layered as to produce different effects at different stages in the burning. For instance, one layer may burn to produce orange sparks, followed by a layer that produces white sparks and green star fragments.single tube fountains consist of a cardboard tube (which may be inside of a cone) that stands vertically on a plastic base.  The tube is charged with a composition designed to make lots of sparks, flame, and gas.  At the end of the tube there is a clay plug with a hole drilled into it, forming what is known as a "choke".  Without a choke, the fountain would only give off a weak spray of sparks.  With a choke, however, a lot of pressure builds up inside of the tube, which forces the gas and sparks out of the fountain with a much greater velocity.  Very small fountain tubes (i.e., 1/4 in diameter) don't require chokes.