Posted on

Explanation of how vinyl records are made/pressed

-After a long answer to a customer, we decided to post part of it separately as a good explanation how records are made. -Webmaster

When a vinyl record is created there are various “additives” or adjunct liquids which are added to the “charge” of vinyl pellets (that will be melted and subsequently flow into the molding cavity as the press is being closed).  The vinyl pellets are introduced via a chute into a heated auger chamber wherein the vinyl is melted and formed into a biscuit sized puck that will be placed into the center of the record press.  At the same time that the pellets are fed into the auger at least two other liquid compounds are added to the pellets.  The first is an internal “lubricant”, added so the the vinyl will flow smoothly and continuously from the center of the press toward the outside edge of the press.  At the same time another compound is added so that the finished work piece (the record) will separate cleanly from the faces of the stamper molds.  Depending upon the vinyl, these compounds may be mixed ahead of time and are part of the “charge”.  Other times the press operator is adding smaller amounts depending on operating dynamics.  So both an “internal lubricant” and a “mold release agent” are added to the vinyl (usually) during the pressing run.  The operator is usually in charge of several presses during a run and will be moving constantly from press to press adding more or less of the additives depending on press operations and vinyl quality.  Years ago, I visited a pressing plant (no longer in business) where the operator sprayed a proprietary mold release coating on the faces of the press just before the press closed.  If the operator wasn’t not sufficiently fleet of foot, a press would close and clamp shut before he could spray, with (sometimes) disastrous results.

The clamping pressure holding the press closed during the process is very high (40,000 to 70,000 pounds per square inch).  At the completion of the operation, the press is cooled, then opened and the operator removes the record which is then placed on a spindle while further cooling.  Later on, the spindle with many records on will be taken into the packaging room where each record is removed and visually examined for defects.  If no defects are found, the record is slipped into an inner sleeve and then placed into its final outer jacket (or box if a box set).  At NO time in the inspection/packaging operation is the record cleaned or any pressing residues removed from the surface.  Another factor is the following – because the pressure is so high inside the press, the press faces are cooled by forcing cold water through the passages that held very hot steam under high pressure during the pressing operation.  This is to cool the work piece (record) so that it is not in a still molten state when the press opens.  However, this means some of the mold release agent and internal lubricants are locked into the vinyl under high pressure.  Over a period of time, these residues will diffuse from the inside of the record out to the surface creating noise and a gray, powdery contamination that keeps repeating itself.

There are few remaining record pressing plants.  LAST All Purpose Record Cleaner is designed for general purpose record cleaning with the safe, effective removal of dust, air-borne debris, finger-prints, and contamination that might be picked up from the surface of the turntable or table mat.  However, it is not suited to the removal of pressing residues or tenacious oils, fats, or silicon fluids, such as come from the previously discussed release agents and lubricants.  For this you may have success with a Vacuum Record Cleaning Machine such as a Keith Monks (UK), Nitty Gritty or VPI (US).

At The LAST Factory, we manufacture a specialized cleaner called Power Cleaner for Records.  It is specifically formulated to allow deep cleaning and removal of those offending contaminants from the surface of vinyl records.

-Walter Davies