Record Sizes, Speeds, and Materials

78 rpm Record, 10 inch INTRODUCTION:
A discussion of record sizes, speeds and materials could go on forever! Particularly in the early days of recorded music, there were long periods of experimentation with all aspects of vinyl record technology. Eventually, the vinyl record "evolved" into the sizes, speeds, and materials used today. Listed below are some of the highlights of this evolution.

33-1/3 rpm Record, 12 inch SIZES:
Though historically three standard sizes have been used most often (7, 10, and 12 inch), any size is theoretically possible. Most record plants are capable of making record sizes between 5 inches and 12 inches. During the late 1940's, radio shows were often recorded on to 16 inch 33-1/3rpm records so that a complete show could be placed on each side! According to the Guinness Book Of World Records, the smallest commercially produced vinyl record was 2-1/2 inches in diameter and contained a reading of "The Lord's Prayer".

The first widely available record size was the 10 inch record, made of a very thick layer of shellac and dating back to the early 1900's. When greater capacity was needed, record companies produced the 12 inch record. Wide availability of 12 inch records dates back to the late 1940's. It was also at that time, that the connection between music and commercial radio began to take off. This connection brought about the need for small cheap records that could contain the hits of the day. The result of this need was the 7" record, which was designed to be a cheaper, disposable record for the sale of hit songs.

45 rpm Record, 7 inch SPEEDS:
Early 10 inch records were 78rpm. This very fast revolution speed resulted in records being able to hold, at most, a couple of songs on each side. This low capacity brought about the creation of record "albums". These albums were actually what their name suggests... bound "books" or folders which contained sleeves for a group of 78's.

The problem with these early "albums" was their expense, weight, and bulk! During the late 40's, an effort to squeeze more music on each record resulted in the slower spinning 16-2/3rpm (uncommon today), 33-1/3rpm and 45rpm records. These thinner, lighter records could, in many cases, hold and entire "album" worth of music on a single disc. To play music at these slower speeds required new "low mass" record needles. These needles reproduced sounds much more accurately, and with less damage to the record, than the earlier steel needles.

Audio CD, 5 inch MATERIALS: The first true disc shaped records were made of a very thick, brittle Shellac like material. Some of these older records were 3 to 4 times thicker that modern vinyl! This increased thickness and hardness was necessary due to the extreme pressure steel needles and their massive heads would place on a record. Once lighter diamond tip needles were developed with their much improved sound reproduction, vinyl became the material of choice in record manufacturing. The basic materials and processes for vinyl record production have not changed substantially since the 1940's.

Today, vinyl has remained the mainstay of record production. Besides the occasional flexi-disc made of plastic, not much has changed. The only unique developments have been the use of colored vinyls, marbled vinyls, and clear vinyls (particularly for picture discs). Special products such as "virgin", "audiophile", and "1/2 sped master" vinyl while popular in the 70's and 80's, have met with limited success in recent years with the advent of CD audio.