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Tuesday, March 2, 2021


Take a look at what I've been dealing with since approximately 1995:
 
Errol Garner's Verve Jazz Masters 7 CD was always kept in a fresh and cool place. Steve Miller Band's Wide River CD as well. But check out what's happening to these items:

Wide River CD, Steve Miller Band, affected by CD-rot.

Errol Garner's Verve Jazz Masters 7 (1994) did not deseve this.

Nor James Brown's Sex Machine - The Very Best Of CD (1991).


In this detail of the Wide River CD, We see a mild-to-severe case of CD-ROT, a disease that's been affecting Compact Discs manufactured in the "early days". In my collection, some of the CDs manufactured by Polygram in the United States had this disease. My Stan Getz's Verve Jazz Masters 8 CD was in such a bad shape I had to throw it away, and I had to buy another copy of In The Court Of The Crimson King by King Crimson after the first song started to skip awfully. All these CDs were purchased by me in Lima, Perú, between 1993 and 1995.

CD-Rot, the worst that can happen to the digital medium, because of lousy compact disc manufacturing. The aluminum layer that reflects the light of the player’s laser is separated from the CD label by a thin layer of lacquer. If the manufacturer applied the lacquer improperly, air can penetrate to oxidize the aluminum, eating it up much like iron rusts in air.

The problem being that when the discs were cut the aluminum layer was too close to the edge of the disc and not sealed properly from the environment, thus exposing it to oxidation. The indexing information of a CD is on the inside the disc, i.e. nearest the center, and that the discs are read from the center out. This explains why in discs that succumb to CD-Rot, the last tracks on the discs are first affected, i.e. because they are on the outside edge of the disc and hence the first to be subjected to oxidation.

On playing the disc, there will be an inordinate amount of “static-like” background noise. The level of noise that can be heard rises and falls with the volume of the music on the disc. The louder the actual music, the more apparent the background noise will be. This symptom is not apparent at the outset, but eventually creeps in and gets worse and worse over time. This also seems to show up earliest on tracks towards the end of a disc rather than at the beginning.

If you hold a CD against any light and notice small holes on the surface, that's CD-Rot too. The CD, however, will play OK if the hole isn't too big (like say, a small ant). This also depends on the quality of the player.

So is the best thing you can do to make a copy of your CD? Most likely, since these CDs are non copy-protected and it would save you some money and/or hassle trying to get them refunded. Don't blame the recording industry's lack of vision but lack of lacquer. Create a WAV copy of the CD and keep it in a cool and dry Hard Drive in case CD-ROT appears. Don't forget to have a backup of that Hard Drive as well, preferably an external one of the Western Digital brand.


The following are a couple of very useful articles:

CD Rot, How & Why it Happens
HOW CD ROT HAPPENS

CD Rot occurs in some older disks that were manufactured in the technologies early days. 

The aluminum layer that reflects the light of the player’s laser is separated from the CD label by a thin layer of lacquer. If the manufacturer applied the lacquer improperly, air can penetrate to oxidize the aluminum, eating it up much like iron rusts in air.

The problem being that when the discs were cut the aluminum layer was too close to the edge of the disc and not sealed properly from the environment, thus exposing it to oxidation. The indexing information of a CD is on the inside the disc, i.e. nearest the center, and that the discs are read from the center out. This explains why in discs that succumb to CD Rot, the last tracks on the discs are first affected, i.e. because they are on the outside edge of the disc and hence the first to be subjected to oxidation.

A second cause was that some labeling inks used in the silk-screening process were chemically active even after UV curing. This interfered with the reflective layer, again, causing read-back problems.

So how can you tell whether one of your disks is infected with CD Rot? Firstly, the silver color on the “label” side of the CD will have started to change to a color variously described as bronze, copper, golden-brown or rusty-orange color. The discoloration doesn’t necessarily show up on the “playing” side of the CDs. This symptom happens on 100% of “rotting” discs, the worse the “rot” - the more pronounced the discoloration will be.

On playing the disc, there will be an inordinate amount of “static-like” background noise. The level of noise that can be heard rises and falls with the volume of the music on the disc. The louder the actual music, the more apparent the background noise will be. This symptom is not apparent at the outset, but eventually creeps in and gets worse and worse over time. This also seems to show up earliest on tracks towards the end of a disc rather than at the beginning.

Unofficial estimates put the number of affected discs at between one and 10 per cent, however the good news is that both the issues of ink and aluminium layers were solved for pressed CDs several years ago, and the CD manufacturers made changes to their manufacturing process and material selection. As a result, CD Rot should not be a common problem in the future.

CD Repair Guide

HOW TO FIX YOUR CDS FROM CD ROT

If a disc suffers from CD Rot, your first plan of action should be to demand from the manufacturer a replacement disk. CD Rot is rare on CDs but is present on older a few early discs. It is essentially a flaw in the manufacturing process and as such should be replaced.

You can carry out some repairs at home that may well solve your playback problems. To do this you will need the following:

Soft cloth

spectacle lens cloth, or if you’ve got nothing else, soft tissue/kitchen paper will do fine. Just make sure whatever you use is clean.

Rough cloth

The best I’ve had experience with is an old sock. It doesn’t want to be too rough, cotton cloths like T-shirt material is good. Good for working out those deeper scratches.

Toothpaste

Just ordinary toothpaste. Contains small bits of grit to help work away scratches. It’s not a good idea to use any kind of harsh toothpaste.

Brasso/metal polish

A bit finer than toothpaste, so you can finish off your CDs with this.

Vaseline

Petroleum jelly to fill in remaining scratches to reduce diffraction. This really does work.

Find a table or similar flat steady surface. Put a tablecloth over it, or lay some soft tissue down, and make sure the surface is clean. Yes, little bits of dried cornflakes can scratch CDs. Lay the CD silver side up on the soft surface. Make sure the CD surface is clean by using wet tissue paper or baby wipes, wiping in straight lines from the inside of the disc to the outside. (BTW, this cleaning may make your CD work now if it was just dust/dirt causing the problem). I heard somewhere that some solvents can damage the CD, but I never had any problems with metholated spirits. However, wet tissue works well anyway.

1) Find the scratches. If it’s not obvious then follow this step. Hold the CD to the light so you can all those little scratches on the surface clearly. The sort of scratches that you’re looking for are those deep enough to be easily noticeable and often run in the direction with the track on the surface (parallel to outside edge of CD). If the disc has taken on a cloudy appearance cause by many fine scratches follow the next steps using only a smooth cloth (unless the scratches just aren’t shifting) and rubbing across the sections of scratches, working in straight paths from the centre.

Try to estimate through use of the CD where the scratches are likely to be (i.e. If the skipping of an audio CD is in the first couple of tracks, or the game can’t get past the loading stage etc. then look for scratches in the centre of the disc). Now you’ve found what scratches you are going to deal with, move on to the next stage.

2) Get a small amount of toothpaste on the rough cloth (if the crack is not very deep then the smooth cloth might do)

3) Rub the cloth firmly over the scratch. This needs to be firm enough as you feel is appropriate for the severity of the scratch. However, if you rub too hard you thumb will hurt too much to continue long enough to achieve anything, and if you rub too lightly then you’ll be there all day. This may take a few minutes depending on the scratch, just keep topping up with a little toothpaste (not too much or there’ll be no friction). New scratches may appear as you are rubbing, but as long as they’ll only light scratches this won’t matter, and we’ll be smoothing these off later. When the scratch has nearly gone, or doesn’t seem to be getting better, move on to the next step.

4) If you used a rough cloth for the last step, move on to using the smooth cloth. Just do what you did before, until you’re bored or too tired to continue. Clean with water and tissue. Then move on to using the soft cloth with some metal polish like Brasso. This should smooth out some of the extras scratches you made, but may not be noticeable, so just work at that for a few minutes.

5) Next, clean the CD again using water. Then get a small amount of Vaseline on the end of your (clean) finger, and smooth across the scratch, rubbing it in a bit. It may help just going over any other scratched regions you see on the CD like this, as it will improve reading of your CD, especially on a console with a weaker laser like the PlayStation. Using some tissue or soft cloth rub the Vaseline off of the CD (in straight paths from the centre). Do not do this too vigorously or the Vaseline will be rubbed out of the scratches.

Now to test your CD. If it still doesn’t work, try again from step 2).

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