Steinway, Baldwin and Mason & Hamlin Piano Plates
The Piano Plate
The cast iron plate is the single heaviest piece in a piano. Traditionally painted in a golden bronze color, it is one of the most visually striking components of any grand piano. The plate’s function goes beyond the cosmetic. A carefully cast frame, this large piece of cast iron sits above the soundboard. Its purpose is to absorb the lion’s share of the over 40,000 lbs of tension produced from the hundreds of piano strings. Early pianos lacked iron frames and therefore were unable to support high string tension. The introduction of cast iron frames helped transform the piano into the powerful instrument we know today.
Steinway Plates
Most often made of cast iron, each manufacturer has its own special metal composite for their piano plates. Steinway & Sons uses Class 30 gray iron, a particular combination of metals unique to Steinway. The O.S. Kelly Foundry in Cincinnati, Ohio has made plates for Steinway & Sons since 1938 and is now their only North American supplier. The Foundry casts thousands of plates each year for the company’s New York built pianos – each one completed utilizing time-honed, labor-intensive methods.
“It’s like a secret recipe for manufacturers. They carefully guard their particular (mixes) because composition of the plate actually affects the tone of the piano.” – Daniel Chupp
Only years of research provide just the right mix of materials. This is important because the composition not only affects the strength of the plate but the tone of the piano as well. The resonance of the metal plate affects the character of the piano’s tone.
Traditional vs. Modern Forms of Casting
Steinway and other similar high-end piano manufacturers utilize sand casting to mold their plates. It’s an old-fashioned method that requires a lot of time, work, and resources. Molds are made from chemically treated sand which hardens around a master form. When the form is removed, the hollow space inside is filled with the molten iron mix which is heated up to 2000° F. When it cools, the sand is broken off to reveal the newly cast plate. To ensure that the plates utilized in their pianos would continue to be done in this traditional method, Steinway recently bought the O.S. Kelly Foundry. A more modern form of forming these iron plates is the vacuum casting technique. This method is utilized by many large manufacturers including Yamaha and Kawai. While vacuum casting is more efficient, can create smoother plates, and is less expensive when done en masse, some piano purists maintain the old method helps produce a higher quality of tone.
Hand Painting | The Final Touches
Once casting is complete, the plate is sanded and any voids in the casting are filled. Primer is first applied and then multiple coats of gold paint are sprayed over the plate. After this finish is built up to the appropriate level, a clear coat is sprayed to protect it. Steinway, like many other piano makers, adorns their plates with various trademarks and company insignia. The raised lettering is expertly hand-lettered at the factory. Although purely cosmetic, this helps put a finishing touch on every piano. The difference is always in the details.
After the plate has been finished, it is set into the piano’s case. Once the proper plate height is achieved, dozens of bolts are tightened down to hold the massive plate in place. (Setting the proper height is important as it greatly affects the down bearing.) After the plate has been installed, the piano is strung and the strings are pulled up to tension.
Installing The Refinished Plate
Refinishing a Grand Piano Plate
There are several steps we take when refinishing a vintage piano’s plate. The original finish is first removed and the plate is carefully hand sanded. Removing the original finish is a process that is very labor-intensive and takes a good deal of time. After the plate has been sanded and carefully cleaned, any casting imperfections or other voids are puttied. This creates a smoother surface for the new finish. Once the primer has been applied, lacquer or polyurethane mixed with bronze flake powder is sprayed in multiple coats over the raw piece of cast iron. After the finish has dried, the raised lettering is detailed by one of our artisans. A clear coat of lacquer is then sprayed over the entire plate. This protects the finish and creates the desired level of sheen. For more about our piano restoration methods, click here.