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From: Emily Harrison Kelly
Date: 11 May, 1996

CD Marking: Is it as dumb as it sounds or is there something to the fad?

From the AFU FAQ:
F. Coloring your CD's rim with (special) marker will enhance sound quality.

Background:
The UL is that marking the rim of a CD with a magic marker affects the passage of light through the CD and provides a clearer, richer sound quality. The marker color specified is usually green, and one source goes so far as to specify an "Eberhard Faber Design Art Marker No. 255, a blue-green" (USA Today 1990/05/10, D4).

Current AFU status:
False. No satisfactory mechanism has been shown whereby this could happen, and apart from individual testimonials, it doesn't even seem to work for most people. As has been pointed out on the group, CDs are a digital technology, and the laser either can or cannot read the numbers. If it can, the sound is a perfect reproduction; if it cannot, the CD skips. "Improving the sound quality" is impossible.

Some references and comments:

From: bradham@panix.com (Bo Bradham)
Newsgroups: alt.folklore.urban
Subject: Re: Marking CDs
Date: 3 May 1996 16:41:24 -0400

This is all I could find:
Fantel, Hans. Brush Aside the Idea of Painting CD's.--Commentary. New York Times: Jun 3, 1990, 2, 26:3 Hans Fantel discredits the trendy idea that painting the edge of a CD green improves the sound quality, and warns that it might ruin one's CD collection.

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From: iayork@panix.com (Ian A. York)
Newsgroups: alt.folklore.urban
Subject: Re: Marking CDs
Date: 3 May 1996 17:03:42 -0400

The rec.audio.high-end FAQ file at
http://tkiwww.kub.nl:2080/tki/Docs/Projects/Arthur/Rahe/cd.html pooh-poohs this myth as well:

"Scientific studies of the data coming off of the disc have failed to show any difference between a virgin disc and a green painted disc. I have not heard of double blind listening comparisons that have proved that there are people who can hear the difference, although many have performed uncontrolled tests with positive results."

Unfortunately there are no cites here pointing to the studies in question.

Anyway, apparently the believer's rationale for this is "if you put a green stripe on the very perimeter of the disc, then the light beam will not reflect around inside the disc and will more clearly pick up the data". So there is a rationale, even though it sounds like a pretty whacky one.

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From: sean@panix.com (Sean Willard)
Newsgroups: alt.folklore.urban
Subject: Re: Marking CDs
Date: 4 May 1996 12:12:58 -0400

Ian A. York <iayork@panix.com> writes:
|
| Anyway, apparently the believer's rationale for this is "if you put a | green stripe on the very perimeter of the disc, then the light beam will | not reflect around inside the disc and will more clearly pick up the | data". So there is a rationale, even though it sounds like a pretty | whacky one.

Yup. First of all, to cut down on total internal reflection, you'd need to coat the CD with a substance whose index of refraction is somewhere between that of the disc's and that of air. Thus the most crucial property of the pen would be the index of refraction of the dried ink. I believe most CD players use red laser diodes, which means that green ink would tend to absorb the light, but this doesn't matter; if you used red ink, or clear, the light would be transmitted through the ink, which would be just as good.

Secondly, any light that did internally reflect would have to be at a very shallow angle; any scattered light that did manage to propagate from the laser's position all the way out to the rim would hit the rim with a large enough angle as to just pass through, coating or no.

There *is* some light bouncing around, having scattered off the pits in the reflective surface; that light, reflected back toward the photodiode by adjacent pits, would be a much better candidate for interference---and it's obviously not a problem.

Sean ``Zen and the Art of Total Internal Reflection'' Willard

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From: ekelly@acpub.duke.edu (Emily Kelly)
Newsgroups: alt.folklore.urban
Subject: Re: Marking CDs
Date: 3 May 1996 23:25:37 -0400

P Tampas <ptampas@fss102.fs.ford.com> wrote: >I don't intend to re-open this debate. Can someone point me to some
>authority on this issue?

Authority, hell no! But I do have a USA Today article by Bruce Schwartz, from May 10, 1990 (page D4), and headlined "Felt-tip markers stir a hue and cry over CD clarity". It was the only article that turned up when I did a keyword search of Duke's online Newspaper Index for "compact", "disc" and "marker".

It's not a terribly scientific article (fancy that), and it spends more time dubiously quoting gushy believers than it does discussing whether or why the marking works or doesn't work. Some of the quotes do unwittingly outline the ULish attraction of the myth:

        "It's amazing that you can improve billion-dollar technology 
        with a two-buck marker,' says Pete Howard, publisher of 
        _International CD Exchange_, a monthly newsletter...  

        Adds Sam Tellig, writer for _Stereophile_, a high-end audio 
        magazine: "I get a great deal of satisfaction in showing that 
        these tweaks take the 'perfect-sound-forever medium' and make
        it a little more perfect."

One oddity of this article is that it calls the marker "turquoise" instead of green--in fact, it goes so far as to specify an "Eberhard Faber Design Art Marker No. 255, a blue-green". Had we heard this before?

But the author exhibits a healthy skepticism, and he quotes a _Consumer Reports_ debunking of the similar home improvement of self-adhesive rings that rim the top outer edge of the disc and supposedly give it more rotational stability (according to Consumer Reports, the ringed discs actually mistracked more than plain ones). And there are some nifty illustrations on How To Clean Your CD, too.

Moreover, USA Today seems to share AFU's enthusiasm for home experimentation, even though this one doesn't involve soda cans or motorcycles, so I don't think Ian and Harry need to worry about job security at AFU Labs, Inc. From the little boxed sub-article in the corner of the page:

SHADES OF DIFFERENCE ARE HARD TO DETECT

So does a turquoise felt-tip marker make an audible difference?

        USA TODAY set up a simple test.  Using four identical pairs of 
        CDs, we painted the rims of one of each pair.

        As a control, we left one pair untreated.  Theoretically, close
        listening should reveal differences in the other pairs, but no
        difference in this pair.

        The four CDs, recommended by people who have listened and
        heard differences:

          > _Jazz_, Ry Cooder (Warner Bros.).

          > _Face Value_, Phil Collins (Atlantic).

          > _Mussorgsky: Pictures at an Exhibition_, Jean Guillou,
            organ (Dorian).

          > Any version of _Pachelbel's Canon_ (our choice: the 
            version with Andrew Parrot and the Taverner Players,
            on EMI).

        Then we asked five people to listen, without telling them which
        was which.  And we found that, where perceptions are involved,
        nothing is as simple as it seems.

        Two listeners heard no differences; three said the difference
        was dramatic.

        But, among those three, the turquoise ring's effect was preferred
        only 22 percent of the time, while the unringed sound was 
        preferred 56 percent of the time.  And two of the three heard
        a difference in the unringed pair as well.

        Only one listener consistently preferred the turquoise ring's
        sound -- and could tell which pair was unmarked.

        Does this mean there's no difference?  That the marker harms
        the sound?  That people hear what they expect to hear?  Or 
        only that some people hear more than others do?

        The bottom line is, if it makes a difference to you, it works.
        And the only way you'll know is to experiment for yourself on
        a disc or two.

        But be careful.  The marker's solvent obviously does its work
        well.  The edges of the CD feel rougher, almost tacky.  And
        the color penetrates the plastic.

        The larger question:  Is it wise to turquoise-up an entire CD
        collection?  Long term, the marker could possibly eat into the
        plastic enough to ruin a CD.  That's quite an expense to put on
        the line for a modest improvement -- or no improvement at all.

        It might be wise to wait for mass-market markers specifically
        designed for use on discs.  The first:  CD Stoplight, from
        AudioPrism in Issaquah, Wash., expected in audio stores this
        month for $14.95.  It should be gentler to your CDs; at least
        you'll have someone other than yourself to blame if it isn't.

That's all I've got. When I get a minute, I'll type up the rest of the article and put it in the archives, but I make no promises on how soon that will be.

Emily "that was 1990--I wonder how many of the enthusiasts

in the article still paint their CDs green now?" Kelly