The construction of the artificial Cloud

Icon: The Cloud

The architects Elizabeth Diller and Ricardo Scofidio from New York were commissioned by Expo.02 to construct an artificial walk-through Cloud on the Arteplage Yverdon-les-Bains. The spraying installations for the Cloud are Swiss products.

The Cloud floating above the surface of the lake in Yverdon-les-Bains is no mere illusion: the artificial mist, which is visible from afar, consists of a 60.00 x 100.00 x 20.00-metre metal construction that sprays innumerable tiny drops of lake water from 31'400 jets. Technology by the firm of BIOgenesis from Villars-sur-Glâne, which specialises in high-pressure spraying, ensures that the fleeting sculpture will be visible in all weathers, rain or shine. The architects and the different technical teams have a month in which to carry out the necessary tests.

The blur effect

The high-pressure spraying is carried out by high-grade steel jets with tiny apertures only 120 microns in diameter, through which the water is forced at a pressure of 80 bars onto fine needlepoints directly above the apertures and atomised into innumerable tiny droplets 4 to 10 microns in diameter. The droplets are so small that most of them remain suspended in the air. If sufficient jets are installed in a specific volume, they saturate the air with moisture and create the effect of mist or, in this case, the effect known as the blur.

The saturation of the air with moisture, which produces the visible mist effect, depends on a number of physical environmental conditions. These parameters include the speed and direction of the wind, the environmental temperature and the atmospheric humidity.

The temperature

The higher the temperature, the greater the amount of moisture required to produce the necessary degree of saturation.

The atmospheric humidity

When the air has a moisture level of, for example, 75 percent, the desired effect can be achieved by the addition of only 25 percent.

The wind speed

If we wish to produce a Cloud effect in a specific space, the volume of this space determines the output quantity necessary for the saturation of the air with moisture. In calm (windless) conditions the volume corresponds to the size of the space. In windy conditions, however, the determining volume is proportionate to the amount of air moved by the wind through the specific space. Thus it increases with increasing wind speed.

The wind direction

Since mist hangs in the air, it moves in the direction of the wind. Starting at the point where the water leaves the jet, a white stripe becomes visible. As soon as the air is no longer saturated with moisture, this white stripe disappears. At low temperatures with simultaneous high air moisture, the stripe is virtually always visible. When the conditions are reversed, it disappears almost immediately.

Computer-controlled spraying

Putting the Cloud into operation under consideration of all these meteorological conditions is a highly complex technical proceeding. Appropriate adjustments can be made on various levels, e.g. the placement of the spray mechanisms, the number of jets, planning of different spraying areas. The optimisation of these measures is carried out with the help of a computerised weather station that supplies the necessary information about the relevant parameters. This information is analysed by the computer and subsequently used to determine the adjustment of the spraying on the basis of conclusions reached in connection with tests carried out last year.

Diller & Scofidio, New York, United States
Elizabeth Diller (Project Director)
Ricardo Scofidio (Project Director)
Dirk Hebel (Project Manager)
Eric Bunge (Project Manager)
Reto Geiser (Design team)
David Huang (Design team)
Karin Ocker (Design team)
Andreas Quadenau (Design team)
Charles Renfro (Design team)
Lyn Rice (Design team)
Deane Simpson (Design team)

Realisation fog
BIOgenesis, Villars-sur-Glâne

Consulting fog
Thomas Mee
Fujiko Nakaya

Lighting design
Delux Theater Lighting (Rolf Derrer), Zurich

Sound design
Christian Marclay

Sound engineer
Douglas Irving Repetto

Sound installation
Nicolas Dhellin

Audio Consultant
Jens Maasen

Engineers bridges
Structures - Staubli, Kurath & Partner AG (Josef Kurath), Zurich

General contractors
Marti AG, Moosseedorf (piles)
HRS Hauser Rutishauser Suter AG (Beat Widmer), Crissier

Chantal Allemand, Ariane Allgöwer, Olivier Amrein, Roman Benninger, Nicole Boegli, Jehanne Carnal, Marie Madeleine Collet, Julia Dias, Patrick Dorsaz, Laure Favre, Simone Frischknecht, Mélita Goufas, Jérôme Grand, Julien Grobet, Nicolas Grosset, Suzanne Haziot, Christian Heiniger, David Joliquin, Anita Lovasz, Elodie Magnin Collet, Guy Metrailler, Nicolas Michel, Patricia Pache, Laure Pasquier, Stéphanie Reymond, André Riggenbach, Sven Nelson Ruffiner, Marie Schaer, Benedikt Schläppi, Eric Schmit, Ursula Schweingruber, Alexandre Seydoux, Mathieu Simonin, Christophe Spitz, Patrick Tacchini, Catherine Vifian, Fabienne Vuilleumier

Photos: © Michel Jaussi