Claim: Coating the edges of a compact disc with a green marking
pen will noticeably improve its sound quality.
Status: False.
Origins: Despite
numerous claims about the efficacy of "greening" CDs, there is no
valid scientific reason to explain why marking CDs with green pens
would improve sound quality, nor has anyone ever been able to
consistently distinguish between marked and unmarked discs in a
double blind comparison.
The most commonly offered explanation for the allegedly improved
results produced by a "greened" CD is that the light from a CD
player's laser reflects off the shiny inner rim and outer edge of
the CD and enters the "eye" of the player, thereby altering the
digital bit count and distorting the sound. Coating the edges of
the CD with a colored marker supposedly reduces or eliminates the
amount of stray light reflecting of the disc's edges, producing
"better" or "cleaner" sound. (Green markers are used because the
faithful believe that color most effectively "absorbs" the light
from the laser's infrared beam.) As former Stereo Review and High
Fidelity editor David Ranada pointed out, however, light travels so
quickly that it would be reflected back to the laser from the edge
of the disc while the laser was still reading the same digital bit
and therefore could not produce a distorted reading. Ranada
confirmed his assertion by connecting a digital error counter to a
CD player to compare data errors produced during playback of both
colored and uncolored discs. He found no difference between the two
types of discs at any portion of their surfaces -- inner rim, outer
rim, or middle. He also tried coloring only half the circumference
of a disc and using an oscilloscope to analyze the signal picked up
by the laser. The scope showed no difference between the patterns
produced by the colored and uncolored halves of the disc.
The claim that coloring CDs could improve their sound originated in
late 1989, was spread at the winter Consumer Electronics Show in
Las Vegas in early 1990, and achieved national prominence when it
was printed (and given credence) in the March 1990 issue of ICE
(the International CD Exchange newsletter). The initial claims
suggested that the inner rim and outer edge of the disc should be
colored with an Eberhard Faber Design Art Marker No. 255, but over
time this procedure became less specific. (Many later reports
mentioned coloring only the outer rim, and the pen used was either
generic green or a competely different color altogether, such as
purple. Coating discs with Armor All or Rain-X were other popular
variations.)
