Controversy exists about the use of marking pens, and the answer depends both on the application and on the specific media. Of course, write only on the label side, never on the readout surface. Do not write using a ballpoint pen or other object having a hard point. Discs have a soft, very thin protective coating on the label surface that is vulnerable to chemical or physical attack. The safest method of identification is to rely on the manufacturer's lot code that is present on the clear inner ring of the disc. Small, custom markings in this area can be safely made with felt-tipped marking pens that use water-based inks. Such pens may be available from CD-R manufacturers, or the Dixon Redisharp Plus! can be purchased at office supply shops.
Popular felt-tipped pens, such as the Sharpie, use solvent-based inks. The solvent can attack certain DVD protective coatings, causing degradation that may not be immediately apparent. Even water-based inks may not be safe, since the permanent ink from any marking pen can subsequently degrade the information layer. Predictions of longevity for discs containing label-area markings is difficult because of many variations in the manufacture of these discs. Various dye types and metalizations may interact differently with markers. Protective layers were initially solvent-based, but UV curable coatings are used more frequently because cure times are shorter. Resistance to solvents and inks of each coating type can differ. Discs having various types of hard overcoats and printable surfaces are available, some of which offer additional protection while others do not, or may even degrade longevity.
Bottom line: Pens containing solvent-based inks may be satisfactory with some discs, but water-based inks are always safer.
Last update: 07:18 PM Wednesday, December 5, 2007