or, How to Destroy CDs and similar media
Method:
We've all heard about how it's possible to put a compact disc into a microwave oven and destroy it. In the process, it also makes a lot of sparks. My method was to put a CD into the microwave (700 watt model) on top of a paper towel for around 12 seconds. You may need to adjust the microwave time down somewhat for more powerful microwave ovens. It is quite smelly, but appears to cause no real damage. Since I'm not sure what fumes are released, I recommend opening a window afterwards. Unfortunately, I was never able to catch the sparks on camera, but if you leave it in long enough, eventually the cd will get hot enough to start on fire. The second image is just an image manipulation of the first.
If you do it properly, then when the microwave goes off at 12 seconds, there will be a lot of spark-marks (where the arcing has vaporized the thin layer of aluminum) but very little burning. You can get some really amazing patterns. Here are those I've tried so far, along with the brand of cdr or whatever it was that was zapped to produce it. (By the way, I used the Retinex filter, which is built into The Gimp, an excellent free software image editing application to fix the mistakes my camera makes with color selection. It's under Filters->Colors->Retinex and I always use the "High" level. This filter is slow for large images, but the results are impressive.)
Results:
An actual CD, not a CDR, that had the soundtrack to a videogame I bought. I've no idea why they included the soundtrack, but it sucked. Makes a neat-looking pattern now though.
This is another actual CD, this one to an absolutely useless piece of software included with an ordinary piece of hardware I bought. Not as much fun of a pattern on this one.
An old-fashioned Dysan 650mb CDR with the thick lacquer layer on top of the aluminum. This has some square arcing pattern, along with substantial melting between zones.
This is a modern "Hypermedia" branded CDR with just the colorized aluminum layer on the back. Note the near-square arc pattern.
This is a modern "Imation" brand CDR with the colorized aluminum backing layer. This looked almost identical to the "Hypermedia" one above before microwaving, (save the brand name, of course) but has a completely different arc pattern. Note the small subsidiary arc points in addition to the primaries.
This is a modern "Verbatim" brand CDR with the colorized aluminum back layer. This looks similar to the "Hypermedia" brand's burn pattern, and I suspect that if I'd left them in precisely the same amount of time, they'd be even closer to the same.
This is a "Verbatim" branded DVD+R, with no plastic label on the back. (It was purple before microwaving too.) Up close, this appears to have some of the same primary and subsidiary arcing pattern that the "Imation" CDR did. Additionally, there is bubbling between the plastic layers (DVDs have two layers of plastic, with the reflective aluminum between rather than the single layer for a CD). Another interesting phenomenon is that there are several widely spaced and very compact bubble points, indicating that those points melted without the surrounding plastic doing the same.
This set of discs is where I tried an unusual experiment. The idea is that people sometimes use (or try to use) microwaves to destroy data on CDs. Seeing as how CDs are seen as relatively small data storage these days, I figured that folks who want to destroy one CD might prefer to destroy many. With this in mind, I tried microwaving a stack of 4 CDs on top of one another. The order you see above is the stacking order, from top to bottom. I left this stack in for over 30 seconds. Note how most regions of most discs are completely undamaged, while a small area on the right of each disc is more severely damaged. What happened is that most of the disc surface stopped arcing, while that one area started to melt through the whole way. The result was the nastiest of the discs I burned above, with the melted discs sticking together badly and smelling horrible. As the melted plastic cooled, it tended to form long sticky strands, the result of which is the plastic stringy stuff going off to the right of the images.
Conclusion:
As a method of destoying the data on a CD, microwaving has often been criticized as flashy but ineffective. While this may be true if the microwaving is used poorly, I feel that the conclusion is too quick. Remember that for a CDR, the data is stored, not in the reflective layer itself, but in the discoloration of the plastic immediately adjacent to that layer. This means that if you carefully flake off the reflective aluminum, and then apply another layer (with the grooves properly placed) it would probably be possible to read the data off again.
Microwaving a single CD mostly attacks the aluminum layer. This is relatively ineffective, as can be seen by the large regions of un-zapped material in between the zapped parts. If you simply want to make the data unrecoverable, as opposed to impossible to figure out what it was, then it might be adequate. For proper data destruction, however, the plastic is what should be attacked. To this end, I found the microwaving of multiple CDRs in a stack method surprisingly successful. In only 30 seconds, large areas of the CDs were melted. If one were willing to wait a few more seconds, the majority of the CD would have been melted. This should be an effective method of destroying data, if one can stand the stink and the smoke which would be produced.
Alternatively, any method which melts the plastic of the CDR should be adequate. I recommend a campfire (stand upwind).
As a method of destoying the data on a CD, microwaving has often been criticized as flashy but ineffective. While this may be true if the microwaving is used poorly, I feel that the conclusion is too quick. Remember that for a CDR, the data is stored, not in the reflective layer itself, but in the discoloration of the plastic immediately adjacent to that layer. This means that if you carefully flake off the reflective aluminum, and then apply another layer (with the grooves properly placed) it would probably be possible to read the data off again.
Microwaving a single CD mostly attacks the aluminum layer. This is relatively ineffective, as can be seen by the large regions of un-zapped material in between the zapped parts. If you simply want to make the data unrecoverable, as opposed to impossible to figure out what it was, then it might be adequate. For proper data destruction, however, the plastic is what should be attacked. To this end, I found the microwaving of multiple CDRs in a stack method surprisingly successful. In only 30 seconds, large areas of the CDs were melted. If one were willing to wait a few more seconds, the majority of the CD would have been melted. This should be an effective method of destroying data, if one can stand the stink and the smoke which would be produced.
Alternatively, any method which melts the plastic of the CDR should be adequate. I recommend a campfire (stand upwind).
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