Styrene (properly, Polystyrene)
Hard, relatively inflexible plastic used to press records, mainly 7-inch singles, mainly using the injection moulding process. The material is heated to a liquid form and is then squirted or injected into the closed stampers in the press. This requires that the labels be either glued or painted on after the record leaves the press. The cost saving to the manufacturer comes from the extended life of the stampers because of the lack of a heating cycle to the stampers. The material can also be reused without noticeable change to its moulding properties. Styrene records will therefore usually have very quiet surfaces when found in an unplayed mint condition, but unfortunately they will wear to a noisy condition rapidly, especially if played with a bad stylus or an improperly tracking tone arm. They also are more prone to cue burn. The Columbia Records Pittman, New Jersey pressing plant was once the major source of injection moulded styrene pressings, and pressings from this plant are found on many small labels. Look for the glued-on labels.
Painted-on labels can be found on records from the Amy / Bell / Mala group.
Vinyl (properly Polyvinyl Chloride).
Relatively flexible material used since the early 1930s to make non-breakable records. Its fumes are an acknowledged carcinogen. Usually pressed by compression moulding, which allows the label to be an integral part of the pressing itself. This process also requires that there be extra material, which spills out the sides of the press, therefore this extra material is routinely ground up and re-used. Because vinyl does not re-heat and re-cool to a smooth, glossy surface, the excessive use of "re-grind" mixed in with virgin vinyl can account for the inherently noisy surface of even unplayed mint examples of the cheap pressings that some record companies used. Noise can be seen and heard by looking at and/or playing the un-grooved surface of the lead-in and lead-out areas. If this area looks or sounds grainy, then the grooves will also have some of this grainy background sound. The stampers used for the compression moulding process will start to break down after only 1,000 pressings because they are forced to expand and contract when heated by steam at the start of the pressing cycle and then cooled to solidify the record. Some companies routinely overused their stampers for their pop record series.
Dynaflex.
Ultra-thin pressings of high-grade virgin vinyl introduced by RCA Victor in late 1969. Although considered crap by most collectors because they do not seem flat when held, they actually have much quieter surfaces then most of the popular records pressed by RCA in the mid-to-late-1960s due to the extraordinarily high percentage of re-grind vinyl used in all but its Red Seal, Vintage Series, and Original Cast pressings. Dynaflex was also less prone to breakage and permanent warpage in shipment. Its lighter weight reduced shipping costs and allowed for the use of a higher grade of vinyl because less material was required. They were supposed to lie flat on the turntable due to their own weight, but RCA forgot that many people had changers with 8-inch turntables! Dynagroove. Record cutting system introduced by RCA Victor in 1962 that supposedly reduced tracking distortion by computer controlling cutting characteristics to overcome the imagined faults of playback equipment. Considered a disaster by everyone except the New York Times writer Hans Fantel who wrote the blurb inserted in all of the early pressings, it brought the golden age of RCA Victor Living Stereo to a screeching halt. Because there is a possibility that this system was used on later re-mastering of the early Living Stereo records, collectors try to obtain only early pressings of these masterpieces--usually called "Shaded Dogs." The words "Stereo-Orthophonic" are on the record label and sometimes the cover of the "good" Living Stereo albums.
Acetate/Lacquer
Is usually a reference cut that is made on ultra high-grade methylcellulose sprayed onto thick aluminum discs. Reference acetates are primarily to make certain the record will sound somewhat like the tape. Often they are also made to allow a club or radio disc jockey to play the music on turntables before it has been pressed as a normal record. Acetate is a misnomer. It is actually a Lacquer.