Without the capacitor, a static generator such as the one made with PVC pipe would have to be operated in a very dark room in order to see any sparks produced. The capacitor stores up enough of a charge to make a very visible spark in broad daylight and, can also be heard. The picture of the film can leyden jar is self explanatory. The inside foil can be taped to the wall or secured any way you want, so long as it makes good contact with the wall. One person wrote back and reported that the film can exploded as a result of using rubber cement to glue the inside foil to the wall.
Rubber cement is highly flammable and explosive and was set off by sparking inside.
28 Mar. 1996.