Dear List members
One of the options for long term storage of information is CDR.   The
British Antarctic Survey provided the following notice about the dangers of
relying on this medium. Have there been other observations on deterioration
of CDR? or suggestions for precautionary measures?
Baruch Spiro

The following important information relates to CD-R recordable discs:
Ideal long term storage conditions for CDR's (this does not include factory
pressed media such as music CD's)
1: relative humidity of 35 - 45 %
2: temperature of 13 - 19C
3: disks must be stored in a 'pollution scavenging paper' not the plastic
jewel cases (eg: micro-chamber envelopes from Conservation Resources,
Cowley)
4: 24hrs should be given for the CDR's to acclimatise before use in a warm
office

if the above is followed tests show that the expected life of the CD will be
around 20 years.

If you keep to the same conditions but put the CDR disks back into the
plastic 'jewel' cases the life expectancy of your data can drop as low as 3
to 4 years ... yep ... three to four years

Factors causing the CD's to degrade

1: the main factor is the chemistry of the ABS plastic that the plastic
insert (the section that holds the disk) within the jewel cases are made of.
Tests show that the gas build up inside the case can reach a pH of 2.
2: use ! ... the disks are written using an 800w laser and read by a 600w
laser, this is sufficient to slowly damage the surface ... the disks
effectively wear out !
3: If you write on the case with a solvent based pen this will again
accelerate the disks demise. Writing on the disk with any pressure at all
can damage the data ... the data is stored on a thin layer just beneath the
label surface not on the bottom silver/gold side! ... The advice given to
me, is that if you have to write on the disk, use a soft non-solvent based
felt tip pen.