I transfer old reel-to-reel audio tapes for clients to digital. Finding the “best” CD-R medium has been difficult. It needs to last 100 years and have a low bit error rate. Who make the best?

First, any CD-R will last longer if stored correctly. In general, if you are comfortable, the disk will e also. Avoid high temps, humidity and light. Recommended Storage conditions are as follows :
Temperature Range: 5C to 30C
Absolute Humidity: 1 to 20 grams/cubic meter
Relative Humidity: 8% to 50% *dew should be avoided

For archiving:
Discs should be stored vertically in a protective case. (A standard jewel case is adequate. In jewel cases,
the disc is suspended by the center hole and isolates the written area [read side] from contacting any
surface, It also offers some protection against rapid temperature changes). The most likely cause of damage to R discs from direct sunlight is by heat buildup in the disc affecting the dye. Much of the ultraviolet range of sunlight can be filtered (or absorbed) by glass—e.g., the glass of a window. However, the lower light frequency (infrared) range will pass through a window and generate heat in the disc.

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.

There are 16 factories around the world that make CD-Rs. Only one is still in operation in Japan.

Great price and great performance don’t go together. The cheaper disks should not be used for archive.

How are the disks made? The first step in producing a CD-R disc is to create the polycarbonate plastic substrate using an injection molding process. The dye layer is applied using spin coating and the reflective layer by means of cold planar magnetron sputtering. The lacquer overcoat is then applied by another spin coating procedure followed by ultraviolet curing. Additional durability or printable layers are typically applied using screen printing methods. With over 1,000 brands and models of CD-Rs, it’s impossible to fine the best one. The rating would probably change on a daily basis.

That’s the problem with all the reviews I have seen. Writing to a disk does not mean it will last for a long time. I’d suggest that a review written a few years ago is worthless since the manufacturer could have changed the formulation. Having someone saying they got the disks on sale and they burned successfully is not a review and certainly means nothing as far as longevity.
Gold Disk
The longest projected life is 300 years from MAM-A, a subsidiary of Computer Support Italcard (CSI) of Milan Italy from their plant in Colorado Springs, CO. The MAM GOLD discs uses Mitsui Chemical’s patented dye and has a characteristic gold color.

The recording layer of a CD-R disc is composed of one of cyanine, phthalocyanine or azo dye. Some even use a gold layer. Information is written to a CD-R disc by means of a laser to heat and alter the dye sufficient to create a pattern of marks and thereby mimic the pits of a molded CD.

So how do you determine if the disk was recorded properly. One way is to use the verification routine that comes with the burning software. It will compare the just-written disk to the original file. You could then play the disk on another player to make sure the disk is compatible with more than one player.

The manufacturers claim 75 years (cyanine dye, used in “green” discs), 100 years (phthalocyanine dye, used in “gold” discs), or even 200 years (“advanced” phthalocyanine dye, used in “platinum” discs) once the disc has been written. The shelf life of an unrecorded disc has been estimated at between 5 and 10 years. There is no standard agreed-upon way to test discs for lifetime viability. Accelerated aging tests have been done, but they may not provide a meaningful analogue to real-world aging.

Brands most often recommended: Matsui, Kodak, Taiyo Yuden, and TDK. Sometimes Pioneer and Ricoh. It appears that HP, Philips, Sony, Yamaha, and Fuji use these manufacturers for most of their disks. (Kodak no longer manufactures media.)

Brands that are often trashed: Maxell, Verbatim, Memorex, Ritek, Hotan, Princo, Gigastorage, Lead Data, Fornet, CMC Magnetics. Many “no-name” bulk CD-Rs are one of these brands.

Sometimes company names change. For example, in June 2003 Mitsui Advanced Media was purchased from Mitsui Chemicals by Computer Support Italcard (CSI) of Italy to form MAM-A, Inc.

Thanks to http://www.osta.org/osta/index.htm