Slow Visco A visco fuse is a higher quality fuse used for consumer fireworks. It is most commonly colored green or red, and is found as a twisted, coated strand. It is also used to create safety delays in the hand firing of fireworks. Visco is a 2-5mm diameter cord with a black powder core. There are three external layers to visco fuse. First, a layer of string is wound around the core, then a second, less tight layer of string is wound in the opposite direction to prevent unraveling. The last layer is a low-nitrate nitrocellulose lacquer that keeps the fuse from falling apart. The last layer helps to make the visco fuse water resistant and to prevent moisture from degrading the black powder core. Unlike dynamite safety fuse, visco fuse burns with a visible external flame. After ignition, most visco fuses can burn underwater. Burn speed: ~1cm/s Classification: 1.4g 2mm AND 3mm Visco Burning Note how the larger in diameter the visco is the more fiercely it burns.