[78-L] Glass Compound 78s

[Michael Biel]

From: "simmonssomer" <simmonssomer at comcast.net>
> I believe that many of the RCA Victor Glenn Miller LP albums of
> pre WW II Chesterfield show line checks were derived from Miller's
> personal stash of glass based discs that had been stored, one upon
> the other, in a pile located in his offices. Many cracked, many not.
> Al Simmons

Most probably only the final few months were glass, if even that many. 
These liner notes were not written by experts, and to them if some were
glass all were glass.  It also makes a better story of their heroics in
saving these if they say the discs were glass instead of a mixture of
glass and aluminum. 

And by the way, just because this thread has remained "Glass Compound
78s" does not mean that this is what they are called.  This is a made-up
name that should never be heard from again. 

Mike Biel  mbiel at mbiel.com  

----- Original Message ----- 
From: "David Lennick" <dlennick at sympatico.ca>
To: "78-L Mail List" <78-l at klickitat.78online.com>
Sent: Tuesday, June 16, 2009 10:22 AM
Subject: Re: [78-L] Glass Compound 78s


> Michael Biel wrote:
>>
>> As dl mentioned, professional grade discs were not marked on the discs
>> themselves, only on the sleeves which often can get switched so that a
>> glass base sleeve could house an aluminum disc, but most home-grade
>> glass base discs are marked on the manufacturer's label. But glass was
>> rarely sold to the home recording market. They used steel base and
>> fibre base discs. Many radio and recording studio labels did mark the
>> discs as glass, but not always because the labels were sometimes
>> prepared by a secretary, not the recording engineer. The first glass
>> Presto discs were very thick and had a metal grommet in the center hole.
>> AudioDevices' AudioDisc brand had a fibre-center that was about
>> 2-inches in diameter, and the edge of how this fits into the larger
>> glass hole can sometimes be seen or felt. Later in the war Presto had a
>> printed label that said glass base, but I am not sure if the discs were
>> shipped with this label on them or if it was to be applied by the user.
>>
>> As to whether glass discs were more flexible when new, I doubt that
>> because one of the reasons glass was used was because it was less
>> flexible than aluminum. One of the selling points of glass prior to the
>> war was that it was ideal for use for mastering because it remains
>> flatter than metal when being electroplated. The first glass discs were
>> shipped in early April 1941, prior to our entry into the war, and before
>> aluminum rationing.
>>
>
> I didn't know that glass discs preceded Pearl Harbor in the US, but they 
> were
> definitely in use in Canada prior to that date..the CBC has many such from
> 1940. Heavy, but not the super thick ones with the grommet .. man, those 
> things
> must weigh five pounds. Even the twelve-inch ones (of which I have two, 
> from
> 1942) are hefty. And prone to cracking.
>
> It should also be noted that studios often didn't attach labels to discs 
> at
> all, but wrote the info in grease pencil or scratched it into the label 
> area.
>
> dl
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