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Wash, Cut, Polish & Demagnetize

As I sat and read through the most recent threads on the "Agon" forum, I noticed a thread regarding "Glossary of Audio Myths". I noticed several comments regarding "greening" and demagnetizing CDs.

Without delving too deeply into the effects of laser light diffraction, deflection, dispersion and reflecting light from adjacent tracks creating "jitter", and to avoid reduntantly examining the fact that the aluminum "wafer" in a CD is not always just aluminum, but in many cases aluminum "alloy", I would like to attempt to dispel a few of these "myths".

Many CD manufacturing facilities use a coating of mold release agents on the manufacturing machinery and on the plastic substrate material in the actual CD to facilitate ease of handling throughout the manufacturing process. Somewhat similar to spraying a cooking pan with "PAM" to reduce sticking. The residual amounts remaining on the CD upon completion of manufacturing should be removed as it will cause minor deflection and loss of focus of the laser beam. Specialty chemicals are available specifically for this purpose. I wash the CDs thoroughly using Dawn dishwashing liquid and very warm water. I cannot confirm that this process is as effective as using the specialty chemicals, but it leaves the CD surface extremely clean and seemingly free from any "oily" feel.

I then cut the edge of the CD using an Audiodesk CD cutter. This process reduces the amount of laser scatter from exiting through the outer edge of the CD and flooding the inside of the CD transport with reflected laser light. By cutting a bevel on the edge of the CD, you actually reduce the edge surface area by which the diffracted laser light can disperse. Some may feel that this a bit excessive, but we must keep in mind that the results of these treatments are cumulative.

The next process involves applying CD "Green" to the beveled edge. The properties of the color value of the Green used in the majority of these coatings tend to absorb any stray laser light. I still, to this day, have not been able to figure out why Green is the color of choice although, I have been told that it is simply the values of each of these colors (Red laser light and Green) that work together in unison to "neutralize" the light. The initial washing of the CD also helps to enhance the adhesion of the green coatings.

Upon allowing the CD green to dry, I then apply CD diamond using 100% cotton balls, and polish using again, cotton balls. CD diamond is an optical enhancer similar to Optrix,
Vivid, etc. and also contains a anti-static component. Most of these "optical enhancers" work by simply filling in microscopic pores in the CD surface permitting a more direct transmission of the laser beam through the plastic substrate material to the actual CD surface.

The last step involves demagnetizing the CD using a Furutech RD-2 CD demagnetizer. CDs, contrary to what most people believe can and will become magnetized. The results are a less black background, a general "haze" and loss of detail. If Cds were made using pure aluminum with NO trace elements, this step might not be required.

The results of all this? Pretty damn amazing. Again, recognizing that the results of all of these steps are cumulative, when all is said and done, the improvement is quite significant. Although these steps may sound somewhat time consuming, each CD actually only takes about three minutes to complete.

I hope I have provided some insight as to "dispelling" some of these myths. I can, and will, stand by this process as time and time again these enhancements have made CDs a lot more listenable. And, I have dropped the jaws of many non-believers after they have heard the actual results.

Any comments regarding this process are welcome. Happy listening.


buscis2

Showing 6 responses by herman

herman
2,280 posts
 
I may be able to shed a little "light " on this.

"I still, to this day, have not been able to figure out why Green is the color of choice although, I have been told that it is simply the values of each of these colors (Red laser light and Green) that work together in unison to "neutralize" the light."

The correct term is absorb, not neutralize. A green marker is green because it reflects green and absorbs other colors such as red. Since red and green are opposites on the color wheel, green is especially good at absorbing the red. Black should also work because it absorbs all colors. If you used a red marker it would reflect red, exactly the opposite of what you want.
herman
2,280 posts
 
Sorry to hijack this thread with a discussion of physics, but I have done a little research into the subject of light absorption and have found the following.

Light will be absorbed by a system when the frequency of the light is in resonance with some natural frequency of that system. When light is refracted, it's speed changes and so does the wavelength, but the frequency does not. Therefore the absorption of a material is independent of the wavelength.
herman
2,280 posts
 
HI Buscis, I don't disagree with the results you claim as I have no first hand knowledge, but again it is a matter of terminology. If you shine a pure blue light onto a yellow surface the surface will appear to be black because it does not reflect any of the blue light. There is no cancellation, the blue light is simply not reflected so there is nothing to see.

To Geoff, yes it is infrared but 790 nm is barely outside the visible spectrum so it too will be absorbed by most green surfaces. As to being downshifted, in most cases, a laser entering a material will exit that material at the same wavelength. If it slows down as it enters the medium, it speeds up as it exits. There are a few materials that re-radiate laser energy at harmonics of the incident beam such as KTP crystals that convert a 1064 nm Nd yag laser to 532 nm, but light entering a compact disc comes out the other side at the same wavelength.

I offer this not in the spirit of disagreement, but in the spirit of attempting to clarify.
herman
2,280 posts
 
Sean, I am not a laser engineer so I can't give definitive answers but I do have a bit of laser experience as I make my living repairing medical lasers. I do have few thoughts on the subject.

Some energy is reflected and some not. That is the way the whole scheme works. Areas that reflect enough light are interpreted as one digital state and those that don't are interpreted as the other state.

When I point my red laser pointer at a disc I see that it scatters the light. Depending on the coating or lack of coating on the top of the disc some discs transmit a portion of the light. I can see it through the disc. Those that have a heavier coating of paint seem to block it. I have no way of knowing if they absorb it or reflect it. The pointer is a shorter wavelength than the laser in the CD player (around 650 nm vs 790 nm) but they are close enough to reasonably assume that they would act in a similar fashion. It is possible to coat a surface with materials that will act upon a narrower range of wavelengths than this so it is possible that my assumptions are wrong.

The big question is whether this scattered/reflected light will be picked up by the sensor in the player and cause errors. It seems like it would be very simple to set up test equipment to capture the bit stream from a digital output and see if it changes with various disc treatments. I don't have this type of equipment so I can't do it but it can't be all that difficult for someone who does. It would be interesting to see what the results of such tests were.
herman
2,280 posts
 
It might be better to ask an ophthalmologist.
herman
2,280 posts
 
I found this site about how compact discs work that may shed a little light on the topic.
More to discover