How Records Were Made
Early discs, 45-rpm records, LPs, and other forms of records such as transcription discs were all made using much the same process. After an original recording was captured on a soft wax "master," electroplating technology was used to make a hard metal stamper, from which multiple copies could be pressed. There were numerous variations, of course.
This series of photos (except for the first one) appears to have been taken in the late 1950s, and shows some of the operations that went into making commercial LP records at that time.
In the studio (this photo is from the late 1940s), original recordings would be made on tape. These originals would be edited to create a master tape. The master tape was the basis of the disc copies made later.
A master tape being used to cut an acetate master disc.
Cutting the acetate disc. The recording engineer peers through a microscope to ensure that the groove does not have serious defects.
The acetate is given a silver coating. By dipping it into a chemical bath through which a small electric current is flowing, dissolved silver is transferred to the surface of the disc, coating even the tiniest details in the groove.
The delicate plating on the acetate disc is built up by giving it additional plating baths to form nickel and copper layers. The plating is stripped away from the acetate, then used to make another heavy metal copy, called the mother. This mother copy is used to make one or more stampers, from which the vinyl discs will be pressed.
A technician lifts the heavy "mother" disc from its plating bath.
Elsewhere in the record pressing plant, a worker pours bags of powdered vinyl plastic into machinery that will heat it and prepare it to be made into records.
A lump or "biscuit" of hot vinyl is placed into the stamper (shown here with its lid open). When the operator closes the stamper, it forces the molten vinyl into the grooves and forms a record. When the vinyl cools, the record is removed from the stamper and excess vinyl is trimmed from the edges.
Workers insert the records into inner sleeves and outer jackets and put them into boxes for shipment.