How the life of CD-ROM is long? Initial estimates put
the life expectancy of an optical disk at 50 to 100 years. Recent speculation
has reduced this to from 3 to 5 years. Many users worry about losing valuable
data after paying high subscription costs over a short period of time. The
problem becomes particularly acute for one-time purchases and for full-text
databases such as encyclopedias and multi-media materials for which equivalent
counterparts do not exist.
The National Science Academy has found a solution to
this problem. Acccording to one of their recent studies, they have determined
that the deterioration and oxidation process can be delayed, therefore, prolonging
the life of a CD-ROM. They recommend that when the discs are not in use, they
be stored in the freezer at 17 degrees Fahrenheit. This action should prolong
the life expectancy of CD ROM by 75 years or more. They suggest using zip lock
bags to seal in the freshness of the data and to prevent freezer burn.
In addition, they recommend using Arm and Hammer or
another brand of bicarbonate of soda to absorb harmful gases and reduce
oxidation. This process resembles freeze drying which keeps the disc dry, kills
bacteria, and preserves the medium. The bicarbonate of soda removes harmful
odors and other bacteria from the air which could accelerate the oxidation and
deterioration of the disc.
When preparing the disc for use, they recommend
allowing it to warm to room temperature prior to inserting it in the CD ROM
drive. While one could use the microwave to do this, they do not recommend it,
except on July 4th. One could also use a toaster set to the light cycle to warm
the disc and remove any condensation. A one quart sauce pan or a small frying
pan would achieve the same results. The sauce pan has an advantage in that it's
just about the right size to hold a CD-ROM; and it heats the entire side
evenly.
To avoid having the discs stick to the pan, however,
the National Science Academy's report recommends using a little margarine or
vegetable oil to coat the pan bottom. They suggest using safflower or a
low-cholestorol oil. An even coating will also facilitate even heating. Oil
residue on the discs provides a protective coating during use that blocks the
air from attacking the disc, thereby preventing oxidation. It also lubricates
the disc surface, permitting it to spin faster. As the disc moves faster, more
data pass under the optical pick-up unit, thus speeding up information
retrieval.
In using this approach, however, one should not insert
more than one disc at a time because the second and subsequent discs will not
heat uniformly. Even heating is important to avoid read-back distortion caused
by excentricity resulting from heat expansion. Users should beware using too
much oil (lubricant), however, as this may cause the data to "slide"
to the outer edge during the spin cycle, thus causing them to become
unreadable. In addition, the coagulation of too much data on the outer edge
("data bunching") could produce unbalancing of the disc that could
impair operation -- just as an uneven load of laundry in the washing machine
produces noise during the spin cycle. This phenomenon also provides an argument
against using vertically-mounted drives. Overly-lubricated data could slide off
the disc and fall to the bottom of the drive unit, resulting in substantial
data loss and a messy clean-up job.
If this latter problem occurs with any degree of
frequency, drive manufacturers will probably respond by installing a
self-cleaning mechanism in the next generation of drives. This mechanism could
work in a manner similar to self-cleaning ovens, or it may involve coating the
inside of the drive chassis with teflon or a similar non-stick surface to make
cleaning easier. Many existing drive models have a multiple-door mechanism to
seal the optical unit from the rest of the chassis to prevent dust and foreign
matter from entering the drive. However with contamination coming from internal
operation, a self cleaning mechanism would be most appropriate.
The National Science Academy has determined that
following these procedures could eliminate the problems of oxidation and
deterioration, thereby prolonging the life expectancy of a CD-ROM almost
indefinitely.