We finally have an answer: The beginning and the end of the sliding motion that produces static electricity experience different forces – resulting in a charge differential between the front and the back that results in the crackle of static electricity.
That would explain why rapid spinning films over a surface build up incredibly powerful static fields. It’s been observed that the contact surface area doesn’t seem to matter, and it’s easier to build up with greater velocity. It’s all about where the energy is going, and it’s into those imperfections. Cool