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From: Roger Kulp <[log in to unmask]>
> Is that the main cause for lacquer oxidation? I have found a lot
> of Audiodisc lacquers,from the 30s and 40s,that are unplayable
> because of oxidation.   Roger

No, George is talking about the oxidation of the zinc metal, and you do
not have zinc-base discs.  What you are probably seeing is not
oxidation, but is the leaching of palmetic acid or castor oil out of the
lacquer coating.  And are you using Audiodisc as a generic name or a
brand name?  In other words, do you only have this problem on AudioDiscs
made by AudioDevices, or on other brands as well?

Mike Biel  [log in to unmask]  


________________________________
 From: George Brock-Nannestad <[log in to unmask]>
From: Patent Tactics, George Brock-Nannestad
>> Hello,
>> it was, at least in Europe, and frequently the result is horrible today: the
oxidation of zinc under a lacquer layer might appear worse than that of
iron,
because it was more even, and adhesion might be so lacking that the
lacquer
curled up in little scrolls ½ inch by 1/16 inch in diameter. Zinc feels
heavier and more limp than aluminum, at least to me. Best wishes, George

-------------------------------------



> From: John Dawson <[log in to unmask]>
> > So while we are on the topic, how about Zinc discs?
>
> Good question.  I am not sure if it was every used as a substrate in the
> lacquer era. It might not have had good adhesion and was very heavy.
> But a non-magnetic heavy disc might turn out to be zinc.
>
> Zinc had two places in phonographic history.  Berliner used it in the
> 1890s as material that was acid-etched after a groove in a wax coating
> was cut to reveal the zinc that a bath in acid would create the groove.
> This was necessary to avoid the patents that controlled cutting a
> groove.  The acid created the groove that was actually used for
> mastering or playback.  In the 1920s there was a pre-grooved zinc disc
> that you could put on your acoustical phonograph and when you shouted in
> the horn it would create dimples in the pre-groove which could faintly
> produce sound when played back.  One of these discs had the apt name of
> Echo.
>
> Mike Biel  [log in to unmask]
>