Over polished DVD ?

[Ralph]

Is it possible to over polish a CD/DVD ?
One of my local Video outlets cleans every DVD they rent out when it is returned. They put it in a fancy (costly) machine with a touch of "paste" and let it polish for a while. There doesn't appear to be any post cleaning application of a protective layer (ie like you would with car polish / wax after cleaning the car).
The discs never show any scratches or marks and yet 50% of their discs skip while playing. They skip whether it played in my DVD player (Marantz) or in any of my 3 different computers. On close inspection, the surface is sometimes more matt than reflective in patches.
I have tried to repolish them using a manual machine with a "protect" solution which gives only a slight improvement.
I have known the store owner for many years and would like to approach him on this with a considered opinion.
Any thoughts ?

RalphH

[Decky]

You cannot over-polish but you can over-scratch it with a wrong polishing liquid or damaged polishing wheel surface. The surface of the disk has to be transparent so to minimise dispersion of the incident laser light. Laser is focused under the surface but any diffusive surface finish will cut the amount of light passing through it therefore there will be less light reflecting from the etched layer, less light passing back to the receiver and you S/N ratio goes to 0.

I managed to improve some of the scratched disks with toothpaste and micro-fibre cloth. For finishing I used micro-polish liquid for cars. After that I clean the disks with water and IPA (iso-propyl alcohol)

[2sheds]

You can over polish a DVD. Polish is, after all a mild abrasive. And if this 'machine' cleans the DVD's in a circular motion (rather than across the CD as recommended), it would explain why half of the DVD's skip.

P.S. Love your magazine

cheers
2sheds

[emesbee]

I certainly think it is possible to over polish a DVD, which could lead to skipping.

Another thing to consider is the possibility of the laser in your DVD player wearing out. If you've had your player for a while, then the laser may have lost strength (I think that is what happens), making it less tolerant of flaws and imperfections in the disc.

I had a CD player where that happened. Initially it started skipping at specific points on certain discs. It got progressively worse over time, until nothing was playable in the end.

Its obviously not an issue if the player is fairly new. I only mention it as a possibility.

[joz]

From what I have seen is that they polish them to remove scratches,so by grinding away the higher part of the disc.
They shouldn't be polishing every disc every day.

[nickonsound]

You can polish your cds at home, you can use a jewelry polishing cloth, the one that has 2 types: one for cleaning and another for polishing.