Re: [AV Media Matters] The Functions and Science of 'CD Polishing'.

[Graeme Jaye <gjaye@retemail.es>]

Hi Ed

Since I have just replied to another post on this subject, I would
only like to pick up on a couple of points you raised.

e> But the unintended penetration of water through the porous
e> polycarbonate and protective lacquer layer

*Is* polycarbonate 'porous'?  It is my understanding this is not the
case.

The question of destroying the reflective coating through damage to
the lacquer integrity is a more serious issue, I grant - but I have
seen no evidence of this so far.  Obviously more work needs to be done
in this area - certainly from the point of view of archival use.

e> The standards of successful treatment to recover music from a CD is
e> not the same as that of a disc used to preserve valuable heritage
e> content.

True - but, as far I am aware, no manufacturer of such devices has
made a pitch at the archival market.  Possibly, this is because the
requirements which would be placed on the machine in question would
raise its cost to a point where no one could afford it anyway :-).

e> It now remains to identify a liquid that can be applied to a
e> damaged CD reading surface, that has in its dried state the
e> matching refractive index. From the reports we have, it would
e> appear that  the existing solutions that have been formulated have
e> their limits.

There are products using this principle on the market.   Generally,
they are not long-term effective as the dried matter (whatever it
might be) will detach itself from the disc at some time.  They are not
really to be classified as 'repair' systems. in my view.

e>This wet state content transfer in printing  or telecine transfer
e>has become the most desirable solution for dealing with  scratched
e>film base surfaces.

Perhaps someone out there is already working on a 'wet gate' CD player
- we can but hope :-)

e> Whether this disc surface 'rejuvenation' happens while the
e> polycarbonate is in a softened state is doubtful, nor is it
e> advisable because softening would disturb the sandwich structure of
e> the bonded disc surfaces.

No - the process is purely a mechanical grinding of the surface.  One
of the major reasons for the presence of water is to conduct the heat
so generated away from the disc.

As it happens, there was a manufacturer who proposed to 'repair' discs
by re-heating the surface, so that it all flowed together and took out
the scratches.  Not much has been heard about *him* lately :-)

e> 9. In all cases, users who have damaged discs that are causing
e> drop-outs, are advised to use the services of commercial testing
e> services to benchmark and do a quality evaluation of their disc
e> before choosing the 'polishing' or any other 'rejuvenation' method
e> of their choice.

As a direct result of the discussion which has been taking place here,
I am seriously considering doing this for my own interest. Obviously,
I can not do this on behalf of the manufacturers I represent (although
I expect they would be interested in the results, particularly if
favourable).

However, although I am sure there *is* someone here with the necessary
equipment and a bit of spare time (not to mention an acceptable rate
for the job) I have yet to find them.

e> Because the people whose services or products are focused on
e> consumers, have not provided us with reliable information to go by
e> that will enable us to predict whether a solution will solve a
e> particular problem or not.

There is, of course, nothing to stop anyone here asking the question
of the various manufacturers of these devices.

Graeme Jaye

gjaye@retemail.es

Audio Restoration and CD Repair
http://www.personal-cd.com