How were Diamond Discs Made ?

[Marc Hildebrant]

Group,

Is there a good resource that describes the manufacturing process Edison used for his Diamond Discs ? Maybe something from the Edison National Park ?

Marc

[52089]

I think there's some description in Frow's Edison Disc Phonograph book, and there's more in the Collector's Guide.

[donniej]

There are bits and pieces online but here's the general way it went.

The musicians recorded the requisite "3 good takes". Regardless of whether the recording was acoustic or electric, they were cut to a master blank which (I believe) was a sort of brown wax but with a high percentage of refined montan wax.
In the early years, the wax blank was "gold molded" (sputter coated) and then plated with either copper or nickel. In 1923 (IIRC) the gold molding was abandoned (to speed up production) and the wax blank was powdered with graphite. The first metal part to be produced was a copper negative, it is believed that only this first metal "master" was copper, the rest would be nickel.
Please note that in the Edison vocabulary, a negative was called a "mold" and a positive was called a "record".

An electrotype process was used to plate the negative and generate a positive, this positive was then used to create another generation (or two) from which stampers were made. After the latter generations of metal parts were made, the original copper "master mold" was plated (electrotyped) with nickel and then sealed shut via electroplating. The sealed pair were put into storage as some sort of master-pair. Somewhere along the line (also 1923, IIRC) they decided to always issue all three takes (generally speaking).

I could speculate on the later steps, but I don't have solid info on the production of the discs.