The flat record and record player were invented by Emile Berliner in 1888 and then improved upon by Eldridge Johnson in 1890. The two entered a business partnership, calling their company "The Victor Talking Machine Company." Thick and brittle, these earliest flat records were made of some combination of rubber, wax, shellac (a resin from Southeast Asian insects), paper and powdered slate. Because of this inflexible material, the grooves in the records could only hold a few minutes of recording on each side.
In 1931, the RCA Victor company (Berliner and Johnson's expanded business), put out the first vinyl albums, called "long-playing" albums (LPs), which made less surface noise and were more flexible than the old records. The new records were commercially unsuccessful at first, largely due to the popularity of the radio and the low record consumption levels during the Great Depression. Columbia Records made a similar attempt at commercializing vinyl records in 1932 with their "longest-playing" 10-inch records, but this foray ended within a year as Columbia faced the same problems as RCA Victor.
Due to shortages during World War II in America, shellac -- one of the primary materials in non-vinyl records -- had become increasingly uneconomical for record producers to use. Some new discs being sent to soldiers abroad or from record labels to DJs across the country began to be pressed in more durable (and more available) vinyl. In 1948 Columbia Records introduced the vinyl "microgroove" records which could fit two to three times as many grooves-per-square-inch as the old shellac records, allowing them to make records of up to roughly 50 minutes. The new records were bigger than old records -- measuring 12 inches in diameter -- used grooves 1/3 the size of old records and rotated at a slower speed, all contributing to increased playing time. By this point, the 10-inch record had become mostly obsolete, while the 12-inch record became the standard consumer record size; 7-inchers soon became commonly used for artists' singles.
The vinyl quality of records has varied based on the proportions of "virgin," new and recycled vinyl used in the composition of the records. Recycled vinyl comes from old, remelted discs as well as from excess material pushed out during the stamping and pressing process of new discs. The recycled vinyl typically does not resolidify smoothly and thus is a cause of sound imperfections in records. Most records are about 70% virgin vinyl and 30% recycled, though during the 1970s record pressers opted for lighter-weight presses that used lower-quality vinyl. Higher-quality vinyl has a higher concentration of "virgin" vinyl and thus fewer sound-distorting impurities. This also means they weigh more than regular records, and thus are also known as "heavyweight" records. These are usually considered preferable by connoisseurs of vinyl albums. Lightweight vinyl has been primarily used for 7-inch single discs.
Higher-quality records, with a wider range of frequencies to their sound reproduction, were the result of more advanced methods of recording rather than changes in the physical vinyl composition of the records themselves. Such high fidelity ("Hi-Fi") records appeared as early as the 1920s, with two separate channels for lower and higher frequencies used to reproduce the fuller range of sound. These recordings were exclusively monophonic (meaning, if you were to listen with headphones, both sides would emit the exact same sounds), but stereophonic records came into commercial use in 1957. These records read not only horizontal engravings on the records' channels but the vertical ones in the same channel as well. Records' audio quality would continue to improve for the coming decades until cassette tapes and compact discs surpassed records as the primary media of music consumption. However, these changes owed largely to improvements in recording technology and not to changes in the type or composition of the vinyl used in the records.