Friday, August 14, 2009

Geeks Weigh In: Can You Fix A Scratch...

Excerpted from my daily RSS feeds this one From the folks at make use of dot com :

Geeks Weigh In: Can You Fix A Scratched CD With Toothpaste?

Posted: 13 Aug 2009 03:01 PM PDT

toothpastecdWhenever there’s any sort of topic where the general population doesn’t have a solid understanding of the technology at hand, urban legends are born. You’re probably familiar with such exaggerated stories – like the one where water boiled in the microwave can explode (only partially true), or the one about the Microsoft email beta test where Bill Gates is sharing his fortune with people who forward the email (people actually bought that story?) – in each case people believed the story because they had very little understanding of the underlying technology.

Varun wrote an article a while back on how to repair damaged CDs and briefly mentioned using toothpaste.  In this article, I’m going to take a closer look at the claim that even when many store-bought CD-repair products fail, you can fix a scratched CD with toothpaste.

True or False: Can You Fix a Scratched CD With Toothpaste?

Taken at face value, the claim seems very odd and very likely false. How could smearing a paste on the surface of your CD save the data that lies within? Why not just dip your CD in ketchup, jelly or dish soap for that matter? The truth about the toothpaste claim comes out when you take a look at how a CD actually works. Please examine my poorly drawn sketch of a cross section of a standard CD.

fix a scratched cd with toothpaste

Each of the major layers of a typical CD are displayed here. When you flip over a CD and hold it up to the light to look for a scratch, what you’re looking at is the “thick” polycarbonate plastic layer. I put the word thick in quotes, because we’re talking 1.2 mm here.

Now, if you follow the path of the laser beam through the clear plastic layer, you’ll see that it strikes the aluminum (or reflective) layer. This layer bounces the light directly back to the CD reader. As the CD spins, the time it takes for the light to reflect and return tells your CD ROM whether or not there’s a “pit” or “land” – the structure within the CD where the data is encoded.

fix scratched cd toothpaste

The technology within your CD/DVD drive is actually very impressive considering that the process where the laser from your drive “reads” this structure is very precise.  When the outer surface of the polycarbonate layer is nice and smooth, this process works slick – and your music or video game runs like a champ. However, what happens when there’s a significant scratch on the outer surface of the polycarbonate layer?

home cd repair

As the CD spins and the laser is busy scanning the pit data pattern along each track and decoding the information, when it hits a significant scratch in the polycarbonate surface, the laser beam is deflected just enough so that the pit data pattern is misread.

Now, normally for very small or occasional scratches, this isn’t a huge deal because the data on the CD and the CD drive circuitry has an integrated error-checking code system to handle the occasional misread bit here and there. However, when the scratch is significant enough so that the laser beam misreads a large batch of the track, the disk either skips or becomes unreadable.

Toothpaste To The Rescue – A Minty Fresh CD Repair

A lot of people testify that rubbing toothpaste (either with a soft cloth or a cotton swab) along the scratch has the ability to correct the problem described above. Does this really work, and if so – why? The answer is: Yes. It works, and it works well.

First, when you place a dab of toothpaste on the scratch (preferably baking soda or other “gritty” paste, not gel) and rub the paste into the scratch from the center of the CD outward, you are essentially “sanding” down the imperfection on the surface of the polycarbonate plastic layer. By sanding away the imperfection, you’re removing deflection of the laser beam, and by doing so you’re correcting the problem. Of course, before you attempt to do a “toothpaste buff,” always make sure to wash off any dust and fingerprints from the surface of the CD.

home cd repair

Dry it off with a soft cloth, and always wipe the CD starting from the center and outward toward the outer edge of the CD. This will reduce the chance that you’ll introduce any additional scratches across multiple tracks. Once the CD is clean and dry, you’re ready to buff the surface with toothpaste.

Apply a dab of paste (not gel) to a cotton swab or soft cloth and apply it directly to the scratch. Rub the toothpaste in small circles (like you’re buffing a car) along the length of the scratch. This goes against everything your mother ever told you about not touching the back of a CD – but trust me, you’re doing the right thing.

cd repair

After a while, you’ll notice that while you’ve created some very fine surface scratches, the deeper scratch has either grown faint or entirely disappeared. Don’t apply too much force when you’re “sanding” the scratch – a gentle circular motion is all you need to buff it away. When you’re satisfied that the scratch is either gone or reduced enough to make a difference, put the CD through another gentle rinse and dry.

Congratulations – you’ve just proven that yes, it is possible to fix a scratched CD with toothpaste! If it doesn’t work for you, then follow Karl’s advice on how to read the data off of your scratched disk.

Have you ever attempted the toothpaste CD repair, or do you have any tips and tricks of your own to fix scratches on a CD? Share your insights with MakeUseOf readers in the comments section below.

Image Credit : Gustavo

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