There are 3 common ways to generate static electricity, triboelectric generation, field induction, and direct charging. Triboelectric generation (tribocharging) is the most prevalent method for charge generation that needs to be well understood to control properly. The Triboseries is illustrated in the graph below and will help give you a better understanding this phenomena. Tribocharging can occur on both insulators and conductors.

A listing of materials, with respect to the polarity and magnitude of charge generated during contact and separation is called the Triboelectric Series. The series is arranged so that those materials at the top of the list lose electrons and charge positively when rubbed with materials below them relative to the Series. Conversely, the materials at the bottom of the list gain electrons and charges negatively. The farther away the materials are from each other within the list, the greater the magnitude of the charge is generation by them under tribocharging conditions.

The series should be considered a guide to both polarity and relative charge magnitude for various materials. Frequently, one finds some slight inconsistencies in magnitude between two materials from what the Series indicates. Sometimes complete reversals of material positions have been observed.

The most common example of tribocharging is a person walking across a floor. Depending on the materials involved, i.e., soles of the shoes (leather, rubber, wood, etc.) and the surface of the floor (nylon or wool carpet, vinyl tiles, cement, wood, polyurethane, etc.) the resulting charge on the shoes and balancing charge on the body will be dependent on the charge accumulation from area, frequency and contact force of the contact and separation (triboelectric generation) process. Voltages as high as 5kV at 40% RH were reported on a person after walking across vinyl flooring which can certainly be felt when discharging to a metal object (doorknob).