[ARSCLIST] Nitrocellulose plasticizer, or how to soften a lacquer?

[Eric Jacobs <EricJ@xxxxxxxxxxxxxxxxxxx>]

I have a fully delaminated lacquer (aka transcription disc).  
The laminate separated from the aluminum substrate long ago.  
Miraculously, it delaminated in one complete piece, no cracks 
or missing pieces.  It's an audiodisc recording blank, if that
matters.

The laminate is hard and shaped like a combination of a potato 
chip and a toroid (aka "donut").  Unplayable under any 
circumstances.  I'm not even sure that future technology like 
LBNL's IRENE could deal with such a deformed surface.

So how to get such a sound recording to lay flat?  Especially
if it is hard and brittle?

I wanted to run some thoughts and questions by the list 
related to softening of nitrocellulose laminates...

Clearly the plasticizer is what makes the laminate soft for
cutting grooves to begin with.  As the plasticizer leaches out 
of the laminate, the laminate shrinks and hardens, which in the
worst case leads to delamination and cracking.  Those mechanisms 
are reasonably well understood and accepted.

The question, then, is how to "replasticize" the laminate?

Looking to the moving image (film) community, they will soften
cellulose acetate (not cellulose nitrate) using synthetic 
camphor.  They do this with film by placing a block of the
camphor in a sealed container with the film for a number of
weeks.  Doing some quick research on camphor, I found that 
synthetic camphor is actually the plasticizer in celluloid 
(aka cellulose nitrate, the same material in a lacquer).

The next question: was camphor ever a plasticizer component 
in lacquer discs?  Has anyone ever tried to soften a lacquer 
using synthetic camphor?

After yet more research, I learned that camphor is derived 
from turpentine oil.  I'm not about to put turpentine oil on a
lacquer disc surface, but it does beg the question if turpentine 
oil might help rejuvenate a lacquer's flexibility.

More importantly, there are known plasticizers in the lacquer
laminate, such as castor oil.  This is why lacquer discs suffer
from palmitic acid and stearic acid formation.  So is castor 
oil yet another potential path for rejuvenating a lacquer's 
flexibility?

There being more questions than answers, here's a quick 
summary of the above questions in one place:

1.  How to "replasticize" the laminate? (the big question)
2.  Has anyone successfully softened a brittle and deformed
    lacquer surface? (re-phrasing of the first question)
3.  Is synthetic camphor a plasticizer used in lacquer discs?
4.  Has anyone tried to soften a brittle and deformed lacquer 
    surface using synthetic camphor?
5.  Has anyone tried to soften a brittle and deformed lacquer 
    surface using turpentine oil?
6.  Has anyone tried to soften a brittle and deformed lacquer
    surface using castor oil?

One could imagine that such a replasticizing process might 
extend the storage life of a lacquer that is awaiting 
digitization/preservation.

Although the prospects are poor for revitalizing this particular
fully delaminated, brittle and badly deformed disc, I'm still 
holding out some hope that there may be some non-destructive 
way to breathe just enough life back into this sound recording 
to allow it to be preserved.

Eric Jacobs

The Audio Archive, Inc.
tel: 408.221.2128
fax: 408.549.9867
mailto:EricJ@xxxxxxxxxxxxxxxxxxx
http://www.TheAudioArchive.com
Disc and Tape Audio Transfer Services and Preservation Consulting