CDs have already been evaluated on this site as a poor alternative to a true signal mirror. The do reflect a ltlle, but not that well. Commercial CDs are actually pressed from above using a glass die. The die pokes tiny holes in the surface through the reflective coating. This is then covered with the silk screen label, sealing the openings. (This is why you should be careful not to scratch the label of your CDs.<br><br>CDs created by CD-R or CD-RW drives in your PC are created by a laser that burns the tiny holes or pits in the surface.<br><br>Both techniques produce a surface that diffuses the light rather than reflect it. That's how the discks are read by the computer. If the laser beam that's aimed at the CD reflects back from the surface, it's read as a "1" or "on." If it's refracted and is not read by the sensor, it's a "0" or "off."<br><br>They do reflect light, so they will work when nothing else is available. But I'd recommend that you and your scouts look for another material to replace them. <br><br>