All materials, both insulating and conductive, are static electricity sources. These materials are associated with positive (proton) or negative (electron) tasks and are of equal value.
Electrons by convention have the charge (-), and the protons have the opposite charge (+). In general, particles with the same sign load are rejected, and those of opposite signs attract.
The location and measurement of the electrostatic field is thus very important in many applications.
SIMCO FMX-003 is a very good device for locating and measuring the electrostatic field.