damaged past the point of repair, new keys are available. This may involve having keys custom fit to the key frame.
Space and travel all action parts
Bed keyframe forefinish action
These adjustments allow smooth shifting on the una chorda pedal and a solid foundation at the bottom of the key stroke.
Rebuild pedal assembly
This involves polishing or replating the pedal rods and pedals, rebushing the pivoting points, an assessment of the integrity of the return springs in the trap work and insuring proper fit for lyre braces.
Regulate
Regulation involves eight different adjustments for each of the 88 keys. The keyboard must be level with a slight crown in the middle. Key dip (the distance the key travels downward) is set. The blow distance (distance from the hammer to the string) is established. The let off - the point the hammer escapes the string - is established. The spring tension on the balancier is set. The backchecks (which catch the hammer after it hits the string) are regulated. The position of the jack under the knuckle is established. The balancier height is set. The drop screw adjustment is met.
Tune
A newly strung piano is chipped twice before the action is introduced. This means sounding the string by plucking rather than striking. This is done to put a load on the instrument. The treble wire is stretched, the action is introduced and the piano receives the first of a dozen tunings. New strings stretch considerably; they are constantly pulled up during this phase.
Voicing
This is the most crucial step in the restoration process. Voicing dictates the spectrum of tone, from crashing fortissimos to whispering pianissimos. After the strings are leveled, the next steps involve spacing hammers to the strings, shaping hammers by filing and mating hammers to the strings such that all three strings meet the hammer simultaneously. Hammers that are underpowered are stiffened. Hammers that are too bright are softened. A plucked string is the true tone bellied into that piano. Alterations to the hammers will either enhance that tone or distort it. Top quality work in this sphere requires years of experience. Recommendations are made for the selection of the hammers to be used according to what best fits the instrument's potential.
After the strings have settled on your instrument and released most of their stretch - a time period of six weeks to six months - a final voicing and regulating takes place in the space where the piano is used.
