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1: Which side of the CD-R is more sensitive?

The printed one. Underneath this there is an extremely thin coating - where the actual storing layer of the CD-R - the dye - is positioned (you should avoid exposure to sunlight and extreme hot and cold conditions). An additional protective layer containing fine ceramic particles makes the EMTEC Ceram Guard highly resistant and protects the sensitive reflective and recording layers against damage.

2: From which side is the CD-R written to?

From the unprinted side (generally appears silver, blue or green)

3: What causes the protective coating to come off sometimes?

Tiny areas of damage to the protective layer (coating) over the memory layer, caused by scratching or chemicals. For this reason, ballpoint pens are totally unsuitable for labelling; care should also be taken with felt pens. An additional protective layer containing fine ceramic particles makes the EMTEC Ceram Guard highly resistant and protects the sensitive reflective and recording layers against damage.

4: How often can a CD-RW be written to?

Up to 1000 times. A CD-RW actually consists of the same layers as a CD-R. The main difference lies in the writing substance: where a CD-R uses an organic dye, the CD-RW uses a completely different writing substance consisting of an alloy of silver, indium, antimony and tellurium, embedded between two auxiliary layers. Writing is carried out by means of phase change (magneto-optical); the laser beam produces two different reflective characteristics in the material (crystalline = high reflectivity, amorphous = low reflectivity), which then create the traditional combination of pits and lands. The state (crystalline or amorphous) is reversible. The reflectivity of the material is considerably less than with a CD-R. The laser wavelength for RW media is 650 nm compared with 780nm for a CD-R: this is why different appliances are needed.

5: What do 1x - 4x, 4x - 10x, 16x and so on mean?

These figures tell you the speed with which the CD-R can be burned. The maximum write speed, however, depends on the speed of the writer. For example: the CD-R is 16x, but the writer can only write at 12x speed - so the CD-R will be burned at a maximum speed of 12x.

6: What is the difference between a CD-R and a CD-RW?

CD-R means CD Recordable, i.e. these disks can only be written to once (with the appropriate CD writer). CD-RW means CD ReWritable, i.e. data that has been saved can be deleted and overwritten. For this a special CD-RW drive is needed, although this has now become standard.

7: Why do 750 MB fit onto an audio CD but only 650 MB onto a data CD?

A sector of a CD consists of 2352 bytes. With an audio CD, these are used completely for audio information. With data CDs, an additional fault correction is inserted, and the usable capacity shrinks to 2048 bytes. A 74 minute CD consists of 74x60x75 = 333000 sectors. With 2048 bytes per sector, this gives a usable capacity of around 650.1 MB, with 2352 bytes per sector it gives around 746.6 MB. This therefore also produces a difference in data rates for reading/writing: 172 kbps with audio and 150 kbps for data.