Visco is a type of rugged water proof fuse that is used to light fireworks. Most visco fuse is green in color, but is available in almost any color. Because visco fuse is know to spit fire when it is lit, you should never light visco directly with a match or anything that would put your fingers in close proximity to the fuse. Instead, visco should be lit with a propane torch, a road flare, or a long punk (see definition for punk above).