Anthony McCall. ‘Column’ studio model (2011).
An Interview with John McNulty.‘Column’ is a spinning, ascending, hollow, flexible cylinder of air and water vapour, approximately twenty metres in diameter that works via coherent convection. It will be generated by a structure floating on water. The structure is made from standard construction materials, specifically a steel framework, standard scaffold poles, sheet aluminium, ties and fastenings, buoyancy floats and mooring chains. The structure will hold pipes that will provide rotation, aeration and humidification and will be driven from dry-land electric pumps, generators and switches. The larger part of the structure will sit just below the surface of the water.
Combining rotation and ascending warm moist air with extra heat starts the ‘thermo-siphon’ effect. After being switched on, ‘Column’s’ tube of air and water vapour will ascend up to and beyond cloud base. It will keep climbing for about thirty minutes until it connects with the upper Troposphere, after which it will become a relatively self-sustaining ‘syphon’. Powered by the difference in temperature between the natural ‘waste’ warm, wet air at ground level and the low pressure sub-zero environment at the column’s top, this temporary, ephemeral and dynamic structure can be switched off at will. The siphon operation is completely silent.
The column’s spin helps it rise through the comparatively higher-pressure surrounding atmosphere, even if it is buffeted by winds. Winds often veer in different directions at varying heights and the column will bend sinuously in response while retaining integrity during its climb to the low-pressure sky.
Nature produces such columns randomly, thousands of times a day, all over the planet. This is the same natural mechanism used by desert dust devils. A dust devil’s visibility stems from the spinning air entraining sand or dust, whilst waterspouts, like our column, are simply hollow air tubes with visibly condensing mist/cloud at their boundary layer.
Normally, when convection confronts upper layers in the atmosphere, its energy dissipates and loses coherence to friction and turbulence. But the rotating column imparts an outward force, which is then balanced by the surrounding atmospheric pressure pushing inwards – this dynamic system is known as cyclostrophic balance. Following nature’s lead, ‘Column’ works by deliberately focused convection and maintains its integrity by cyclostrophic action, so we have fully anchored control at all times.
The column’s visibility depends upon its own warmth and humidity versus local weather conditions. As the column of warm air ascends, its boundary layer meets the surrounding, colder air. This causes condensation at the thin outer layer – creating our visible, hollow ‘column of cloud’. During the day, the column of cloud will be illuminated by sunlight and its appearance will vary as much as the weather itself.
John McNulty