Does coloring the edges of CD's help the sonics?

The straight green marker and other green products approach does not work. You need to start with a layer of yellow, then a layer of blue, finished off with a final and yet lighter layer of yellow. While the end color is green, it is the layering of the blue and the yellow that is addressing the stray laser and preventing it from being reflected back onto the read surface of the disc. Additionally, if you find that the slit between the drawer mechanism and the face plate of your CDP seems a bit large, I have found that placing 16 layers of electrical tape in alternating colors of yellow blue yellow also greatly improves the sound of a new CD when you put it in your player. But perhaps it is the hour long process of removing the tape, removing the old CD, spending lots of time waiting for the marker layers to dry before applying the next and then putting all that tape on that makes me so eager to listen that I just think it sounds better.

With regard to trimming the discs, I suspect that doing this is for reasons other than "balancing" the disc. My company manufacturers equipment for the optical disc industry where we have an 85-90% worldwide market share. Every disc that is manufactured goes through rigorous in-line inspections with lasers, etc. . . Part of this process includes the scudderer which is part of the chemical distribution process of coating the disc. Beside the injection molding process, the scudderer is the area of disc replication that causes the greatest amount of rejected discs. Based on this, my suspicion is that a less than perfect distribution of the coatings is what is to blame for inbalanced discs. Could this be a build up at the very outer edge of the disc? Sure, but since it would be unusual for an inbalanced disc to pass tolerance inspections by later and testing equipment, the likelihood that all the planets would align and the "truer" device would correct the problem is not going to be very high. Only a very small percentage of discs should need to be trued, as they should have been rejected in-line (typical disc rejection rate varies from 6% down to about 2-3% at the best plants).

As for shattering the discs with the "disc truer", I would be very surprised by this. Polycarbonate is very hard material and quite difficult to shatter. As part of a developmental project, we build several disc eraser units for Microsoft to use at the lines (versus away from the lines, such as in a warehouse - were we alread make disc destruction systems that are required by Microsoft if a vendor company replicates discs on their behalf). The disc eraser prototype systems ran the disc between two special surfaced rollers under very high pressure and made the discs impossible to read (the key being that no dust was produced, allowing them to be run directly at the production line). Never once during this testing process did we have a disc shatter or break, even during a malfunction of the equipment. One can moderately easily break or shatter a disc in ones hands, but this requires bending the disc beyond the point of strength of the PC, which while not tough is not something one would do as a mistake. In most cases, you could take a hammer to a disc wih light to moderate force without the disc shattering, unless the edge of the hammer is used and the disc is not on a flat surface.

While I joked about the green edges above, I do actually use a CD absolver mat when playing CDs. How much good does it do? It has been so long since I started using it, I can't honestly say that I know it makes any difference. But it has become habit.