All about CDs and CD-Rs Part One
By Matthew Toledo - 10/17/2001
CDs revolutionized the way we listen to and record music and the invention of CD-Rs have extended the revolution to the average Joe. But in any revolution, there is collateral damage. Currently, any singer songwriter or small studio can "burn" their own music to CD-R at a relatively low cost. Unfortunately, any kid with a computer and a CD burner can make unlimited pirate copies of the same disk. CDs and CD-Rs paired with mp3's have shaken the recording industry to it's core with both good and bad effects.
Over the next few months, I plan to write about our pal, the CD-R, and what it can do for you and to you. This month, I'll discuss the difference between the various types of media. For instance, what the heck is the difference between CD-Rs? Is there a difference? Why are they different collors and do CDs sound better compared to a CD-R?
CDs, CD-Rs, and Dyes.
Oh, where to begin? CDs are not the same thing as a CD-R. CD-Rs typically have a shorter life span than CDs and various audio engineering magazines have proven that CDs actually sound better to the trained ear than a CD-R. Why?
CD players works by bouncing a laser off the surface of a compact disk. On a real CD (not a CD-R), there are actual physical pits and lands on the surface of the reflective layer. A CD player works quite like your parent's record player. Except instead of a needle amplifying the peaks and valleys in record groove to make analog sounds, a laser reads a CD for ones (peaks) and zeros (plains) where a computer translates it into digital sounds. The tiny difference in amount of laser light reflected by the pits and plains is what makes a CD tick.
CD-Rs do not have pits and valleys. They use a photo sensitive dye to emulate the physical characteristics of a real CD so they act the similar to a CD when hit by a laser. Since the dye on a CD-R is photo sensitive it can be damaged by sunlight or even the laser used to read it. So if you leave a CD and CD-R face up in the back of your car all afternoon, chances are your CD-R will have been wiped clean while your CD will still play--provided neither of them melted in the hot sun, that is.
CDs may also last longer than CD-Rs, though the technology hasn't been around long enough for anyone to prove it for sure. Rapid aging of CD-R's have shown that. CD-R dyes can decompose over time, or oxidize. The life span varies with your treatment of the disk. Keep it scratch free, dry, and out of the sun and some say a CD-R can live from 70 to 200 years. While CDs can last longer. Wow.
So why use CD-Rs if they are so fragile? Well, my friend, they are cheap. But only to a certain point.
A real CD is literally "replicated" from of an infusion of plastic material into a mold (called a Stamper) which was made from a Glass Master disk which is "etched" with the digital information. The cost of the technology used to make the Glass Master and Stamper is so great that replicating small numbers of discs is very expensive per disk. It doesn't make sense to make just one copy of a CD, or even a hundred copies of a CD. Most CD manufacturing companies usually won't print a CD unless you order 500 copies.
Your most economical bet for duplicating a low number of disks is to make a CD-R, not a CD. Backing up data from your computer to a CD-R, or making a compilation disk for your upcoming road trip is a perfect job for a CD-R. If you own a computer with a CD-R recorder, your only investment is the price of a CD-R, which can be anywhere from 20 cents to a dollar a disk.
All CD-Rs are not the same. Like most things in life, you usually get what you pay for. Cheaper CD-Rs won't play back on some CD Players, or they won't last long, or they won't sound as good. Various companies make a CD-Rs reflective layer from different dyes. That explains why some CD-Rs look silver, or gold, and others look black, green, or blue.
According to the folks at mediamasters.com, "Silver CD-Rs are the premium CD-R in the industry and years of experience tell us that the best CD-Rs are Mitsui Silver." Mitsui's Silver CD will sound as close in quality to a real CD. However, they are pricey costing a dollar per disk. They sound good because they are more sensitive to light and have better reflective properties. While the light sensitivity is good when you burn a disk, it means they won't last as long. Silver CDs will last around 50 years max.
So why do CD-Rs come in different colors? It depends on which dye they use. The following information about dyes comes from http://www.discsdirect.com/
Cyanine: a dye that is blue in color. Combined with a gold reflective layer the CD-R appears green. If a silver reflector is applied, the discs appear light blue in color. A major advantage of Cyanine based discs is that they work with a wider range of laser powers, making them more compatible among several different brands of writers. This is due to the fact that Cyanine has a greater sensitivity to light than other dyes. This characteristic also affects their longevity. These discs have a life span of 50 plus years. The majority of Maxell CD-R media sold in the US is Cyanine based.
Pthalocyanine: This dye is actually yellow-green in color. When combined with a gold reflector the discs appear gold or greenish gold in color. Pthalocyanine dye is a newer dye that has less sensitivity to light. Resulting in a life span of up to 100 years. However, less light sensitivity can sometimes be an issue when it comes to working with certain manufacturer's writers. Maxell CD-R media manufactured in Mexico is Pthalocyanine based.
Azo: Mitsubishi Chemical Company manufactures this dye. Azo discs usually use a silver reflective layer that give the data side of the disc a deep blue color. This dye has been used in other optical recording products in the past. Some early formulations of Azo dyes had difficulty writing at higher speeds. Longevity for Azo based discs should be in the 100-year range.
So what does this all mean. If you want a quality recording that will play on just about and CD or CD-R player, you want a Silver or Cyanine CD. If you are looking to archive data from a computer for a long time, go for Pthalocyanine based CD-Rs. If you want your music to be around after the fall of society. Pay a CD replicating company to print 500 real CDs.
650 MB Vs 700 MB?
CD-Rs come in two sizes. 650 MB CD-Rs were around first. They hold approximately 74 minutes of music or 650 MB of data. 700 MB disks were a more recent invention. They hold 80 minutes of music or about 50 MB more data than the earlier CD-Rs.
Both disks are physically the same size, meaning they both fit in a CD player. The 700 MB disks gain the extra data by make better use of the real-estate on the plastic. The recording surface starts further in towards the center hole than a regular 650 CD.
While more recording time may sound like it's better, some older CD players may not be able to read the 700MB CDs. If you are making a compilation CD for a road trip, and you know for a fact that your old boom box's CD player can handle the larger disk, then go for it. However, if you are in a band around Athens and you want everyone in this town to be able to hear your recording, stick with the 74 minute (650 MB) disks. There are a lot of really old CD players being used in Athens right now. For example, during my brief stint as a DJ for 1340 AM. I noticed that only their newer consumer grade CD player was capable of reliably playing CD-Rs while the older "professional" CD players choked on some CD-Rs.
CD-R Care
CD-Rs have two sides. There is a data side and a label side. The gold or silver and dye material are located underneath the label. It is extremely thin and accounts for about 1/100th of the thickness of a CD. The rest of the plastic is used to refract the laser light a certain way and to protect the thin data layer.
Never write on a CD-R or CD with a ball point pen. You can damage the thin data layer easily. Likewise, some permanent markers may seep through a CDs label or plastic and damage the data layer. You'll have to use trial and error to find out which markers not to use. I always use a black Sharpie brand marker and have had no problems to date.
Never leave your CD-R exposed to sunlight. Ultraviolet rays will commit some ultra-violence to your data. Put the CD-R back in it's case and away from the sun.
Try not to handle a CD-R too much. Always hold it by the edges or center hole. Don't get your finger prints on it or it may cause your CDs laser to reflect early or refract a different way. Unfortunately, wiping a CD is a bad thing to do as well. If you do have to wipe, use a slightly damp, high quality cotton cloth to wipe from the center of the disk to the edge. Use high quality cotton because it leaves less lint.
Finally, and this is a no brainier, don't write on the DATA side of a CD-R. The ink will block your CD player's laser making the data illegible. If you buy blank CD-Rs that don't have a label, it is sometimes it is hard to tell which side of a CD-R is which.
In Conclusion...
So, to recap. CD-Rs mimic CDs by manipulating the amount of light reflected by a CD player's laser. Silver based CDs sounds better, in particular, Mitsui's Silver CD. If you want everyone to be able to hear your CD-R, use a 74 minute one. And lastly, don't bitch-slap your CD-Rs. Treat them right and they will last for decades.
One footnote. Philips makes a proprietary CD and CD recorder. Perhaps you've seen the commercials on TV. You know, the commercial with the dancing pets or the hot chick listening to some guys "Love Mix" over dinner. Unfortunately, Philips CDs don't work well with other burners and don't play on all CD players. So if you are looking to mass produce your band's new disk, stay away from Phillips.
Next Month... burners and burning software.
