Place a penny on a piece of aluminum foil and trace around the penny with a pencil. Repeat the process 10 times until you have 10 penny-sized circles on the piece of foil. Cut the 10 penny-sized circles out of the sheet of aluminum foil with scissors.
Lay down a paper towel and lay a penny at one corner of the towel. Draw a square around the penny, so that the penny just fits inside the square. Cut the square from the paper towel.
Use the first square from the paper towel and use it as a guide to draw 19 more squares of the same size on the paper towel. Cut out the other 19 squares of paper towel, so that you have 20 paper towel squares.
Place one penny down on a flat surface. Cover the penny with a square of paper towel, place a circle of aluminum foil on top of the paper towel and cover with another square of paper towel. Repeat the penny, paper towel, aluminum foil circle, paper towel pattern until all of the items are stacked, with a penny at one end and a circle of aluminum foil at the other.
Tape one of the wires to the penny end of the stack with electrical tape and the other wire to the foil end of the stack. Then, tape the entire stack from one end to the other to keep all of the parts together in the proper order.
Create a solution of salt water by stirring a teaspoon or so of salt into a glass of warm water until dissolved. Drop the entire penny, paper, foil stack in the salt water solution and allow it to soak for a few minutes.
Retrieve the stack from the salt water solution. Connect the wires that are connected to the stack to the wires of a voltmeter to view the voltage of the stack.