01.CD/DVD repair kits
Optical discs, such as CDs and DVDs, are fairly fragile and it doesn’t take much damage for them to skip or not play. Grease, dust, exposure to excess heat, and rough handling can all result in damage that may affect playback.
Most of us have a large collection of CDs and DVDs. And with so much precious material stored on these discs, repair kits may seem like a way to fix a disc that has been damaged. But do these kits actually work?
To answer this question, we tried different types of use-at-home CD/DVD repair kits (priced between $5 and $80) to see if they could repair damaged discs. Two types of kit were included: abrasive and filler kits. We also rated a retail disc repair service and a popular fine-grain liquid polish to see which method works best.
Please note: this information was current as of May 2008 but is still a useful guide to today's market.
Types of repair kit
There are two different types of disc repair kits — abrasives and fillers.
- Abrasive repair kits use polishes to remove minor scratches from the surface of the disc. The kits include a paste or liquid that contains very fine particles that act like a cutting polish. They aim to polish the outer surface so that the laser can see the tracks on the disc more easily.
- Filler repair kits contain a solution that is meant to fill the scratches on the outer layer of the disc.
The disc repair kits require either manual or machine application. The manual kits contain a cloth and paste. The paste is applied to the disc by hand and then the cloth is used to rub the paste over the scratch. The process can be tiring and many of the pastes are poisonous, so it’s advisable to use gloves and wash hands afterwards.
The machine kits still require you to apply the paste and use an automatic or manual cleaning unit with internal pads that rub the paste into the disc. The automatic, rather than hand-spun, units tend to be less tiring, but you do need to change the pads to get different grades of buffing which can be a fiddly task.
About our test
For performance, we took commercially available CDs and DVDs, scratched them with fine grain sandpaper parallel with the tracks at the start of the disc, and checked that they didn’t play properly. We then applied the products to the scratched discs and subjectively assessed whether they had improved in the damaged area and repeated the application if no improvement could be measured. We also assessed the instructions and ease of use for each product.
The disc repair kits we reviewed all claim to remove scratches and repair discs. However, we found that while these kits can sometimes remove superficial damage, they’re unlikely to be able to repair discs with deep scratches and restore them to original condition. None of the kits were able to restore our damaged discs to their full playback state, although some improved the quality marginally.
The top two for performance were the machines — perhaps because they provide more consistency than manual application. The filler repair kit was not as good as the best abrasive kits.
The liquid polish rated similarly to the filler-type product for performance. The retail disc cleaning service was only rated for performance and performed relatively poorly. Each disc was cleaned twice by the service but there was no improvement in playback.
Cross-section of a CD
A CD consists of polycarbonate (plastic) with tiny pits and bumps in a single, continuous spiral 'track'. A thin reflective layer of aluminium covers the bumps followed by an acrylic layer and then the label.
The read laser passes through the polycarbonate underside of the disc to the reflective aluminium layer underneath, reflecting the laser light from the pits and bumps — which represent the binary data on the disc. Note that recordable CDs use a different structure with a 'dye' that can be changed by a laser, thus allowing tracks to be burned on a disc.
Cross-section of a DVD
DVDs are made with some of the same materials and manufacturing methods as CDs, with the exception that DVDs can contain multiple layers and the pits and bumps are both smaller and spaced closer together.
In additon to a primary reflective layer, a secondary and partially reflective layer allows laser light to either reflect back the pits and bumps on one layer, or pass through to the next reflective layer underneath. When reading, the DVD laser is tuned to focus on one or other of the layers.
Kevin Bradley, Director of Sound Preservation at the National Library of Australia in Canberra, has written on the subject of disc quality. His advice:
"It is preferable that optical discs aren’t repaired or polished as these processes irreversibly alter the disc itself. However, if the disc surface has scratches that produce high-level errors, repairs may be useful to return the disc to a playable state to transfer the data. To most end users, a CD or DVD reaches the end of its life when the drive no longer reproduces the data written on the disc, but because drives are not governed by standards, a CD or DVD that will not play on one drive may well play on another."
Don’t spend your money on a disc repair kit. Instead, use a cloth and an isopropyl alcohol solution to clean the surface of the disc to remove any dirt, grime or grease that may be stuck to it. To do this, use a soft microfibre or lint-free cloth that will remove smears, marks and fingerprints without damaging the actual disc.
And, of course, it’s always better to be safe than sorry so if you have important or irreplaceable files be sure to burn a backup copy of the disc for safekeeping.
If you do decide to buy a disc repair kit, always check if there’s a use by date because the liquids and pastes can dry up and be unusable if left on the shelf for too long.
Protect your discs
Don’t rely on repair kits to fix your discs. Follow these tips to ensure your discs don’t get damaged or scratched.
- Always hold discs by the outside edge.
- Create a backup copy of discs.
- Keeps discs away from moisture and ultraviolet light.
- Store discs individually in an upright position.
- Don’t stack discs or pack them in groups.
- Copy your files to newer formats of discs periodically.
- Use standard data formats that can be read by many software programs.
- Try using the disc in another drive if it gives an error, as some drives handle damaged discs better than others.