A degausser is a device that uses a strong magnetic field to remove data stored on magnetic storage media like hard disk drives, floppy disks, and magnetic tape. But can a degausser also erase the data on optical media like CDs, DVDs, and Blu-ray discs? Let’s take a closer look at how degaussers work and whether they can effectively erase optical discs.
How do degaussers work?
Degaussers create a powerful, alternating magnetic field that rearranges the orientation of magnetic particles on a storage medium. This renders the existing data unreadable and writable. Hard disks and magnetic tapes store data using tiny magnetic grains layered on an aluminum, glass, or plastic platter. A degausser essentially scrambles these magnetic bits into a random pattern, making the original data inaccessible.
Degaussers are able to generate magnetic fields ranging from 5000 to 20,000 Oersted depending on the model. For reference, the Earth’s magnetic field is around 0.5 Oersted. This strong pulsating field can penetrate the protective casing of hard drives and magnetic tapes to reach the magnetic media inside and degauss the contents.
Why degaussers don’t work on optical media
Optical discs like CDs, DVDs, and Blu-rays store data very differently than magnetic media. Instead of changing magnetic polarity, optical media store information in microscopic pits arranged in a long, tight spiral track on one side of the polycarbonate disc.
A laser beam precisely burns these tiny indentations into the dye or phase change layer underneath the protective plastic coating as the disc spins. The presence or absence of these pits translates to the 1s and 0s that make up digital data. During reading, a lower-power laser beam detects the reflective differences between pits and untouched spaces.
So in essence, the data on optical discs is structurally engraved onto the discs during burning. Degaussing creates magnetic fields that can disturb magnetically-encoded information, but has no effect on the physical engravings on optical media. The pits and spaces will remain intact despite exposure to even the most powerful degaussing magnetic fields.
Other options for securely erasing optical discs
Since degaussers don’t work on CDs, DVDs, or Blu-rays, what are the options for completely erasing data from optical media? Here are a few effective methods:
Physically destroy the discs
The most direct way to make sure no data can ever be retrieved from an optical disc is to physically break it into small pieces. Methods like shredding, crushing, or snapping a disc will damage the recording layer irreparably beyond any chance of data recovery. Unlike magnetic platters, the data is embedded into the disc structure, so physical destruction is very effective.
Use an optical disc shredder
Specialized optical disc shredders, disintegrator, or pulverizers can obliterate CDs, DVDs, and Blu-rays while capturing the resulting debris. These machines shred the discs into tiny particles that are usually too small to piece together meaningfully. Optical disc shredders provide fast, convenient, and reliable physical destruction.
Use disc destroying software
Software like Disk Doctors Optical Media Erasure can “shred” an optical disc by repeatedly writing random data until the disc surface is too damaged for previous files to be read. However, data could theoretically be recovered if the erasure is interrupted prematurely. So combining disc destroying software with physical destruction is most secure.
Use an optical disc sander
Sanding machines designed for optical media use coarse abrasives to grind away the label side of a disc, destroying the reflective data layer underneath. This method permanently removes stored data and makes the disc unreadable. However, tiny data remnants could remain between tracks, so combining sanding with physical destruction enhances security.
Expose to high heat
Optical discs start becoming unreadable above 140°F as the reflective layer breaks down. Exposing CDs, DVDs, or Blu-rays to very high heat from fire, incineration, or microwaving can damage the data encoding layer enough to prevent data recovery. But the platters might remain somewhat intact, so combining heat with mechanical destruction is ideal.
Best practices for securely erasing optical media
Here are some key tips for completely obliterating data from optical discs:
- Use physical destruction as the most reliable method. Optical shredders provide fast destruction.
- Heat and abrasion alone might not completely destroy recoverable data remnants.
- Combine degaussing with physical destruction to erase magnetic and optical media.
- Remove any disc fragments and particles after destroying to prevent reassembly.
- Destroy the discs to small pieces under 2-3 mm for highest security.
- Use multiple passes for overwriting, sanding, or shredding for greater assurance.
- Check resulting debris to verify no large sections remain intact.
Can you reuse an erased optical disc?
After degaussing, destroying, sanding, or overwriting an optical disc, the media is no longer reliably readable or writable. The physical damage is too great to reuse the discs. However, some discs might seem visually intact after data destruction. It’s important to still properly dispose of those discs so the platters don’t fall into the wrong hands.
For safe recycling or disposal, completely deface the shiny data side of the disc with permanent markers before tossing the disc in the rubbish bin. This step also makes it obvious the disc is destroyed and prevents accidentally reusing it later on.
Conclusion
While degaussers are excellent for erasing magnetic media like hard drives, they are ineffective at removing data from optical discs like CDs and DVDs. The physical engravings that encode the binary data on optical media are immune to magnetic degaussing fields. Physically destroying the disc using shredding, abrasion, or heat provides the only sure-fire way to make the data irretrievable.
To permanently erase optical discs, using a combination of degaussing, physical destruction, and defacement is ideal. Degaussing covers magnetic media, while shredding, sanding, or incinerating prevents optical disc data recovery. Following up with recycling or secure disposal ensures no data remnants remain. Implementing a layered, redundant data destruction process is key to properly retiring optical media.
| Method | Effectiveness for Optical Discs |
|---|---|
| Degaussing | Not effective, optical discs use physical engravings not magnetic encoding |
| Physical destruction | Very effective, shreds/breaks disc platters beyond recovery |
| Abrasion/sanding | Largely effective, but some data remnants may remain |
| Exposure to heat | Largely effective, but some data remnants may remain |
| Overwriting software | Ineffective alone, must damage platter surface to work |
