Medusae Nilfisk, Roskilde Festival (2007)

The Medusae spheres, made from recycled parachute material, are lit from within and cycle through the colour spectrum. They are suspended by antique Nilfisk vacuum cleaners. A propane-driven flamethrower ignites when people make human contact between two poles on the ground. The Medusae Nilfisk was originally commissioned by Roskilde Music Festival (the largest music festival in Northern Europe) in 2007.

Three giant spheres are pulsating, lit from within by an everchanging interplay of the full color spectrum. The wind moves the enormous surfaces of fabric and recycled parachutes suspended by antique Nilfisk vacuum cleaners. At night the floating color cycles reflect in the surrounding buildings, trees and water.

On the ground, two metal poles with green diodes attract attention, along with a lit cryptogram. To reach between the poles and activate the Medusae Nilfisk pyrotechnics, you must join hands with at least two more people and form a chain. When the low voltage current connects through the bodies, the three spheres go white, for instance, and…waughhh, a huge burst of flames erupts into the sky, casting an intense fire glow on the whole area. Now the visitors might start to play with creative solutions for igniting the explosions, long chains of people holding hands, couples kissing or acrobatic stretches. Any physical contact between the poles will set off the flamethrower cycle.

The Medusae installation consists of three large constructs, each 8 meters high and made primarily from recycled materials. The main structures are steel pipes salvaged from a scrap yard. The spheres are made from surplus parachutes treated with a sealing compound and anti-flammables and four old vacuum cleaner engines set in the baseplate of each sphere. A propane-driven flamethrower system is mounted on the top pole, made from old water pipes, magnetic piston valves and custom-made nozzles. The ignition system is made from parts of the high-voltage system found in old central-heating boilers.

Inside the spheres is a system of lamps in the primary RGB colors and white, enabling the individual Medusae to attain almost any color; and the three Medusae to transform in any color combination.

The public interacts with the Medusae Nilfisk light cycles and flamethrowers through a collaborative effort, creating contact between the two poles. When people join hands or establish another physical connection, it is registered by the control systems and ignites the gas explosions. A built-in timer sets a limit to the number of explosions in succession.

The lamps consisted of two parachutes sewn together and dipped in glue. The parachutes were filled with air by four Nilfisk vacuum cleaners running in reverse. The lights consisted of four (red, green, blue and white) 2,000 watt halogen light bulbs. The lights were controlled via DMX by a Wiring board (Wiring, n.d.). The Wiring board shifted through Hue in HSV colour space. The signal to noise ratio between the two poles was measured so that when the two poles were connected, the wiring switched to explosion mode, where it ran through a colour cycle before setting off relays connected to solenoids in the three gas cannons. It then released the gas into the atmosphere while turning on a spark gap to create an explosion.

Credits: Bo Boye, Harald Viuff, Mads Hobye, Nicolas Padfield, Nikolaj Møbius, Schack Lindemann, Thomas Jørgensen and Vibeke Hansen.