Naff Movie into 'DVD Spectra'

Step 5 Constructing the wedge

Take the two triangular pieces and join them to the main rectangular piece using sticky tape on the 'inside' of the wedge. You should then be able to test it out by positioning the wedge along the inside edge of the DVD case, and closing the case lid. This should form a nice robust edge shape approximately 30^o thick. Trim the parts as necessary to provide a snug fit.

Once you are happy with the fit, take some stickytape and wrap a little around the left and right edges of the square slit hole. This is to ensure a crisp edge to your slit, rather than having the card fibres visible in the eventual spectrum.

Fix the two blades on the inside of the slit hole in your 'wedge', lined up with the line you scored earlier. The closer you get the blades, the finer the lines in the spectrum you eventually see. However if the blades are too close little light gets through and its difficult to see anything. A hair's breadth apart seems about right.

Alternatively, if you don't want to fix razor blades inside your 'DVD Spectra' (say you are going to let your kids have access to it) you can make the slit out of a plastic lid. Just cut an even slit in a section of plastic from the lid, longer than the hole, and fit the plastic over the hole in place of the blades. Its not as good as evenly spaced blades, but the plastic ensures a crisp edge and with care you can make it even. Cardboard or paper won't work, the fibres along the cut edge get imaged into the spectrum you see.