Prevent recovery of rewritable media

Hi you all,

I'm a bit fuzzed on this matter. I've put in considerable effort to erase my hard drive before installing a new OS to make sure that all instances of my KeePass databases were destroyed.
Naturally, I had a backup on CD-RW. At some point, I also erased the CD-RW wilth Nero 8's full erase method. I know, I could/should have microwaved it but it's in the stash of empty discs now so that train has left.

Basically, what I'm asking is, how far does optical media sanatizing and recovery go? Some privacy nightmare things pop to mind:

- Is a full erase as good as it gets or do I need to rinse and repeat?
- Is there a difference in erase quality between tools?
- If a burn a disc with burner A, and erase it with burner B, will there be data left over because burner B's positioning is slightly different compared to A's.

I'm looking forward to any insights.

Cheers,

Jeroen