Acetates / Lacquers
Producing an acetate record or more accurately a lacquer coated disc.
The acetate is an intermediate stage prior to the production of the master disc and is used for test purposes to assess the sound transfer from the master tapes to vinyl. If a sound or mix is rejected then the acetate pressed has the potential to be a unique item as there are never many copies of acetates produced.
The acetate is usually an aluminium disc that is covered in a thin coating of nitrocellulose lacquer that has the sound groove, from the master tape, cut into it using a "lathe".
They come in various sizes including 7", 10", 12" and 14"
The cutting head on the lathe, which is like a record player needle but in reverse. The sound is passed through the sapphire cutting stylus which etches the soft lacquer, by moving up and down, left and right, tracing out an exact waveform representation of the music. There is also a small vacuum cleaner beside the cutter to pick up the excess lacquer.
The lacquer is soft and thin and repeated playing of the acetate will degredate the sound. They are manufactured for one purpose and that is for quality control and not repeated playing.
Next is the plating and pressing processes.
At the pressing plant, stampers (or plates) have to be created from the acetates.
Each acetate is coated with a thin layer of silver nitrate and washed in stannous chloride which is then electro-plated with nickel. Once this has set the two are separated and the plate produced will be a negative of the acetate with ridges instead of grooves.
This plate is called the "father plate" or the "master plate", which is then oxidised, plated again and when set the two discs are separated, this time producing a "mother plate". The "mother plate" is an exact replica of the lacquer acetate that was originally brought into the plant and is used to check for any errors in the plating process.
From this "mother plate" further "father plates" are created using the above process and these plates are known as the stamper plates as they are the ones that press the actual records out.
This lengthy process is gone through as the stamper plates wear out after so many pressings and with having a metal "mother plate" on the shelf this enables as many "father plates" to be pressed as required.