Retrotechtacular: Wax On, Wax Off: How Records Are Made

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In this 1942 tour of the RCA Victor plant in Camden, NJ, we see the complete record making process from the master cut production to the shipping of multiple 78RPM shellac pressings. The film centers around a recording of Strauss’ Blue Danube waltz as performed by the 1940s equivalent of studio musicians, the Victor Salon Orchestra.

The master record starts life as a thin layer of molten wax poured on to a hot circular plate in a dust-free room.  Bubbles and impurities are blow torched out, and the wax is left to cool under a steel dome. This perfect disc is carefully passed to the recording studio through a special slot, where it is laid carefully beneath the cutting stylus.

Unlike today’s multi-track recording sessions, the master was cut from the performance of a complete band or orchestra all playing as they would in concert. The sound engineer was responsible for making fast changes on the fly to ensure sonic  and groove width consistency. 

After cutting, the delicate wax undergoes several phases of electrolysis that form the metal master. It is bombarded first with pure gold and then twice with copper sulfate to build a sturdy disc. The copper ionization process also ensures high fidelity in the final product.

Although mighty, this master won’t last long enough to make all the necessary pressings, so a mother matrix is made. This is a negative image of the master. The mother is formed by electrolytically bathing the master in nickel, and then adding a thin film of some indeterminate substance. Another copper bath, and mother emerges. As soon as possible, the master is separated and whisked away to the storage vault.

Since a positive image is needed for pressing, a stamping matrix is made. Mother gets a nickel bath for durability, and then a copper bath to form the stamping matrix. Many stampers are created so that several records can be pressed at once. These images get a chromium plating to help them last through many pressings.

The stampers are soldered to a rigid backing before getting their very precisely placed spindle hole drilled. This hole is centered by machine and checked through magnification of the grooves as the disc spins. Stampers are washed one last time to remove dust and given a final brushing off and polishing.

These 78RPM records were made from the finest shellac from India, resin from the East Indies, and 18 other secret herbs and spices that are all heated and combined in a 3-story Banbury mixer. The resulting dough is rolled out into a sheet and cut into biscuits, which are square pieces slightly bigger than the final record.

The biscuits are reheated on steam tables right before they are pressed.  Label application is part of the pressing process, and both sides are pressed simultaneously. After this, the ragged edge is smoothed, and each record is tested by human ears. Finally, it is polished, sleeved, counted, boxed, and ready to be shipped to Woolworth’s, Wanamaker’s, or wherever.

A few years after this film was made, the shift to 33RPM vinyl records began. The process really hasn’t changed much over the years. The master, the mother matrix, and the stamping matrix bathe in different chemicals now, and the end result is pressed into a vinyl biscuit rather than shellac.

[Thanks Mlseim]

Retrotechtacular is a weekly column featuring hacks, technology, and kitsch from ages of yore. Help keep it fresh by sending in your ideas for future installments.

 

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