 |
 |
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:[log in to unmask]] On Behalf Of Eric Jacobs Sent: 03 August 2005 20:38 To: [log in to unmask] 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:[log in to unmask]]On Behalf Of Sam Brylawski Sent: Wednesday, August 03, 2005 11:50 AM To: [log in to unmask] 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 <[log in to unmask]> 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 > ************************************************************************** Experience the British Library online at www.bl.uk Help the British Library conserve the world's knowledge. Adopt a Book. www.bl.uk/adoptabook ************************************************************************** The information contained in this e-mail is confidential and may be legally privileged. It is intended for the addressee(s) only. If you are not the intended recipient, please delete this e-mail and notify the [log in to unmask] : The contents of this e-mail must not be disclosed or copied without the sender's consent. The statements and opinions expressed in this message are those of the author and do not necessarily reflect those of the British Library. The British Library does not take any responsibility for the views of the author. **************************************************************************