The lacquer discs which were cut on the previous step, are then passing through the galvanic process to create the metal stampers.
The stampers are essentially a negative image of the original recording that are used to press the grooves into the vinyl.
Firstly, the lacquer disc is cleaned carefully using a washing system with demineralized water and then subjected to a dedicated degreasing bath followed by chemical activation. The lacquer is then “sensitised” in a liquid “dip” preparing the lacquer for “silvering”.
At this phase the lacquer is placed on a slowly rotating vertical turntable and is sprayed with a silver nitrate solution to form a thin layer of conductive silver on its surface.
The lacquer is then rinsed before the next processes start, which involves a three-stage electroforming process:
1. Father (original) production
A bath containing nickel salt and other components is utilized to electroform the silvered lacquer resulting in the formation of a metallic nickel layer over the surface.
This process consists of two steps: first, a lower current is utilized to slowly form an initial layer of nickel coverage on the silver, followed by a stronger current to achieve the necessary thickness.
The separation of the nickel layer from the lacquer produces a negative record referred to as a “father” or an “original.”
Unfortunately, the silvering process damages the grooves on the original lacquer after separation. Therefore, only one father can be produced per lacquer. After the separation, the original lacquer is no longer usable, and the nickel father can be used for creating other production components.
2. Mother (positive) production
The outcome of the subsequent electroforming procedure is referred to as a “positive” or a “mother.” Once the nickel father is cleaned, de-silvered, passivated, and a separating layer is established, it is submerged in another nickel bath that varies in certain parameters from the prior one, to generate a second nickel layer, which is a mirror image of the father.
Once mechanically separated from the father, a copy (positive) of the original recording is produced. The mother, therefore, retains a duplicate of the initial sound grooves which is an exact playable copy of the master lacquer. It’s feasible to generate several mothers from one father.
When the mother is approved, the catalog number is etched into the outlined groove area. This number is the fundamental identification code that helps to determine which plate and label correspond to which side of the record. This number is transferred to the stampers and will be visible on all pressed records.
3. Stamper (matrix) production
Next, the engraved nickel mother is thoroughly washed, degreased, passivated, and a dividing layer is created. The mother is then submerged in a third electroforming bath that contains a solution of nickel salt and other substances, with slightly different parameters than the prior bath to gradually form the necessary metallic nickel layer on the mother’s surface.
Once the acquired nickel layer is separated from the mother, another mirror image (negative) of the record is obtained, resulting in an unformed stamper.
This stamper can then be utilized to press approximately up to 1000 vinyl records. It is possible to create several stampers from one mother in order to achieve higher quantity pressings or reissues after years.
Once the stampers are produced, they need to be shaped and trimmed to fit into the moulds of the pressing machine.
To ensure the quality of the press, the back side of the stamper must be completely flat and smooth, without any imperfections. The stamper is positioned on a unique rotating wheel tool and is manually sanded with varying grades of abrasive sandpaper. This process finely polishes the back surface of the stamper. To avoid damaging the grooved surface, a soft velvet pad is placed on the front side of the stamper during the sanding process.
In order to ensure the highest quality playback, the spiral groove which contains the sound must be precisely centred on the physical centre of the record. To achieve this, it requires an accurate centring of the central hole on the stamper. The stamper is placed in the centre of a rotating wheel. A microscope is used to view a magnified image of the stamper’s grooves on a screen, and the operator manually adjusts the position of the stamper to centre the groove within the tolerance field. Once centred, a machine is used to create the central hole with the required dimensions.
In order to ensure that the stamper fits the required diameter of the final record size, its edges must be trimmed. This is done by securing the stamper onto a trimming machine that utilizes a rotary disc with a cutting blade. The stamper is then cut to the specific dimensions required for the particular format, which can range from 32cm, 26,5cm to 19,2cm. Finally, the sharp edges of the stamper are polished by hand.
A specific device is used to shape the edges of the stamper in order to attain the desired shape of the stamping mould and secure its position during the pressing phase. This shaping process is performed on a press dedicated to this task. After this process, the stamper is ready to be used in the pressing machine for the production of the vinyl records.