Gene Kearns wrote in message
...
On Tue, 24 Oct 2006 12:19:51 -0400, "Eisboch" wrote:


"Calif Bill" wrote in message
thlink.net...



Burned CD's can change. The reason being the construction. The
critical
part of a CD is not the clear side but the shiny side. A pressed CD has
the dimples pressed in and then the coating is applied, and the distance
from the surface to the reflective coating does not change. A burned
CD,
diffuses an internal material. If heat and chemistry happen, that
diffusion can grow or change. The reason a CD works is the light source
is reflected from the shiny coating or the diffused internal area. The
diffused or dimple is 1/2 wave length in depth, so you get a
cancellation
of light. A dark spot. If there is damage to the reflective surface,
then bad data.



I read at some point in time:

A burned CD has an approximate storage life of only 3 years before it can
start having data errors simply due to aging. They are not recommended
for
long term storage of important documents or files.

Interestingly, magnetic media (tapes) have an estimated data storage life
of
approximately 100 years.

Eisboch


http://www.scienceagogo.com/news/200...runc_sys.shtml


I think they are talking about commercial originals. The ones you create on
your CD or DVD burner on your computer (CD-R, DVD-RW) are the ones that have
a much shorter data storage life, according to what I read. I have some
homemade CDs that are a few years old though .... and they still work. I
think ..... (haven't used them in a while)

Eisboch

Eisboch wrote:
Gene Kearns wrote in message
...
On Tue, 24 Oct 2006 12:19:51 -0400, "Eisboch" wrote:


"Calif Bill" wrote in message
thlink.net...



Burned CD's can change. The reason being the construction. The
critical
part of a CD is not the clear side but the shiny side. A pressed CD has
the dimples pressed in and then the coating is applied, and the distance
from the surface to the reflective coating does not change. A burned
CD,
diffuses an internal material. If heat and chemistry happen, that
diffusion can grow or change. The reason a CD works is the light source
is reflected from the shiny coating or the diffused internal area. The
diffused or dimple is 1/2 wave length in depth, so you get a
cancellation
of light. A dark spot. If there is damage to the reflective surface,
then bad data.



I read at some point in time:

A burned CD has an approximate storage life of only 3 years before it can
start having data errors simply due to aging. They are not recommended
for
long term storage of important documents or files.

Interestingly, magnetic media (tapes) have an estimated data storage life
of
approximately 100 years.

Eisboch


http://www.scienceagogo.com/news/200...runc_sys.shtml


I think they are talking about commercial originals. The ones you create on
your CD or DVD burner on your computer (CD-R, DVD-RW) are the ones that have
a much shorter data storage life, according to what I read. I have some
homemade CDs that are a few years old though .... and they still work. I
think ..... (haven't used them in a while)

Eisboch


Same here. I have never had a CD that I burnt fail yet, although I do
have to clean them once in a while after being handled a lot.

What theoretically is supposed to happen to the data burnt onto CD's
over time?

"JimH" wrote in message
oups.com...



Same here. I have never had a CD that I burnt fail yet, although I do
have to clean them once in a while after being handled a lot.

What theoretically is supposed to happen to the data burnt onto CD's
over time?


I don't know. The original music CD was simply a polycarbonate disk coated
with aluminum (done in a vacuum process called "sputtering" and then
protected with an overcoat of lacquer done in a spin process.

A CD-R differs in the respect that there is an additional layer of some type
of organic dye that reacts to the laser when writing data. I suspect that
it is the stability of the dye that has been exposed to the beam that
determines storage life.

I looked around the 'net and there are all kinds of opinions on storage life
ranging from a few years to over 100 years. Heat and humidity appears to be
the determining factors, other than physical abuse or damage.

Eisboch

"Eisboch" wrote in message
news

"JimH" wrote in message
oups.com...



Same here. I have never had a CD that I burnt fail yet, although I do
have to clean them once in a while after being handled a lot.

What theoretically is supposed to happen to the data burnt onto CD's
over time?


I don't know. The original music CD was simply a polycarbonate disk
coated with aluminum (done in a vacuum process called "sputtering" and
then protected with an overcoat of lacquer done in a spin process.

A CD-R differs in the respect that there is an additional layer of some
type of organic dye that reacts to the laser when writing data. I suspect
that it is the stability of the dye that has been exposed to the beam that
determines storage life.

I looked around the 'net and there are all kinds of opinions on storage
life ranging from a few years to over 100 years. Heat and humidity
appears to be the determining factors, other than physical abuse or
damage.

Eisboch


I don't know how old this article is, but it does list results from quality
testing of CD-R's from various manufacturers:

http://www.cdmediaworld.com/hardware..._quality.shtml

Eisboch wrote:
"JimH" wrote in message
oups.com...



Same here. I have never had a CD that I burnt fail yet, although I do
have to clean them once in a while after being handled a lot.

What theoretically is supposed to happen to the data burnt onto CD's
over time?



I don't know. The original music CD was simply a polycarbonate disk coated
with aluminum (done in a vacuum process called "sputtering" and then
protected with an overcoat of lacquer done in a spin process.

A CD-R differs in the respect that there is an additional layer of some type
of organic dye that reacts to the laser when writing data. I suspect that
it is the stability of the dye that has been exposed to the beam that
determines storage life.

I looked around the 'net and there are all kinds of opinions on storage life
ranging from a few years to over 100 years. Heat and humidity appears to be
the determining factors, other than physical abuse or damage.

Eisboch




I've had a number of them deteriorate in 5-7 years, many of them were
really cheap blanks I used to backup my audio CD's and left in my car,
so in addition to being cheap they endured temperature extremes. They
weren't visually damaged but skipped more and more until they wouldn't
play. I've had other CD-Rs more than 10 years old still fine.