You have to be careful about what materials you use to construct your Leyden jar. The material must serve as an insulator between the inner charge (+) and the outer charge (-). Choose a glass jar or a plastic bottle with a lid., You will need a conductive material inside the jar in order to charge it. Traditionally, water was used inside the jar. To build a more modern Leyden jar, you should line the inside of the jar with metal foil (tin foil, aluminum foil, etc). Your conductive material will become positively charged when you charge the Leyden jar., You will need an electrode protruding from the jar to charge the inside of the jar. You can do this by hammering a nail through the lid of the jar. Make sure that the nail goes far enough into the jar to contact the conducting surface inside the jar (water, foil, etc.).You can also connect a chain or other conductive material to the nail and allow it to hang down and touch the inner conducting surface.
 Wrap only the bottom and part of the sides of the jar. Stop short of the mouth of the jar. The foil on the outside of the jar should not contact the foil on the inside of the jar. The outer foil will have a negative charge with respect to the inner foil.
Choose a jar.
Place foil inside the jar.
Insert an electrode into the lid.
Wrap foil around the outside of the jar.
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