The wet Leyden jar method relies on storing electric charges between a metal foil and an electrolyte solution. This is accomplished by filling a jar 2/3 full with water and adding some salt. A plastic lid with a hole drilled through the center tops the jar. The outside of the jar is wrapped with aluminum foil directly opposite the electrolyte. A short length of wire is attached to the foil to act as one lead. A longer length of wire is fed through the hole in the lid of the jar until one end is immersed in the electrolyte. The other end extends outside the lid and serves as a second lead. The jar serves as the insulating dielectric between the foil and the electrolyte solution. The two leads are used to charge and discharge the wet Leyden jar capacitor.
The dry Leyden jar capacitor uses two foils separated by an insulating dielectric rather than a foil and an electrolyte solution as found in the wet Leyden jar capacitor. A simple dry Leyden jar can be made out of a plastic film canister with foil wrapped inside and outside of it. A copper wire is then taped to the outside foil for one lead, and a second copper wire is taped to the inside foil for the other lead. A small hole is punctured through the plastic lid for threading the inner foil wire lead.
The paper foil method is a way to make a compact condenser. The paper foil method involves layering alternating strips of paper and metal foil, followed by rolling the layers as one into a tight roll. The paper layers serve as the insulting dielectric between the foil plates. Prior to rolling the strips, a copper wire is attached to the bottommost metal foil and to the topmost metal foil. The number of layers of foil directly affects the power of a capacitor. The more layers of foil used, the more electricity the capacitor can store.
The air variable method is a simple capacitor type where flat plates of metal that store charge are separated by air that serves as the insulating dielectric. The plates can be as simple as two in a frame with one plate sliding in and out over a stationary plate. Sliding the one plate varies the amount of charged plate surface opposed to the other plate. When a sliding plate partially covers a stationary plate, there is partial capacitance. When the sliding plate totally covers the stationary plate, there is full capacitance. Therefore, the capacitor is variable in the amount of charge it can hold.