Cut two strips of aluminum foil 3 inches wide and 36 inches long.
Cut two strips of wax paper 3 1/2 inches wide and 37 inches long.
Lay one strip of wax paper on a flat surface. Layer one strip of aluminum foil centered on the strip of wax paper. Tape an unbent paper clip to the strip of aluminum foil, overlapping the top right edge of the strip of aluminum foil by 1 inch.
Layer a strip of wax paper centered over the strip of aluminum foil. Layer the second strip of aluminum foil over the second layer of wax paper. Tape an unbent paper clip to the strip of aluminum foil, overlapping the bottom left edge of the strip of aluminum foil by 1 inch. The paper clips should be at opposite ends and pointing in opposite directions.
Roll the layered strips carefully and tightly from one end to the other. Wrap tape around the roll to prevent the paper/foil from unraveling. Light a candle and drip the melted wax on both ends to seal the capacitor ends. The paper foil capacitor is now ready for charging; use the two paper clips as leads to connect to a battery.