Posted on Saturday, September 27, 2003 - 10:57 am:

Please pass this along to others in your department before it happens to you.

CDs, CD-Rs and similar media record and read data from the aluminum layer by reading through the clear plastic diskette. The aluminum data layer is underneath the printed or paper label on the “face” or top of the CD. When you process CDs, DO NOT USE LIFTING TAPE on the label side! The tape will often lift the aluminum layer (which contains the recorded data) and the information is thus destroyed.

Here is an image of what will happen. The disk is clear where the aluminum layer was lifted (click to enlarge):

You should also be aware that some adhesive labels and some inks may slightly dissolve or otherwise damage the aluminum layer, even if you do not remove (lift) the label. Sharpies are usually okay, but ball point pens can damage the CD and when possible it is best to use markers manufactured especially for marking CDs.

If you place an adhesive label (such as an adhesive evidence tag) on a CD and it begins to lift or peel away, you can lose the information that is on the CD.

Computer crime units can resurrect some information from damaged CDs (and even from some floppy diskettes cut into pie-slice pieces with scissors), but the procedure is very time consuming and usually some data (sometimes all data) is lost (see http://www.usdoj.gov/usao/eousa/ole/wbt_7advdatarec.pdf). To destroy classified data on CDs, the federal government uses commercial grinders (which make a horrible noise) while grinding/rasping away the label side of the CD to leave a translucent (because it is scratched) plastic diskette.

Jeri Eaton
King County Sheriff’s Office
Seattle, WA

Related links:
www.osta.org/technology/cdqa11.htm
www.cdrfaq.org/faq07.html#S7-20
www.synthemedia.com/mtc/mtcframeOVR.html
www.cliffshade.com/dpFWIW/cd-r.htm#labels
www.cliffshade.com/dpFWIW/cd-r.htm