Session Notes 7 - The Vinyl Frontier (Part 4 Lacquers & Pressings)
Updated: Apr 6, 2021
This month I’m looking at the cutting and pressing process. After all the hardwork of recording, mixing and mastering we get to the “real deal” stage of actually cutting a groove into something. That something is called a lacquer. It’s also known as an acetate but this is a misnomer given that no acetate is involved anymore. The lacquer is an aluminium disc coated in black nitrocellulose lacquer. The coating is very soft and can be damaged easily.
They come in three different sizes: 10” for 7” singles, 12” for 10” records and 14” for a 12” album. The reason for the lacquer’s larger size is that there is about an inch of handling area around the edge.
The process usually begins with a check on the audio source to determine levels and EQ and then the cut can begin. The lathe will cut a ‘run-in’ groove and then the audio playback will begin. The groove is cut in one continuous path all the way to the end of the program material and then the run-out groove which ends in a ‘locked loop’. This is to stop the stylus wandering onto the label area which will cause stylus damage. When an album consists of individual songs a special silent transmission groove is cut between the tracks. This gives you the familiar gaps between the tracks. The very impressive technical name for this is the VTM or Visual Track Marker.
At the end of your cut a new lacquer disc is required for side B. You don’t turn the lacquer over as you would a finished record. At the end of this process the engineer will use a metal scribe to write information in between the run-out grooves. This will usually be the catalogue number for the label and the side designation for A or B. Other “secret” messages can also be written. One famous vinyl mastering engineer named George Peckham used to inscribe “A Porky Prime Cut” between the run-out groove of nearly every record he cut.
There is one other technique for vinyl mastering which is known as DMM (Direct Metal Mastering). The groove is cut to a copper plated disc instead of a lacquer. This method has dwindled in popularity despite its more accurate grooves because people found the resulting sound too harsh and edgy. It is still available if you want it but the sound from the lacquer is still the preferred option.
The lacquer(s) are sent to the manufacturers where an intriguing process begins. First the lacquers are checked for the slightest speck of dust or dirt. This is absolutely essential. It is then sprayed with silver nitrate and placed in an ‘electroforming bath’. The electrolyte gradually forms a layer of nickel on the surface of the lacquer. When it is ready the nickel layer is peeled away from the lacquer and you have a “negative”, i.e. you have mountains instead of grooves. This is called a Father. The (negative-Father) nickel is then electroplated again to produce a Mother(grooves again). After final inspection it is yet again electroplated and when peeled off of the Mother (sorry about this terminology) it is called a stamper (mountains again). And you can probably guess what that is used for.
Pressings can now begin. The vinyl material is heated to about 160°C which doesn’t melt it completely. A patty of vinyl (also known as a biscuit) is placed onto the mould and the press exerts about 150 tons of pressure as the record is pressed. The labels are also pressed on at the same time. The record is trimmed and cooled with cold water.
Vinyl records come in a variety of weights. The most popular at the moment is 180 grams. Earlier records from the 70s and 80s were typically 120-140 grams. 180 gram vinyl is considered audiophile grade. I don’t know why seeing as the groove depth is the same pretty much on all formats. I mastered a 7” single a good few years back for an Oxford band called Moonkat. They produced a 220 gram record. It was virtually unbendable.
Next month I’ll look at “speciality” options to conclude the vinyl story.