Johannes Wilcke invented and then Alessandro Volta perfected the
electrophorus over two hundred years ago. This device was
quickly adopted by scientists throughout the world because it
filled the need for a reliable and easy-to-use source of charge
and voltage for experimental researches in electrostatics
[Dibner, 1957]. Many old natural philosophy texts contain
lithographs of the electrophorus. A hand-held electrophorus can
produce significant amounts of charge conveniently and
repeatedly. It is operated by first frictionally charging a flat
insulating plate called a "cake". In Volta's day, the cake was
made of shellac/resin mixtures or a carnauba wax film deposited
on glass. Nowadays, excellent substitutes are available.
TeflonTM, though a bit expensive, is a good choice because it is
an excellent insulator, charges readily, and is easy to clean
and maintain. The electrophorus is ideal for generating
energetic capacitive sparks required for vapor ignition
demonstrations. The basic operational steps for the