CD jewel cases

Karl Gillies <karl.gillies [at] southlandmuseum__co__nz> writes

>Mention was made of jewel cases gassing off degrading compounds--I
>thought most jewel cases were usually made of stable polycarbonate,
>or am I wrong? ...
> ...
>So, is there an inert 'archival' type of plastic jewel case
>available?

My recommendation is to go with the standard sized jewel case and
not the thin ones.  I would avoid any type of sleeves as they do not
protect the CD surfaces as well as a standard jewel case.  I believe
the off-gassing issue is more with the printed material within the
jewel case.  Those glossy printed booklets or sheets do off-gas and
leave deposits on the disc.  In many cases these deposits can be
cleaned off, but if any corrosive volatiles are present they can
damage the disc.

I had Scott Williams at CCI analyze 3 types of jewel cases for me.
It was only a small random sampling and may not represent all the
jewel cases out there, but I believe they are fairly standard.  Here
are the results:

CD jewel case (regular): rigid clear colourless plastic top and
bottom with flexible black plastic tray inserted into bottom.

    *   top and bottom: polystyrene homopolymer
    *   black tray: polystyrene with a few percent of polybutadiene

DVD jewel case (sturdier): rigid clear colourless plastic top and
bottom with flexible grey plastic tray inserted into bottom.

    *   top and bottom: polystyrene homopolymer
    *   grey tray: polystyrene with a few percent of polybutadiene
        (slightly more butadiene than Case 1)

CD jewel case (slim): rigid colourless plastic clear top and frosted
bottom.

    *   top and bottom: polystyrene homopolymer

According to Scott: The polybutadiene is there to increase impact
resistance.  As far as he knows, polystyrene and polystyrene with
polybutadiene are very stable and do not cause any problems due to
their degradation.  The polybutadiene component is an unsaturated
aliphatic hydrocarbon and is therefore subject to oxidation at the
C=C double bonds.  This leads to carbonyl functional groups on the
polybutadiene polymer backbone, but not to corrosive volatile
compounds.

Joe Iraci
Canadian Conservation Institute


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                  Conservation DistList Instance 17:39
                Distributed: Wednesday, October 29, 2003
                       Message Id: cdl-17-39-007
                                  ***