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At 10:28 PM 8/20/2004 +0000, Don Cox wrote: >I cut a sliver off the centre hole and examined it on a lightbox. The >dye is in the plastic - it is definitely black polycarbonate. > >The other colours might be just layers. I haven't seen them. I am sorry - I often make assumptions about the knowledge of my correspondents which are not supported in fact. A write-once disc consists of several layers. from the bottom surface, the one through which it is illuminated, they are: 1. A thick, clear polycarbonate layer 2. A thin polycarbonate layer with light-sensitive dye 3. A metallic overlay which reflects the illumination 4. A thin acrylic lacquer 5. Any overcoating, printing or related surface. The decorative pigment is in the plastic, 1 above. The illumination passes through that layer before passing through 2 on its way to 3; then after passing through 2 a second time. While essentially opaque to visible light, the pigment in 1 is approximately transparent to the infrared illumination. Yes, it appears to be through the polycarbonate since the dye layer is quite thin; in fact, the pigment may also permeate the dye layer, though I believe it does not. Regardless, the dye layer would be extremely hard to see in cross section - it is thin so that it is within the depth of field of the illumination where the pigment is ideally perfectly out of focus. Note the distinction between the light-sensitive dye and the decorative pigment. Mike -- [log in to unmask] http://www.mrichter.com/