Re: [ARSCLIST] Acetate disc sleeves

[Eric Jacobs <ericj@xxxxxxxxxxxxxxxxxxx>]

Luann:

Thank you for your cogent explanation, and which inspired some
further research and thinking on my part.  I may very well be able
to answer my own question...

Where acetate discs differ from acetate film is in their use of
plasticizer and the failure mechanism.

I do not believe that castor oil was used as a plasticizer in nitrate
film stock, instead it may have been phthalates or other plasticizers
like camphor oil (which is more stable than castor oil).  However,
castor oil - and lots of it - was used as the plasticizer in acetate
discs.

Another point of confusion is that most "acetate" discs do not actually
contain acetate.  The very earliest transcription discs were indeed
manufactured from cellulose acetate, but since the 1930s these discs
were made of cellulose nitrate, but were still referred to as
"acetates" even though this is a misnomer.

So I'm just not confident to what degree acetate film and acetate discs
can be compared.

Acidic environments are generally a problem for most materials, and
acetate discs are no different.  According to the ARSC journal article
"Selected Acetate Disc Cleaning Methods" (1997, Paton et al):

"...we propose that the castor oil used as a plasticizer reacted with
water vapor in the air (humidity).  In the presence of water vapor,
one or more of the ester bonds can hydrolyze, releasing the various
carboxylic acids.  This process is accelerated when acids are present
and the PH of the acqueous environment is below 7."

The carboxylic acids that are formed are palmitic acid and stearic
acid, a white greasy film that develops on improperly stored acetate
discs, and that most people on this list are all too familiar with.

Here is my thinking:

1.  The macro environment is most important - stable temperature and
    low humidity - in order minimize the exuding of castor oil
    plasticizer from the disc.

2.  Plasticizer loss is unavoidable over time, so the next level of
    protection is (a) lack of water and (b) a non-acidic micro
    environment to slow formation of carboxylic acids (palmitic and
    stearic acid).

3.  The great unknown factor: what, if any, acidic compounds are
    released from the nitrocellulose disc?  If the nitrocellulose
    can create an acidic microenvironment, then air circulation
    and a well-buffered container will be important.  If not, then
    it may be more important to provide a vapor barrier to
    minimize hydrolysis of the castor oil into carboxylic acids
    (palmitic and stearic acid) in the first place.

Really, I believe item (3) above is the crux of the matter.
According to Pickett and Lemcoe, 1959:

"The most signficant decomposition product [of cellulose nitrate]
is nitrogen peroxide which is converted into nitrous or nitric
acid in the presence of liquid water and, since an acid has a
catalytic effect on the degradative reactions, this is an
autocatalytic reaction."

So once again, the primary movers in the degradation process are
(a) water and (b) acids forming by the reaction with water.

Based on the Pickett and Lemcoe research, as well as the research
done by Paton et al, this simply reinforces the importance of
having a dry environment for nitrocellulose discs to minimize the
formation of acidic compounds from the decomposition of the
nitrocellulose (forming nitric acid) and the castor oil (forming
carboxylic acids).

Because a water-free environment is impossible to create, and may
have undesirable side effects, the formation of nitric acid and
palmitic and stearic acids over time are unavoidable.  But the
autocatalytic effects that accelerate degradation can be minimized
through the use of a properly buffered, acid- and lignin-free
sleeve.  Air circulation can help dissipate acidic vapors, but
since you cannot necessarily count on air circulation in a record
stack, the higher pH buffer will be the first line of defense
against the acid formations.

Based on this conclusion, polyethylene inner sleeves are not
appropriate for acetate/nitrocellulose discs because they lack
any buffer properties.  The best sleeves for a 16-inch acetate
disc would then be (but not restricted to):

Gaylord GH-LP17 ($1.31 each in small quantities)
Conservation Resources EN-1717LP ($1.08 each in small quantities)
Metal Edge PRSA16 ($6.24 each in small quantities)

The Gaylord and Conservation Resources products appear to be
very similar.  The Metal Edge product is a two-part solution with
an inner and outer sleeve, and is constructed of heavier
material and has a die-cut window for viewing the label through
the clear outer sleeve.

The Metal Edge product may actually provide the best of both
worlds with a polyester outer sleeve (vapor barrier) and a
buffered acid-free inner sleeve.

But if you have a well-controlled macro environment for storing
your discs, the Gaylord and Conservation Resources products should
work very well, too, especially given their more favorable
pricing.

Eric Jacobs
The Audio Archive
http://www.TheAudioArchive.com



-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx]On Behalf Of Luann Schneider
Sent: Wednesday, August 03, 2005 9:26 AM
To: ARSCLIST@xxxxxxxxxxxx
Subject: Re: [ARSCLIST] Acetate disc sleeves


Eric:

As Richard pointed out, today films are being stored in ventilated cans for
a variety of reasons with the main rationale to help prevent vinegar
syndrome.  Ventilated cans permit the dissipation of acidic decomposition
by-products from the film can which in turn encourages the diffusion of the
by-products from the film pack.  This is important because the acidic
by-products are a catalyst for the decomposition reaction and thus
accelerate the reaction.  ProVent and ProVent Audio containers are
ventilated to allow the film and audio tape to "breathe".  Hope this helps.

Luann Schneider
Tuscan Corporation
info@xxxxxxxxxxxxxx
www.tuscancorp.com
ph:  847-458-7280
fx:  847-458-7281

-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx]On Behalf Of Richard L. Hess
Sent: Tuesday, August 02, 2005 9:41 PM
To: ARSCLIST@xxxxxxxxxxxx
Subject: Re: [ARSCLIST] Acetate disc sleeves


Eric,

I am sure there is room for debate, but films are being stored in
ventilated cans these days for a variety of reasons.

You might browse
http://www.stildesign.com/english_site/pages_eg/articles_eg.htm

I think Hollywood Vaults and the National Film Board of Canada are
using this product -- at least for some of the storage.

You might ask over on the AMIA list for this.

Cheers,

Richard

At 09:33 PM 8/2/2005, you wrote:
>What are your preferred sleeves for storing acetate (nitrocellulose) discs?
>
>Here's the debate (per "Preservation and Storage of Sound Recordings",
>Pickett and Lemcoe, 1959):
>
>1.  The deterioration of nitrocellulose is accelerated by moisture
>2.  The deterioration of nitrocellulose is accelerated by lack of air
>circulation

Richard L. Hess                           email: richard@xxxxxxxxxxxxxxx
Vignettes
Media                           web:   http://www.richardhess.com/tape/
Aurora, Ontario, Canada             (905) 713 6733     1-877-TAPE-FIX
Detailed contact information: http://www.richardhess.com/tape/contact.htm