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 savings 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, so don't
breathe in deeply when you have your next holy burning of Beatles or
back-masked devil-worship records. :-) 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.