The second step towards the disc
Mastering itself can be divided into two processes: preparation of glass and electroplate processing. In the process of glass preparation itself, we can differentiate glass mastering, optical verification and glass testing. However, electroplate processing consists of electroplate processing itself, which means the creation of a master template, and the process of cleaning the master template surface and the mechanical processing of the master template.
One of the most important stages, not only of mastering, but also of the whole process of pressing and its final effect is the creation of the master template on a so-called glass master (a glass plate), popularly known as glass mastering. Its creation means covering glue with light-sensitive liquid emulsion, which is placed and dried on glass. After drying it again, in this case emulsion, the information which is supposed to be contained on the future disc is illuminated with the light of a laser. The illuminated emulsion is developed. After the cleaning of the light-sensitive substance on the glass master there is left only the illuminated layer of emulsion with the data in the shape of a spiral. In order to solidify the remaining layer or emulsion before metallization, the glass is dried in a special place. On such a prepared glass master a thin layer of silver is put, in order to prepare it for the electrolysation process (the creation of the layer which can conduct the electrical current). In the future, this metal will be replaced by a mixture of the valuable elements Vanadium and Nickel, which, thanks to their properties, allow the reflection of data in a more detailed way.
The next stage in the mastering process includes tests. The glass master for the CD is verified based on the value and parameters, and in the case of glass for DVD is checked on thin glass specially intended for it. At the mastering stage, GM Records ensures the high quality of its services. We care that our client is happy with the final product, and in this case with the data which is reflected in a detailed way.
If, in the currently pre-existing stages of the mastering process, no errors have been found and the test results were successful, the glass master is subject to electroplate processing, which lasts for about one hour. During electroplate processing, a 0.3mm thick layer of nickel is placed on the surface of the glass, in which the recording track of the laser is reflected. The glass master template is removed from the nickel master template which was created, on which, in the later stages of pressing mediums, the discs are replicated.
We can create up to ten master templates from this master template in the “family” process. However, before the appropriate pressing of optical mediums is performed, the nickel master template is cleaned. In the first stage it is soaked in sodium hydroxide, through which the current passes. At this stage, the passivation of silver occurs, which means it blackens.
Next, a solution of ammonia, sodium hydroxide and perhydrol 30% (oxidised water) and deionised water (nuclear – used in nuclear power stations as coolant rods) is poured over the master template. As a result of this process, the master template is cleaned of basic materials – silver, remaining glue and light-sensitive emulsion. However, the final stage of cleaning is the anode passivation, during which all other remaining elements are removed.
The master template created is verified on an optical basis, the data surface is lacquered and then is mechanically processed. In order to obtain an ideal surface to stick to the form of the injection moulding machine for replication, the master is polished. It is also centralised and cut into the expected shape, in most cases a circle.
The master template which is ready for replication is pure nickel, which is tough and shows a great immunity to temperature. The lifespan of one master template for CDs is between 80 thousand units or more, however for DVDs, one master template can be used to press up to 40 thousand mediums and more.