I've been making a hand spectrometer, as outlined on CLEAPSS, with some success. The hardest part of the process is stripping the printed surface off the CD / DVD, so that I can use the transparent disc as my diffraction grating. I've been peeling the print off with duct tape, with patchy results. Does anyone have any tips for a better way to clean off a CD / DVD please? Our physics teacher liked the end result, so I may need to make a class set in the new year... Thanks, Helen.