CD-R AND DVD LIFE SPAN
AND WHAT NOT TO DO!!
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CD-R AND DVD LIFE SPAN AND WHAT NOT TO DO!! |
| CD-R and CD-RW DISCS | |
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Cd-R discs are write once only discs. and
CD-RW you can write over and over again. For the purpose of archiving pictures,
CD-RW are not to be considered. They do not last and they
have a few compatibility problems with the different manufacturers ideas
of how to recorded to them. So we will only consider CD-R discs (write
once discs) from now
on. CD'R's of course are much cheaper than
there bigger brothers, DVD's CD-R's hold from 650mb to 700mb of data depending on discs. That's about 150 6mb high quality pictures. For best archival purposes set your burner up using the 650mb size when writing to the discs, if possible. The recording system used at 650mb is closer to the true CD standard giving maximum compatibility. also always burn Cd-R's below the manufacturers stated top speed.
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Construction of CD-R |
Construction of normal (music and software CD) |
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Study the different construction methods
used. The laser reads through the bottom surface of the disc (the side
we always worry about scratching). You will see that ordinary CD's have a plastic layer
added between the data layer and this surface. But
look at the the CD-R (LABEL SIDE). We have 3 very thin layers laid onto
the just one piece of plastic. The data/reflective layer is just below
the label. Your data is just below that label. Press to hard with that sharpie!!!
Use some labels and they can also peel off taking
the data layer with it. Over time some solvents from pens
and labels will work there way down and oxidize the reflective layer as
well!! Oxidized silver reflective layers is the most common cause of CD failures. Some manufactures make a point of silk screening tough labels to help protect these data layers below. Promaster gold disc being one type. There are special pens ("xylene-free" marker pens) for writing on the discs. As to the many different types of labels, the jury's still out. and goes with saying if they peel off they are going to take some of your label and data layer with them!! Just treat the label side of your CD-r's with respect from now on. and write on them using the write pens. Before moving on to the subject of how long they CD-R will last, any discs with GOLD reflective layers, can not suffer from oxidization. These are a good pointer towards a good archival discs. But gold is expensive. Some manufacturers call their discs gold discs, but this refers to the die only not the reflective layer. DVD DISCS Most Recordable DVD have a plastic protective layer added below the label, so do not suffer from some of the problems mentioned above. Except to point out some solvents from wrong pens and labels will work there way through this plastic layer over time and oxidize the reflective layer still. There are two main types of discs out there DVD+R / DVD+RW and DVD-R/DVD-RW( sometimes called dvd ram). Again I will stick my head on the block and state that the rewritable flavors, DVD-RW and DVD+RW discs are not to be recommended for archival purposes, which is the purpose of this article. DVD-RW is totally incompatible with nearly all standard DVD players. If you are making DVD movies or still pictures shows to view on a standard DVD player on your TV, DVD+R is the nearest to the standard for DVD. But you will find most modern players will play both the recordable once DVD-R and DVD+r discs well.
HOW LONG WILL MY DISCS LAST? Taking aside the label side issues covered already. All Recordable CD's and DVD's use a dye to record the data onto. the change in color caused by the laser is treated as 010101's, which is the only thing computers really understand anyway. (I got to count past one in 1st grade ;-). The dies used by the different manufacturers all have different properties. They will all be affected by exposure to UV light, so don't store your archive discs on the car seat! Keep them in a archival type album or the plastic cases. There is even talk of some of the perspex cases giving off harmful gases which effect the discs (All those millions developing CD's and they still can't make a plastic case that does not break when you look at it). So many things influence how long the discs will last, construction, materials used, conditions of storage etc. Just buy good brand discs and store them in a safe dry dark place. Now to the dies used to record your data. The problem here is that manufacturers don't normally tell you what dies are used, and we can't tell sometimes because the reflective layer alters the disc color as well.
TIPS: Always verify your disc is readable before you put it away.
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For more in depth info visit the OFFICIAL STORAGE TECHNOLOGY ASSOCIATION
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