Why cant you use a conductor in a capacitor instead of a dielectric medium?
A capacitor needs a capacity to store energy, which means that a dielectric material having the property of polarizability, a conductive material will turn it into a resistor.
There are only two types of ideal electrical materials.
insulators and conductors.
insulators : all insulators are dielectrics which are also capacitors. they store loads.
conductors: all conductors have negligible capacity, because the mobility of electrons in the conductors (usually metals) is very high, so that the electrons move freely and bounce depending on the temperature. exceed absolute zero and create waves of electron-beam brigade effects moving in a conductor. the electrons do not actually move at the speed of light in a perfect current pulse in a conductor, only the chain daisy or wave of hands in the audience moves at the speed of light in that dielectric. the dielectric also controls the speed of light, so it moves more slowly in a coaxial cable with high dielectric constant (type 2/3 c)
if you soil an insulator with a conductive spray, not only does the resistance drop , but also capacitance, because instead of a single large capitalization, you have a series of tiny capitals in series that increase their value per unit of width over space and are unloaded faster.
remember that in most applications, the best capacitors have not only the lowest conduction, the lowest parallel leak or the highest resistance for the nominal voltage, but also the best conductive interface with sprayed surface to increase contact area and reduce series resistance.
Does this imply a kind of universal rc constant for materials of different surfaces in the same volume, which means a different number of layers in parallel or series giving different values if c?
Take any family of dielectrics and get the c, esr, rleak and ts calculation, tp for serial and parallel leaks and see why you are discovering for esr * c and see which ones are the best or are they almost all identical? for a given voltage and dielectric type. low electrode vs high density electrolytic vs high density k and density std ceramics vs low esr, plastic caps with low leakage but very low density k.