Johnson Estate Sculpture

Environments 21 March 2011 | 10.00am

Over the last couple of years I have been one of the team working on the Johnson Estate Sculpture, designed by Chris Booth for Sydney’s Royal Botanic Gardens. Sculptures can be fascinating projects to work on, they can push the realms of what is technically feasible and they are projects where great bonds can be built with the artist. As a result they are also excellent projects for sparking innovation.

Johnson Estate Sculpture 1

The Johnson Estate Sculpture is the outcome of a bequest in the will of the late Ronald Johnson. The will directed that a substantial sum of money should be used to provide a work of sculpture to be placed on the Sydney Harbour foreshore. Following an international competition, the Trustees of the Estate selected Chris Booth, an internationally renowned sculptor from New Zealand, to develop the sculpture. The site chosen for the sculpture is close to Government House in the Royal Botanic Gardens.

We started the project working with Chris Booth’s 1:50 scale maquette in clay. This was the ‘contract document’ that defined the intent of the sculpture. To move the maquette to a digital model a 3D laser scan was made, with the resulting point cloud becoming the geometrical background for further model geometry to be created, which was done in Rhino3D.

Johnson Estate Sculpture 2

The work comprises 2 separate components, the Quartz form and the Sandstone wave form and we used various 3D products to virtually construct and review the entire sculpture through interactive review meetings with all parties involved in the project.

The hollow quartz form is a skin made up of about 16,000 quartz pebbles threaded and woven together with stainless steel cable and wire that is supported by an invisible internal stainless steel structure. A very special Sydney Aboriginal shield design will be the feature of this weaving. It is woven into the quartz form using ochre coloured Nepean River pebbles. The original of this shield is in the Australian Museum and approval for its replication has been given by the Gadigal Aboriginal Community whose ancestors lived in this Sydney region.

Johnson Estate Sculpture 3

The sandstone wave form appears as three undulating strata emerging from the ground. Their undulation and separation is reminiscent of strata that have been subjected to land movement due to tectonic forces. This form was constructed out of about 260 Hawkesbury sandstone blocks quarried from Gosford Quarries. These large blocks – up to 3 metres in length and half a metre thick are bolted together with stainless steel bolts drilled through them in such a way as to be invisible in the finished sculpture. Each block was cut to shape and drilled for the bolts from a detailed drawing generated from the 3D model.

Johnson Estate Sculpture 4

Clash analysis software was used to prove bolting arrangements of the stone blocks was achievable. High dynamic range laser site surveys were used to measure installation tolerances against the digital model and 3D PDF’s were created and used by stone mason’s site team to understand the irregular shapes of the stone blocks and assisted in understanding of the installation sequences and propping locations.

The sculpture was opened on 9th March and has been named Wurrungwuri (‘This side of the Water’)

Jeff Casson, John Hewitt, Peter Jameson, Alex Edwards, Stuart Bull, Kai Nelson, Rick Benjamin, Chris Mawson & Bruce Moir

Traditional Stone contractors
James Ginter

Gosford Quarries (supplier of sandstone and fabricators)
Garry Boyce, Phil Brown & Greg Cook