Le Sony'r Ra, better known as Sun Ra, was an American jazz composer, bandleader and synthesizer player, poet known for his experimental music, "cosmic" philosophy, prolific output, theatrical performances. For much of his career, Ra led "The Arkestra", an ensemble with an ever-changing name and flexible line-up. Born and raised in Alabama, Blount became involved in the Chicago jazz scene during the late 1940s, he soon abandoned. He developed a complex persona and an idiosyncratic, myth-based credo that would make him a pioneer of Afrofuturism, he claimed to be an alien from Saturn on a mission to preach peace, throughout his life he publicly denied ties to his prior identity. His eclectic and avant-garde music echoed the entire history of jazz, from ragtime and early New Orleans hot jazz, to swing music, free jazz and fusion, his compositions ranged from keyboard solos to works for big bands of over 30 musicians, along with electronic excursions, chants, percussion pieces, anthems. From the mid-1950s until his death, Ra led the musical collective The Arkestra.
Its performances included dancers and musicians dressed in elaborate, futuristic costumes inspired by ancient Egyptian attire and the Space Age. Though his mainstream success was limited, Sun Ra was a prolific recording artist and frequent live performer, remained both influential and controversial throughout his life for his music and persona, he is now considered an innovator. Over the course of his career, he recorded dozens of singles and over one hundred full-length albums, comprising well over 1000 songs, making him one of the most prolific recording artists of the 20th century, he was born Herman Blount on May 22, 1914, in Birmingham, Alabama, as discovered by his biographer, John F. Szwed, published in his 1998 book, he was named after the popular vaudeville stage magician Black Herman, who had impressed his mother. He was nicknamed "Sonny" from his childhood, had an older sister and half-brother, was doted upon by his mother and grandmother. For decades little was known about Sun Ra's early life, he contributed to its obscurity.
As a self-invented person, he gave evasive, contradictory or nonsensical answers to personal questions, denied his birth name. He speculated, only half in jest, that he was distantly related to Elijah Poole famous as Elijah Muhammad, leader of the Nation of Islam, his birthday for years remained unknown, as he claimed it for years ranging from 1910 to 1918. Only a few years before his death, the date of Sun Ra's birth was still a mystery. Jim Macnie's notes for Blue Delight said, but Szwed was able to uncover a wealth of information about his early life and confirmed a birth date of May 22, 1914. As a child, Blount was a skilled pianist. By the age of 11 or 12, he was sight reading music. Birmingham was an important stop for touring musicians, he saw famous musicians such as Fletcher Henderson, Duke Ellington, Fats Waller, along with others who were quite talented but never made the big time. Sun Ra once said, "The world let down a lot of good musicians". In his teenage years, Blount demonstrated prodigious musical talent: many times, according to acquaintances, he went to big band performances and produced full transcriptions of the bands' songs from memory.
By his mid-teens, Blount was performing semi-professionally as a solo pianist, or as a member of various ad hoc jazz and R&B groups. He attended Birmingham's segregated Industrial High School, where he studied under music teacher John T. "Fess" Whatley, a demanding disciplinarian, respected and whose classes produced many professional musicians. Though religious, his family was not formally associated with any Christian church or sect. Blount had few or no close friends in high school but was remembered as kind-natured and quiet, an honor roll student, a voracious reader, he took advantage of the Black Masonic Lodge as one of the few places in Birmingham where African Americans had unlimited access to books. Its collection on Freemasonry and other esoteric concepts made a strong impression on him. By his teens, Blount suffered from cryptorchidism, it left him with a nearly constant discomfort. Szwed suggests that Blount felt shame about it and the condition contributed to his isolation. In 1934 Blount was offered his first full-time musical job by Ethel Harper, his biology teacher from the high school, who had organized a band to pursue a career as a singer.
Blount joined a musicians' trade union and toured with Harper's group through the US Southeast and Midwest. When Harper left the group mid-tour to move to New York, Blount took over leadership of the group, renaming it the Sonny Blount Orchestra, they continued touring for several months before dissolving as unprofitable. Though the first edition of the Sonny Blount Orchestra was not financially successful, they earned positive notice from fans and other musicians. Blount afterward found steady employment as a musicia
Edward Kennedy "Duke" Ellington was an American composer and leader of a jazz orchestra, which he led from 1923 until his death over a career spanning more than fifty years. Born in Washington, D. C. Ellington was based in New York City from the mid-1920s onward and gained a national profile through his orchestra's appearances at the Cotton Club in Harlem. In the 1930s, his orchestra toured in Europe. Although considered to have been a pivotal figure in the history of jazz, Ellington embraced the phrase "beyond category" as a liberating principle and referred to his music as part of the more general category of American Music rather than to a musical genre such as jazz; some of the jazz musicians who were members of Ellington's orchestra, such as saxophonist Johnny Hodges, are considered to be among the best players in the idiom. Ellington melded them into the best-known orchestral unit in the history of jazz; some members stayed with the orchestra for several decades. A master at writing miniatures for the three-minute 78 rpm recording format, Ellington wrote more than one thousand compositions.
Ellington recorded songs written by his bandsmen, for example Juan Tizol's "Caravan", "Perdido", which brought a Spanish tinge to big band jazz. In the early 1940s, Ellington began a nearly thirty-year collaboration with composer-arranger-pianist Billy Strayhorn, whom he called his writing and arranging companion. With Strayhorn, he composed many extended compositions, or suites, as well as additional short pieces. Following an appearance at the Newport Jazz Festival, in July 1956, Ellington and his orchestra enjoyed a major revival and embarked on world tours. Ellington recorded for most American record companies of his era, performed in several films, scored several, composed a handful of stage musicals. Ellington was noted for his inventive use of the orchestra, or big band, for his eloquence and charisma, his reputation continued to rise after he died, he was awarded a posthumous Pulitzer Prize Special Award for music in 1999. Ellington was born on April 29, 1899, to James Edward Ellington and Daisy Ellington in Washington, D.
C. Both his parents were pianists. Daisy played parlor songs and James preferred operatic arias, they lived with his maternal grandparents at 2129 Ida Place, NW, in the West End neighborhood of Washington, D. C. Duke's father was born in Lincolnton, North Carolina, on April 15, 1879, moved to Washington, D. C. in 1886 with his parents. Daisy Kennedy was born in Washington, D. C. on January 4, 1879, the daughter of a former American slave. James Ellington made blueprints for the United States Navy; when Ellington was a child, his family showed racial pride and support in their home, as did many other families. African Americans in D. C. worked to protect their children from the era's Jim Crow laws. At the age of seven, Ellington began taking piano lessons from Marietta Clinkscales. Daisy surrounded her son with dignified women to reinforce his manners and teach him to live elegantly. Ellington's childhood friends noticed that his casual, offhand manner, his easy grace, his dapper dress gave him the bearing of a young nobleman, began calling him "Duke."
Ellington credited his friend Edgar McEntree for the nickname. "I think he felt that in order for me to be eligible for his constant companionship, I should have a title. So he called me Duke."Though Ellington took piano lessons, he was more interested in baseball. "President Roosevelt would come by on his horse sometimes, stop and watch us play", he recalled. Ellington went to Armstrong Technical High School in Washington, D. C, he gained his first job selling peanuts at Washington Senators baseball games. In the summer of 1914, while working as a soda jerk at the Poodle Dog Café, Ellington wrote his first composition, "Soda Fountain Rag", he created the piece by ear, as he had not yet learned to write music. "I would play the'Soda Fountain Rag' as a one-step, two-step, waltz and fox trot", Ellington recalled. "Listeners never knew. I was established as having my own repertoire." In his autobiography, Music is my Mistress, Ellington wrote that he missed more lessons than he attended, feeling at the time that playing the piano was not his talent.
Ellington started sneaking into Frank Holiday's Poolroom at the age of fourteen. Hearing the poolroom pianists play ignited Ellington's love for the instrument, he began to take his piano studies seriously. Among the many piano players he listened to were Doc Perry, Lester Dishman, Louis Brown, Turner Layton, Gertie Wells, Clarence Bowser, Sticky Mack, Blind Johnny, Cliff Jackson, Claude Hopkins, Phil Wurd, Caroline Thornton, Luckey Roberts, Eubie Blake, Joe Rochester, Harvey Brooks. Ellington began listening to, imitating ragtime pianists, not only in Washington, D. C. but in Philadelphia and Atlantic City, where he vacationed with his mother during the summer months. He would sometimes hear strange music played by those who could not afford much sheet music, so for variations, they played the sheets upside down. Henry Lee Grant, a Dunbar High School music teacher, gave him private lessons in harmony. With the additional guidance of Washington pianist and band leader Oliver "Doc" Perry, Ellington learned to read sheet music, project a professional style, improve his technique.
Ellington was inspired by his first encounters with stride pianists James P. Johnson and Luckey Roberts. In New York he took advice from Will Marion Cook, Fats Waller, Sidney Bechet. Ellington started to play gigs in cafés and clubs in and aro
The RCA Corporation was a major American electronics company, founded as the Radio Corporation of America in 1919. It was a wholly owned subsidiary of General Electric. An innovative and progressive company, RCA was the dominant electronics and communications firm in the United States for over five decades. RCA was at the forefront of the mushrooming radio industry in the early 1920s, as a major manufacturer of radio receivers, the exclusive manufacturer of the first superheterodyne models. RCA created the first American radio network, the National Broadcasting Company; the company was a pioneer in the introduction and development of television, both black-and-white and color. During this period, RCA was identified with the leadership of David Sarnoff, he was general manager at the company's founding, became president in 1930, remained active, as chairman of the board, until the end of 1969. RCA's impregnable stature began to weaken in the mid-1970s, as it attempted to diversify and expand into a multifaceted conglomerate.
The company suffered enormous financial losses in the mainframe computer industry and other failed projects such as the CED videodisc. In 1986, RCA was reacquired by General Electric, which over the next few years liquidated most of the corporation's assets. Today, RCA exists as a brand name only. RCA originated as a reorganization of the Marconi Wireless Telegraph Company of America. In 1897, the Wireless Telegraph and Signal Company, was founded in London to promote the radio inventions of Guglielmo Marconi; as part of worldwide expansion, in 1899 American Marconi was organized as a subsidiary company, holding the rights to use the Marconi patents in the United States and Cuba. In 1912 it took over the assets of the bankrupt United Wireless Telegraph Company, from that point forward it had been the dominant radio communications company in the United States. With the entry of the United States into World War One in April 1917, the government took over most civilian radio stations, to use them for the war effort.
Although the overall U. S. government plan was to restore civilian ownership of the seized radio stations once the war ended, many Navy officials hoped to retain a monopoly on radio communication after the war. Defying instructions to the contrary, the Navy began purchasing large numbers of stations outright. With the conclusion of the conflict, Congress turned down the Navy's efforts to have peacetime control of the radio industry, instructed the Navy to make plans to return the commercial stations it controlled, including the ones it had improperly purchased, to the original owners. Due to national security considerations, the Navy was concerned about returning the high-powered international stations to American Marconi, since a majority of its stock was in foreign hands, the British largely controlled the international undersea cables; this concern was increased by the announcement in late 1918 of the formation of the Pan-American Wireless Telegraph and Telephone Company, a joint venture between American Marconi and the Federal Telegraph Company, with plans to set up service between the United States and South America.
The Navy had installed a high-powered Alexanderson alternator, built by General Electric, at the American Marconi transmitter site in New Brunswick, New Jersey. It proved to be superior for transatlantic transmissions to the spark transmitters, traditionally used by the Marconi companies. Marconi officials were so impressed by the capabilities of the Alexanderson alternators that they began making preparations to adopt them as their standard transmitters for international communication. A tentative plan made with General Electric proposed that over a two-year period the Marconi companies would purchase most of GE's alternator production. However, this proposal was met with disapproval, on national security grounds, by the U. S. Navy, concerned that this would guarantee British domination of international radio communication; the Navy, claiming it was acting with the support of President Wilson, looked for an alternative that would result in an "all-American" company taking over the American Marconi assets.
In April 1919 two naval officers, Admiral H. G. Bullard and Commander S. C. Hooper, met with GE's president, Owen D. Young, asking that he suspend the pending alternator sales to the Marconi companies; this move would leave General Electric without a buyer for its transmitters, so the officers proposed that GE purchase American Marconi, use the assets to form its own radio communications subsidiary. Young consented to this proposal, effective November 20, 1919, transformed American Marconi into the Radio Corporation of America; the new company was promoted as being a patriotic gesture. RCA's incorporation papers required that its officers needed to be U. S. citizens, with a majority of its stock held by Americans. RCA retained most of the American Marconi staff, although Owen Young became the new company's head as the chairman of the board. Former American Marconi vice president and general manager E. J. Nally become RCA's first president. Nally's term ended on December 31, 1922, he was succeeded the next day by Major General James G. Harbord.
The piano is an acoustic, stringed musical instrument invented in Italy by Bartolomeo Cristofori around the year 1700, in which the strings are struck by hammers. It is played using a keyboard, a row of keys that the performer presses down or strikes with the fingers and thumbs of both hands to cause the hammers to strike the strings; the word piano is a shortened form of pianoforte, the Italian term for the early 1700s versions of the instrument, which in turn derives from gravicembalo col piano e forte and fortepiano. The Italian musical terms piano and forte indicate "soft" and "loud" in this context referring to the variations in volume produced in response to a pianist's touch or pressure on the keys: the greater the velocity of a key press, the greater the force of the hammer hitting the strings, the louder the sound of the note produced and the stronger the attack; the name was created as a contrast to harpsichord, a musical instrument that doesn't allow variation in volume. The first fortepianos in the 1700s had smaller dynamic range.
An acoustic piano has a protective wooden case surrounding the soundboard and metal strings, which are strung under great tension on a heavy metal frame. Pressing one or more keys on the piano's keyboard causes a padded hammer to strike the strings; the hammer rebounds from the strings, the strings continue to vibrate at their resonant frequency. These vibrations are transmitted through a bridge to a soundboard that amplifies by more efficiently coupling the acoustic energy to the air; when the key is released, a damper stops the strings' vibration, ending the sound. Notes can be sustained when the keys are released by the fingers and thumbs, by the use of pedals at the base of the instrument; the sustain pedal enables pianists to play musical passages that would otherwise be impossible, such as sounding a 10-note chord in the lower register and while this chord is being continued with the sustain pedal, shifting both hands to the treble range to play a melody and arpeggios over the top of this sustained chord.
Unlike the pipe organ and harpsichord, two major keyboard instruments used before the piano, the piano allows gradations of volume and tone according to how forcefully a performer presses or strikes the keys. Most modern pianos have a row of 88 black and white keys, 52 white keys for the notes of the C major scale and 36 shorter black keys, which are raised above the white keys, set further back on the keyboard; this means that the piano can play 88 different pitches, going from the deepest bass range to the highest treble. The black keys are for the "accidentals". More some pianos have additional keys. Most notes have three strings, except for the bass; the strings are sounded when keys are pressed or struck, silenced by dampers when the hands are lifted from the keyboard. Although an acoustic piano has strings, it is classified as a percussion instrument rather than as a stringed instrument, because the strings are struck rather than plucked. There are two main types of piano: the upright piano.
The grand piano is used for Classical solos, chamber music, art song, it is used in jazz and pop concerts. The upright piano, more compact, is the most popular type, as it is a better size for use in private homes for domestic music-making and practice. During the 1800s, influenced by the musical trends of the Romantic music era, innovations such as the cast iron frame and aliquot stringing gave grand pianos a more powerful sound, with a longer sustain and richer tone. In the nineteenth century, a family's piano played the same role that a radio or phonograph played in the twentieth century. During the nineteenth century, music publishers produced many musical works in arrangements for piano, so that music lovers could play and hear the popular pieces of the day in their home; the piano is employed in classical, jazz and popular music for solo and ensemble performances and for composing and rehearsals. Although the piano is heavy and thus not portable and is expensive, its musical versatility, the large number of musicians and amateurs trained in playing it, its wide availability in performance venues and rehearsal spaces have made it one of the Western world's most familiar musical instruments.
With technological advances, amplified electric pianos, electronic pianos, digital pianos have been developed. The electric piano became a popular instrument in the 1960s and 1970s genres of jazz fusion, funk music and rock music; the piano was founded on earlier technological innovations in keyboard instruments. Pipe organs have been used since Antiquity, as such, the development of pipe organs enabled instrument builders to learn about creating keyboard mechanisms for sounding pitches; the first string instruments with struck strings were the hammered dul
A musical instrument is an instrument created or adapted to make musical sounds. In principle, any object that produces sound can be considered a musical instrument—it is through purpose that the object becomes a musical instrument; the history of musical instruments dates to the beginnings of human culture. Early musical instruments may have been used for ritual, such as a trumpet to signal success on the hunt, or a drum in a religious ceremony. Cultures developed composition and performance of melodies for entertainment. Musical instruments evolved in step with changing applications; the date and origin of the first device considered. The oldest object that some scholars refer to as a musical instrument, a simple flute, dates back as far as 67,000 years; some consensus dates early flutes to about 37,000 years ago. However, most historians believe that determining a specific time of musical instrument invention is impossible due to the subjectivity of the definition and the relative instability of materials used to make them.
Many early musical instruments were made from animal skins, bone and other non-durable materials. Musical instruments developed independently in many populated regions of the world. However, contact among civilizations caused rapid spread and adaptation of most instruments in places far from their origin. By the Middle Ages, instruments from Mesopotamia were in maritime Southeast Asia, Europeans played instruments from North Africa. Development in the Americas occurred at a slower pace, but cultures of North and South America shared musical instruments. By 1400, musical instrument development was dominated by the Occident. Musical instrument classification is a discipline in its own right, many systems of classification have been used over the years. Instruments can be classified by their material composition, their size, etc.. However, the most common academic method, Hornbostel-Sachs, uses the means by which they produce sound; the academic study of musical instruments is called organology. A musical instrument makes sounds.
Once humans moved from making sounds with their bodies—for example, by clapping—to using objects to create music from sounds, musical instruments were born. Primitive instruments were designed to emulate natural sounds, their purpose was ritual rather than entertainment; the concept of melody and the artistic pursuit of musical composition were unknown to early players of musical instruments. A player sounding a flute to signal the start of a hunt does so without thought of the modern notion of "making music". Musical instruments are constructed in a broad array of styles and shapes, using many different materials. Early musical instruments were made from "found objects" such a shells and plant parts; as instruments evolved, so did the selection and quality of materials. Every material in nature has been used by at least one culture to make musical instruments. One plays a musical instrument by interacting with it in some way—for example, by plucking the strings on a string instrument. Researchers have discovered archaeological evidence of musical instruments in many parts of the world.
Some finds are 67,000 years old, however their status as musical instruments is in dispute. Consensus solidifies about artifacts dated back to around 37,000 years old and later. Only artifacts made from durable materials or using durable methods tend to survive; as such, the specimens found. In July 1995, Slovenian archaeologist Ivan Turk discovered a bone carving in the northwest region of Slovenia; the carving, named the Divje Babe Flute, features four holes that Canadian musicologist Bob Fink determined could have been used to play four notes of a diatonic scale. Researchers estimate the flute's age at between 43,400 and 67,000 years, making it the oldest known musical instrument and the only musical instrument associated with the Neanderthal culture. However, some archaeologists and ethnomusicologists dispute the flute's status as a musical instrument. German archaeologists have found mammoth bone and swan bone flutes dating back to 30,000 to 37,000 years old in the Swabian Alps; the flutes were made in the Upper Paleolithic age, are more accepted as being the oldest known musical instruments.
Archaeological evidence of musical instruments was discovered in excavations at the Royal Cemetery in the Sumerian city of Ur. These instruments, one of the first ensembles of instruments yet discovered, include nine lyres, two harps, a silver double flute and cymbals. A set of reed-sounded silver pipes discovered in Ur was the predecessor of modern bagpipes; the cylindrical pipes feature three side-holes. These excavations, carried out by Leonard Woolley in the 1920s, uncovered non-degradable fragments of instruments and the voids left by the degraded segments that, have been used to reconstruct them; the graves these instruments were buried in have been carbon dated to between 2600 and 2500 BC, providing evidence that these instruments were used in Sumeria by this time. Archaeologists in the Jiahu site of central Henan province of China have found flutes made of bones that date back 7,000 to 9,000 years, representing some of the "earliest complete, tightly-dated, multinote musical instruments" found.
Scholars agree that there are no reliable methods of determining the exact chronology of musical instruments across cultures. Comparing and organizing instruments based on their complexity is misleading, since advancements in musical instruments have sometimes reduced complexity. For example, construction of early slit drums involved f
A musical keyboard is the set of adjacent depressible levers or keys on a musical instrument. Keyboards contain keys for playing the twelve notes of the Western musical scale, with a combination of larger, longer keys and smaller, shorter keys that repeats at the interval of an octave. Depressing a key on the keyboard makes the instrument produce sounds—either by mechanically striking a string or tine, plucking a string, causing air to flow through a pipe organ, striking a bell, or, on electric and electronic keyboards, completing a circuit. Since the most encountered keyboard instrument is the piano, the keyboard layout is referred to as the piano keyboard; the twelve notes of the Western musical scale are laid out with the lowest note on the left. Because these keys were traditionally covered in ivory they are called the white notes or white keys; the keys for the remaining five notes—which are not part of the C major scale— are raised and shorter. Because these keys receive less wear, they are made of black colored wood and called the black notes or black keys.
The pattern repeats at the interval of an octave. The arrangement of longer keys for C major with intervening, shorter keys for the intermediate semitones dates to the 15th century. Many keyboard instruments dating from before the nineteenth century, such as harpsichords and pipe organs, have a keyboard with the colours of the keys reversed: the white notes are made of ebony and the black notes are covered with softer white bone. A few electric and electronic instruments from the 1960s and subsequent decades have done this; some 1960s electronic organs used reverse colors or gray sharps or naturals to indicate the lower part of a single keyboard divided into two parts, each controlling a different registration or sound. Such keyboards accommodate melody and contrasting accompaniment without the expense of a second manual, were a regular feature in Spanish and some English organs of the renaissance and baroque eras; the break was between middle C and C-sharp, or outside of Iberia between B and C.
Broken keyboards reappeared in 1842 with the harmonium, the split occurring at E4/F4. The reverse-colored keys on Hammond organs such as the B3, C3 and A100 are latch-style radio buttons for selecting pre-set sounds; the chromatic range of keyboard instruments has tended to increase. Harpsichords extended over five octaves in the 18th century, while most pianos manufactured since about 1870 have 88 keys; some modern pianos have more notes. While modern synthesizer keyboards have either 61, 76 or 88 keys, small MIDI controllers are available with 25 notes. Organs have 61 keys per manual, though some spinet models have 44 or 49. An organ pedalboard is a keyboard with long pedals played by the organist's feet. Pedalboards vary in size from 12 to 32 notes. In a typical keyboard layout, black note keys have uniform width, white note keys have uniform width and uniform spacing at the front of the keyboard. In the larger gaps between the black keys, the width of the natural notes C, D and E differ from the width of keys F, G, A and B.
This allows close to uniform spacing of 12 keys per octave while maintaining uniformity of seven "natural" keys per octave. Over the last three hundred years, the octave span distance found on historical keyboard instruments has ranged from as little as 125 mm to as much as 170 mm. Modern piano keyboards ordinarily have an octave span of 164–165 mm. Several reduced-size standards have been marketed. A 15/16 size and the 7/8 DS Standard keyboard developed by Christopher Donison in the 1970s and developed and marketed by Steinbuhler & Company. U. S. pianist Hannah Reimann has promoted piano keyboards with narrower octave spans and has a U. S. patent on the apparatus and methods for modifying existing pianos to provide interchangeable keyboards of different sizes. There have been variations in the design of the keyboard to address musical issues; the earliest designs of keyboards were based on the notes used in Gregorian chant and as such would include B♭ and B♮ both as diatonic "white notes," with the B♮ at the leftmost side of the keyboard and the B♭ at the rightmost.
Thus, an octave would have eight "white keys" and only four "black keys." The emphasis on these eight notes would continue for a few centuries after the "seven and five" system was adopted, in the form of the short octave: the eight aforementioned notes were arranged at the leftmost side of the keyboard, compressed in the keys between E and C. During the sixteenth century, when instruments were tuned in meantone temperament, some harpsichords were constructed with the G♯ and E♭ keys split into two. One portion of the G♯ key operated a string tuned to G♯ and the other operated a string tuned to A♭
Silicone rubber is an elastomer composed of silicone—itself a polymer—containing silicon together with carbon and oxygen. Silicone rubbers are used in industry, there are multiple formulations. Silicone rubbers are one- or two-part polymers, may contain fillers to improve properties or reduce cost. Silicone rubber is non-reactive and resistant to extreme environments and temperatures from -67 °F to 572 °F while still maintaining its useful properties. Due to these properties and its ease of manufacturing and shaping, silicone rubber can be found in a wide variety of products, including: voltage line insulators, automotive applications. In its uncured state, silicone rubber is a highly-adhesive gel or liquid. In order to convert to a solid, it must be vulcanized, or catalyzed; this is carried out in a two-stage process at the point of manufacture into the desired shape, in a prolonged post-cure process. It can be injection molded. Silicone rubber may be cured by a platinum-catalyzed cure system, a condensation cure system, a peroxide cure system, or an oxime cure system.
For the platinum-catalyzed cure system, the curing process can be accelerated by adding heat or pressure. In a platinum-based silicone cure system called an addition system, two different chemical groups react in the presence of platinum. In this reaction, an ethyl group is formed and there are no byproducts. Two separate components must be mixed to catalyze the polymers: one component contains a platinum complex which must be mixed with the second component, a hydride- and a vinyl-functional siloxane polymer, creating an ethyl bridge between the two; such silicone rubbers cure though the rate of or ability to cure is inhibited in the presence of elemental tin and many amine compounds. Condensation curing systems can be two-part systems. In one-part or RTV system, a cross-linker exposed to ambient humidity experiences a hydrolysis step and is left with a hydroxyl or silanol group; the silanol condenses further with another hydrolyzable group on the polymer or cross-linker and continues until the system is cured.
Such a system will cure on its own at room temperature and is not inhibited by contact with other chemicals, though the process may be affected by contact with some plastics or metals and may not take place at all if placed in contact with already-cured silicone compounds. The crosslinkers used in condensation cure systems are alkoxy, ester, enoxy or oxime silanes such as methyl trimethoxy silane for alkoxy-curing systems and methyl triacetoxysilane for acetoxy-curing systems. In many cases an additional condensation catalyst is added to cure the RTV system and achieve a tack-free surface. Organotitanate catalysts such as tetraalkoxy titanates or chelated titanates are used in alkoxy-cured systems. Tin catalysts such as dibutyl tin dilaurate can be used in acetoxy-cured systems. Acetoxy tin condensation is one of the oldest cure chemistries used for curing silicone rubber, is the one used in household bathroom caulk. Depending on the type of detached molecule, it is possible to classify silicone systems as acidic, neutral or alkaline.
Two-part condensation systems package the cross-linker and condensation catalyst together in one part while the polymer and any fillers or pigments are in the second part. Mixing of the two parts causes the curing to take place. Once cured, condensation systems are effective as sealants and caulks in plumbing and building construction and as molds for casting polyurethane and polyester resins, waxes and low-melting-temperature metals such as lead, they are very flexible and have a high tear strength. They do not require the use of a release agent. Peroxide curing is used for curing silicone rubber; the curing process leaves behind byproducts, which can be an issue in food contact and medical applications. However, these products are treated in a postcure oven which reduces the peroxide breakdown product content. One of the two main organic peroxides used, dicumyl peroxide, has principal breakdown products of acetophenone and phenyl-2-propanol; the other is dichlorobenzoyl peroxide, whose principal breakdown products are dichlorobenzoic acid and dichlorobenzene.
The first silicone elastomers were developed in the search for better insulating materials for electric motors and generators. Resin-impregnated glass fibers were the state-of-the-art materials at the time; the glass was heat resistant, but the phenolic resins would not withstand the higher temperatures that were being encountered in new smaller electric motors. Chemists at Corning Glass and General Electric were investigating heat-resistant materials for use as resinous binders when they synthesized the first silicone polymers, demonstrated that they worked well and found a route to produce it commercially; the term "silicone" is a misnomer. The suffix -one is used by chemists to denote a substance with a double-bonded atom of oxygen in its backbone; when first discovered, silicone was erroneously believed to have oxygen atoms bonded in this way. Technically correct term for the various si