Re: arsclist 16" diameter phonograph disc

[Graham Newton <gn@xxxxxxxxxxxxxxxxxxxxx>]

dcampo@xxxxxxx wrote:

> I have a 16" diameter phonograph disc 1/32" thick, recorded by my
> grandparents sometime before 1937. Don't know what kind of disc it is or
> what is on it. It has 4  5/16" holes, 1 centered, 3 others set 1" back from
> center. There are some scratches and some blotches of a white substance,
> some patches slightly corrosive, most not. It has a paper label meant to be
> handwritten on, says "For reference recording only, Audio Devices Inc, New
> York".  Recorded with 2 tracks on one side, 1 short and 1 long track, about
> 2/3 full. Other side also has a label, but nothing recorded.
> I would like to have it transfered to CD, both a straight transfer unaltered
> version and a noise filtered version.
> 
> Does anyone know where I can get this done? I am in the San Francisco Bay
> area in California and would prefer a local transfer and not to ship it. But
> if I must ship, I must.

I responded to a similar private message from Margaret two days ago via my 
website, but because of the peculiarity of the recording, and for the list's 
benefit, I will post an amended extract of my reply to her below. 
Readers will note that my response also benefited from two photographs that
she had taken:-

Hello Margaret...

What you have is a 16" aluminum based "White Label" reference lacquer disc.  
In 16" discs, Audio Devices made Red Label (master grade), Yellow Label and 
White Label, which was the lowest quality "reference" grade.
The offset holes are drive holes of which really only one was needed, but 
some manufacturers punched three for convenience of the recording engineer.

It is not shellac nor plastic, but a composition of cellulose nitrate.  
The surface is decomposing, which is the white powdery substance you are 
seeing... it is palmitic acid, a byproduct of the decomposition of castor oil
that was used as a plasticizer in manufacture of the lacquer coating.
It is a mild compound primarily used in the soap-making industry.

The disc was likely recorded in some professional facility like a radio 
station or recording studio since "home" disc recording equipment was not 
equipped to record a 16" disc, that being the realm of the professional.
It is likely recorded coarse groove, at at 33 rpm, with good recording 
levels which is an advantage for starters, and it appears to contain about 
15 minutes of recording time.  


NOTES:

(These are offered from experience transferring hundreds of similar 16" 
lacquers over the years.

1.  A suitable modern turntable should be used to avoid the rumble and noise
    of the old transcription turntables that were in common use when this
    disc was likely made.

2.  The palmitic acid deposits MUST be properly cleaned off BEFORE any 
    attempt is made to play the disc.  Failure to do this will cause 
    further and irreparable damage to what is already a fragile artifact.
    Portions of the aluminum base, outside of the grooved area, are exposed 
    and are corroding.
    I use a Keith Monks "Archivist" record cleaning machine and appropriate
    chemistry for the cleaning job.  Because of the surface decomposition,
    the playback of the cleaned disc will have a higher level of hiss than 
    a lacquer in good condition to begin with, but CEDAR de-hiss will handle
    most of that problem. 

3.  A good selection of styli is needed to find the one which will provide 
    the most quiet play of the disc before application of ANY noise reduction
    attempts.  Something in the range of 1.5 through 2.5 mils, truncated and 
    or elliptical will likely be needed, and in some possibly abnormal cases 
    up to 4 mils. A 2.0 mil truncated elliptical stylus is a good starter.

4.  Noise reduction will be needed to produce the best output, and will 
    require de-click, de-crackle and de-hiss processes for best results.

5.  Workstation editing will likely be required to remove larger disturbances
    that are outside what the noise reduction equipment is designed to handle.  

Generally the results of this kind of work are very satisfactory.

Shipping lacquers shouldn't be a problem provided they are packaged properly,
and I can provide suitable packaging instructions if needed.


... Graham Newton

-- 
Audio Restoration by Graham Newton, http://www.audio-restoration.com
World class professional services applied to phonograph and tape
recordings for consumers and re-releases, featuring CEDAR processes.