Question Data CDs shows as blank when actually is not

[Mk56TClaire]

I want to copy my old data from CDs and DVDs to my PC. I haven't used optical drive for a long time (my old laptop broke since 2015 [the optical drive was dead years before], my father's laptop optical drive is dead, my PC doesn't have one), so I bought an external optical drive (this one).

While it's able to read data DVDs and some CDs, some other CDs shows as blank (702MB free of 702MB). I'm pretty sure they aren't blank.

What caused that? Is the optical drive is too modern or my CDs are too old?
But the CDs that successfully read (and the DVDs) are the same age with the "blank" CDs. They are from 8-10 years ago.

 

[jojesa]

There are many variables that could cause a CD to appear blank even though there was recorded data to it at one point.

-If the disc were not finalized, only the program use to write the CDs can read them.
-There could be physical damage to disc surfaces or edges. A small damage where the data directory is located will show a blank disc.
-Chemical reactions with contaminants.
-Light damage.
-Corrosion (oxidation) of reflective layer
-Cheap CDs might just break with age. Adhesives between layers could come apart (de-bonding).