Ten years ago, Cyril Bateman did a great series of technical articles on capacitors in 'Electronics World Magazine'.
You would need to do a search, as the papers do not seem to have a permanent URL.
Cyril Bateman Articles
Electronics World Magazine
Capacitor Distortion: Part 1 Cyril Bateman July 2002 p12 S
Capacitor Distortion: Part 2 Cyril Bateman Sept 2002 p16 S
Capacitor Distortion: Part 3 Cyril Bateman Oct 2002 p12 S
Capacitor Distortion: Part 4 Cyril Bateman Nov 2002 p40 S
Capacitor Distortion: Part 5 Cyril Bateman Dec 2002 p44 S
Capacitor Distortion: Part 6 Cyril Bateman Jan 2003 p44 S
Capacitor Sounds II: Part 1
Real-Time Hardware Cyril Bateman July 2003 p36 S
Capacitor Sounds II: Part 2
Distortion v Time v Bias Cyril Bateman Aug 2003 p46 S
Capacitor Sounds II: Part 3
Distortion Meter Cyril Bateman Sept 2003 p46 S
Capacitor and Amplifier Distortions Cyril Bateman Nov 2003 p44 S