For example, most people think of wood as an insulator. It is, but only up to a point. Another example would be to examine a new roll of electrical tape. Rubbing a balloon on your head can generate thousands of volts. But wait- there's more.
High voltages can leak off of conductors.
It depends on the radius of any given edge of the conductor, and how much voltage is on it. That's why conductors on electrostatic equipment are usually very smooth and round. You don't see wiring on them because wire is generally too small of diameter to hold a great deal of voltage. The less leakage there is, the more voltage can build up. In any case, there is more to read on the Internet and in books about this, so if you need to, go for it.