As it has been already said, the media you are going to use in all situations does not exist. Each one of them works well in specific situations. Let's start by describing the quality of each media according to the price, material and additional features by manufacturer and then see their utilities.

When we mentioned the CDs RW you might have thought that there are different prices for them, since US$ 5.00 up to US$ 30.00. And it is difficult to understand the reason for this whole variation: quality of the material. The cheaper the CD-RW, the shorter its lifetime and use potential, that is, the cheapest CD-RWs are not re-recordable anymore with the passing of time. The crystal that turns transparent or opaque according to the wavelength gradually loses that capacity with the recording/erasing of the CD. The more expensive CDs are made of crystals that involve more technology and will last more. We have tested a CD-RW by Ricoh that cost about US$ 8.00 and it allowed just 2 recordings. Today it is nothing but a regular CD-R! With the disadvantage of not being read in any drive. This 30% refection problem is another one that tends to get worse with time.

Also - and now we are talking about all kinds of CD - the cheaper the CD the worse its quality in all senses. The basic plastic material can go through the same problems we have mentioned and others, such as extreme hardness with time, which makes the CD easily broken or it can even twist it out of shape. This changing in shape can be also caused by the temperature, because the coefficient of thermal dilation of the metallic and recording layer is different from the plastic. Don't you remember any CD-R that started to make noise after some time in the drive? That's it, it happens because the metallic and recording layer dilates less than the plastic layer, making the CD to form a very discrete "U" shape that does not interfere in the reading, but can touch some part of the drive or even make noise while moving the air around it.

The color of the media can give us a hint of the use we can give a CD. The green dye media, for instance, was initially made of cyanine over gold. But the concentration of that cyanine is much lower than the one in a blue CD, for example. That makes this kind of CD skip tracks easily when used to record music, because it has lower recording surface density and is more reflective. If the laser beam does not touch exactly the recording track, that is much less dense in this case, the CD will skip tracks.

Nowadays practically all green dye media are made of phythalocyanine over gold. As the phythalocyanine is less bluish than the cyanine, the concentration of this material has to be much higher to result a dark green color, reducing the reflexivity and increasing the recording surface density, that makes the recording tracks denser and makes the CD skip less tracks.

When the phythalocyanine was released, the specialists ventured a supposition that the cyanine reacted with the gold, what has not been denied by the industry. That makes the CD with that combination (the first green CDs) to have a much shorter durability than the present ones. Beside, that kind of media got a bad reputation due to the first green CDs by TDK that did not have a layer against scratches as efficient as it should be, so, any small scratch made the CD to show reading errors.

It is also easy to understand that CDs with lower recording surface density are not ideal for higher speed drives. When a manufacturer recommends the recording and read speed of your CD, it does that based in calculations that involve the density of the recording and reflective material. Choosing a CD according mainly to its recording speed is fundamental when the recording is higher than 8x, also called critical speed.

However, the green media has the advantage of being more flexible to power variations than the others, making it more readable in different drives, mainly the older ones. Still today the TDK media is one of the best in this category.

The gold media and silver media are made of phythalocyanine layers over gold. As any media with gold reflective layer, these two ones have longer durability, because gold lasts more than silver. Another advantage is the fact that they work better in high read and recording speed Another advantage is that they work better in high read and recording speeds than the green ones.

This happens because the phythalocyanine used in those media is colorless and therefore has to be much more concentrated to make the gold reflective layer clearer than the gold natural color. In the silver CDs this reflective layer takes other metals in the alloy that make it less gold, mainly the aluminum that is found in cheaper CDs, but yet have predominantly 24K gold. There are obviously the bad manufacturers, that compensate the color by reducing the concentration of phythalocyanine and also reducing the gold from 24K to 20K, 18K and even 16K! It is the case, for example, of most silver/green CDs sold in Brazil for about US$ 1.00 each. As the addition of silver, copper and other metals in the gold alloy was not enough, they are practically 50% aluminum. Be careful! Besides being the worst in durability, those CDs are the less recommended for audio and read/recording in drives above 8x.