WTF happend to my DVD?

After hearing of a friend’s woes I had a look at my BBC Life on Earth DVDs which I have never watched before. 2 of the 4 DVDs had a strange pattern on the data side which I have never seen before, it’s almost like a floral pattern. My friend tried to clean his without much luck but I tried toothpaste which fortunately worked. Anybody got any ideas what could have caused this?

A scan of the full CD - http://img84.imageshack.us/img84/4216/cd1lc6.jpg

A close up -http://img510.imageshack.us/img510/5056/cd2qo6.jpg

How were they stored? I notice that there is an area around the edge which seems to be free of the alien infestation.

Whatever it certainly isn’t normal. Maybe that was meant for the other side and they were loaded wrong for the process.

I doubt this is the cause but it is possible to etch the data side of a DVD. However that pattern covers the entire disk and according to the site below, you can only etch an area that hasn’t been written.

http://www.pcpro.co.uk/news/81037/nec-adds-etching-to-dvd-burners.html

It may be a “Hardcoat” product that has gone bad. It’s spun on during disc manufacture to protect the read-side from scratches. Does it flake off or can you feel the pattern?

Wow. Long-term thermal stress? I’ve had the aluminium flake off of pressed CDs when I stored them against each other or against certain types of plastic, and I have an early burned CDr where the ink ‘bled’ after being kept in my car all winter (I imagine it froze). I haven’t seen that particular mode of failure before though. It looks like the problem is with the plastic substrate, rather than the data layer.

The DVD seems to work fine now after I cleaned them with toothpaste so it doesn’t appear to be anything permanent. I thought at first that the DVDs had come loose during shipping but I don’t see how that would have caused these particular marks.

The marks definitely didn’t flake off and the surface didn’t feel obviously different.