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Rapid freezing can cause multiple microcracks to form in the polycarbonate
surface. Propellant ejection from compressed air duster cans will cause this
effect.  If this is happening, and the disc is still readable, make a copy.
Do not attempt to clean the disc.

Jerry
Media Sciences, Inc.

> -----Original Message-----
> From: Association for Recorded Sound Discussion List
> [mailto:[log in to unmask]] On Behalf Of Prentice, Will
> Sent: Monday, June 27, 2005 12:29 PM
> To: [log in to unmask]
> Subject: [ARSCLIST] Frosted CDs
>
> We have two sets of "The Complete Caruso" (GD60495), a 12 CD boxset in
> the RCA Victor Gold Seal series, published in 1990 and manufactured by
> BMG Music, New York. One is suffering from a problem I haven't come
> across before.
>
> The two sets are largely identical, although the label (upper) side of
> the discs in one set is printed in gold on red, and features what
> appears to be a date amongst the hub data: 10/90. The discs in the
> second (later?) set are printed in black with no background colour, and
> have 6/93 in the hub data.
>
> The 10/90 set have a curious crystalline frosted effect on the underside
> of the discs, rendering them unreadable. The interesting thing is that
> the frosting is on the outside of the polycarbonate, i.e. NOT in the
> metal reflective layer, where other problems such as bronzing manifest
> themselves. When gently rubbed with a lens cloth the frosting
> (crystals?) seem to come off, although I haven't attempted to clean an
> entire disc and play it, for fear of causing further damage. It appears
> to be a result of the exposure of the polycarbonate (or some element of
> it) to something atmospheric.
>
> Has anyone come across this problem? The 6/93 set is unaffected, while
> all the discs in the 10/93 set are affected to roughly the same degree.
> The two sets have different storage histories, but no other discs stored
> near the affected set show any such problem. The affected set have AFAIK
> been stored under archival conditions by us since they were purchased
> new.
>
> Thanks
>
> Will
>
>
> ...................................................
> Will Prentice
> Technical Services
> British Library Sound Archive          Tel: +44 (0)20-7412-7443
> (formerly National Sound Archive)    Fax: +44 (0)20-7412-7416
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> London     NW1 2DB     UK            http://cadensa.bl.uk (online
> catalogue)
>
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