Some CD tweaks are listed at the EVS site, including a pic of a totally treated CD (it's not obvious that the edges have been inked, but the text indicates they have).
http://www.tweakaudio.com/Cd%20tweaks.htmlTry this if you can--get two identical CD's and treat one but not the other.
I have a flawed Cassandra Wilson CD that won't play one track, so I bought another to replace it: inked the flawed CD (figuring it wouldn't be a tragedy if I ruined it), played the unflawed tracks and noticed a benefit to the inked CD.