When we routinely carry devices holding tens or hundreds of gigabytes of data, it’s sometimes a shock to remember that there was once a time when 650 MB on a CD was a very big deal indeed. These now archaic storage media came first as silver pre-recorded CD-ROMs, then later as recordable CD-Rs. Most people eventually owned CD writer drives, and some fancy ones came with the feature of etching pictures in the unused portions of the disc.
Haven’t got a fancy drive and desire an etched CD-R? No worries, [arduinocelentano] has a solution, in software which writes a disk image for a standard CD writer whose data makes the visible image on the disc.
CD-Rs have a thin layer of phthalate dye sandwiched between the polycarbonate disc and a silvered layer of lacquer. They’re often gold coloured, but the silvering is in fact just aluminium. The data is encoded as a series of pits and lands crested by the laser vapourising small portions of the dye to make holes.
The code creates a data structure of a standard CD-ROM session which doesn’t contain any usable data, instead whose pits and lands are arranged to form the image. You can find it all in a GitHub repository, and have a go at creating your own offerings. We would have made a Wrencher disc for our pictures, but sadly for some of us who were once in the thick of it we don’t have any CD-Rs any more.