[ARSCLIST] DJ dubplates (was: Acetate disc sleeves)

["Prentice, Will" <Will.Prentice@xxxxx>]

Eric, your thorough pursuit of the question has been really useful to me
and most likely many others. Thanks. 

The discussion brought to mind another question. What kind of lacquer is
used on DJ dubplates today? Is it a form of cellulose nitrate similar to
the Audiodiscs etc of past decades, or has the science moved on
significantly? The term "acetate" is still commonly (and unhelpfully)
used, and there are now variations available such as "reference lites"
which claim to be as light as vinyl but tougher than the standard
lacquer disc. 

Anyone know? A lot of material used by DJs makes it onto lacquer disc
without a subsequent pressing or commercial release, so I suspect the
number of these arriving in archives may start to increase again in the
coming years. 


Thanks

Will Prentice
   

-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx] On Behalf Of Eric Jacobs
Sent: 03 August 2005 20:38
To: ARSCLIST@xxxxxxxxxxxx
Subject: Re: [ARSCLIST] Acetate disc sleeves

After careful re-reading of both Pickett and Lemcoe (1991 version)
and Paton et al (1997), I've reached the conclusion that an acid-free
buffered (higher pH) sleeve will provide the best localized defense
against acetate disc degradation, and that a polyethylene or polyester
inner sleeve is not appropriate for acetate discs because it lacks
the ability to neutralize acids.

The primary degradation reaction is hydrolysis, which is unavoidable
in any long-term environment.  Both the nitrocellulose and the
castor oil plasticizer break down into acids (nitric acid, and
palmitic and stearic acids respectively), and these acids in turn
accelerate the degradation process.  Since the acid formation is
inevitable, neutralizing the acids is the best you can do to slow
the deterioration.

The LC-designed sleeves from Metal Edge appear to be more apt to
form a micro-environment with their 3-mil polyester outer sleeve
that can act as a vapor barrier.  Any moisture trapped in the
sleeve cannot escape (bad).  Of course, any new moisture is also
less likely to get in (good).  So my feelings about the polyester
outer sleeve are mixed.

The paper-based sleeves from Gaylord and Conservation Resources have
the advantage of breathability, so that if any moisture finds its
way into the sleeve, it may find a way out through the porosity of
the paper - provided that the macroenvironment humidity is well
controlled (as it should be).

Ultimately, I will be using the Gaylord and/or Conservation
Resources sleeves on my project - not only do they cost less than
the Metal Edge sleeve, but in an environmentally controlled
storage area, I perceive the lack of a vapor barrier as an
advantage rather than a disadvantage.

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



-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx]On Behalf Of Sam Brylawski
Sent: Wednesday, August 03, 2005 11:50 AM
To: ARSCLIST@xxxxxxxxxxxx
Subject: Re: [ARSCLIST] Acetate disc sleeves


Brandon is right, of course. When ARSC ordered a reprinting of Pickett
& Lemcoe a year or two ago, we wrote a new preface to the report
warning specifically against the recommendation to seal lacquers in a
sleeve.

Sam


On 8/3/05, Brandon Burke <burke@xxxxxxxxxxxxxxxxxxx> wrote:
> Eric,
>
> You know... The more I think about it, the more I'm convinced that
> "sealing" the disc in it's housing -- what one would essentially be
doing
> in this case -- is a really a bad idea.
>
> We already talked about micro-environments on Monday but I'll say
again
> that sealing the disc within its housing allows off-gassing and other
> byproducts of degradation to compound this problem -- perhaps even
> exponentially!  It also seems to me that if the discs are stored at
> reasonable archival conditions (let's say <50% RH) there's less of a
need
> to keep moisture out.
>
> Echoing what Richard said earlier today, I think I'd prefer to have at
> least some airflow within these housings.
>
> Brandon
>

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