5.2.5 Marking
Marking and labeling a CD or DVD is an essential process in its creation. CDs and DVDs, or their containers, are labeled in some form or fashion so that they can be identified and organized. When labeling a CD with markers, the composition of the ink in the marker and the style or design of the marker should be considered.
The inks in markers vary in chemical composition and are formed from pigments or dyes, and solvents. Inks are divided into three basic categories according to the type of solvent used: water-based, alcohol-based, and aromatic solvent-based. Within these categories, inks are further divided according to their permanence and their application to different surfaces.
Markers themselves also vary in form: there are fine-point, extra fine-point, rolling-ball, ballpoint, soft felt-tip, and chisel-tip. Some are ideal for CD labeling; others can cause damage.
Numerous CD vendors have noted that the thin protective lacquer coating can deteriorate from contact with certain solvents in markers. To eliminate the risk, water-based markers are recommended for CD labeling. As a solvent, alcohol is generally less damaging than xylene and toluene, which are common in aromatic solvent-based markers. According to anecdotal reports, alcohol- based markers can be used to label CDs without causing performance problems. However, there are no explicit lab test results to show what effect solvents in markers have on different CDs or DVDs, particularly over the long term.
The vulnerability of the metal in CDs, because of its proximity to the surface, should be considered when choosing a marker. The metal is particularly susceptible to damage from scratches, scrapes, or denting caused by surface marking. A felt tip marker will minimize the risk of scratching or denting.
As mentioned before, CDs and DVDs look similar, but their layer structures differ. The recording layer of a CD is located just beneath the labeling side. On a DVD, the recording layer is in the center of the disc. In theory, solvents from a solvent-based marker will not penetrate to the center of a DVD through the polycarbonate layer on both sides of the disc. Consequently, the data and met- al layers in the center, in theory, should not come in contact with any harmful solvents. Nevertheless, the same precautions taken in labeling CDs are advisable for DVDs. The marker used to label a CD will work just as well on a DVD. Restricting oneself to the CD safe marker will also eliminate the potential for mix-ups in the use of distinctive CD or DVD markers.
Many vendors sell CD-safe markers, and they vary in ink solution. They should not contain any solvents harmful to CDs or DVDs but should have a permanent quality. For risk-free labeling of any disc, it is best to mark the clear inner hub or the so-called mirror band of the disc, where there are no data (see Figure 12).
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