Also the most technically complicated musical instrument, the piano has over 2,500 parts. Several of those parts require thermal processing to produce them or to make them better. We will look at a few of these, including the cast iron plate and the strings. Before doing that, however, let’s consider the history of the instrument.

It may come as no surprise that the piano had its roots in the harpsichord, which grew out of early stringed instruments such as the ancient harp. The harp was mentioned in the book of Genesis. From the harp grew the psaltery, which was an ancient box-type instrument with strings that were plucked with a pick. Although keys were added to make the harpsichord family of instruments, the strings were still plucked. Composers and musicians alike complained that it was “impossible to swell out or diminish the volume of its sound.”

This nuanced weakness led harpsichord manufacturer Bartolomeo de Francesco Cristofori of Padua, Italy, to invent the pianoforte in 1700. This new instrument had hammers that struck the strings by falling under their own weight. Unlike the harpsichord, this new system allowed the strings to continue to vibrate and make sound, with the hammers having the ability to strike the strings loudly or softly. 

The pianoforte used two strings per note compared to today’s pianos that use one string for the lower notes and two or three strings for the middle and higher notes. The Cristofori instrument used four and a half octaves versus today’s pianos with seven and a quarter octaves. The popularity of the pianoforte increased when Frederick the Great purchased several. Johann Sebastian Bach approved of it in 1747.

Piano building began in America in 1775. The process of continuous improvement proceeded throughout the 18th and 19th centuries. One of these improvements was the cast-iron plate for structural strength and cross-stringing of the bass strings over the trebles. John Hawkins, of Philadelphia, was the first to use an iron frame in 1800. He was also a leading developer of the upright piano. By 1870, the “over-strung scale” method was perfected by Steinway & Sons, allowing the strings to cross close to the center of the soundboard where the best sound is produced. 

The quality control of the cast-iron plate is very important. The character of the sand used in the casting process is modified with binders such as clays and coal dust to produce the ideal composition. Metallurgists check the chemical analysis of the iron and monitor the critical temperatures of the process – 2750˚F for molten iron. Recently, vacuum casting has been used to produce cast-iron plates with smooth finishes requiring no grinding. 

By 1911, there were 301 piano builders in the U.S., but the Great Depression resulted in a rapid decline in the production of pianos. There are approximately 15 producers remaining today, but Japan is now the world’s largest producer of pianos. 

Strings are another piano component requiring precision manufacturing and the use of thermal processing. Specialized mills produce the wire from tempered high-carbon steel in diameters as small as 0.006 inch to 0.192 inch. Up to 17 different diameters of wire may be used for the 220 to 240 strings on a single piano. String lengths and diameters increase from treble to bass. Different-length strings of the same diameter can produce different pitches. To attain the slower vibrations needed for the bass notes, strings are wound with other wire, typically copper in today’s pianos. The lowest string is about a ¼ inch in diameter due to the heavier core wire and its winding. Without the winding, bass strings would need to be 30 feet long to produce the necessary sound. Consider that this tough, high-tensile, polished wire is placed under high tension, subjected to repeated blows and bending, and stretched and slackened during tuning … and it is expected to last for decades in service.

Although the traditional piano is manufactured much as it has been for a century, current and future improvements promise to be the result of perfecting the sound via developments in the quality of the cast-iron plate and the string technology. Now you know how thermal processing continues to help make music beautiful. IH

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