Innovation in the Manufacture of Salt in Eastern Australia: The 'Thorn Graduation' Process

Salt production in nineteenth-century Australia was often based on the evaporation of sea-water by boiling. This required large quantities of fuel because of the low salt-content of sea-water, and there were obvious advantages in pre-concentrating the brine before boiling. Although solar evaporation was a well-established way of doing this, a handful of Australian manufacturers attempted to use the 'thorn graduation' process, in which water was evaporated from the brine by trickling it through high walls of brushwood. In this paper Brian Rogers, of the Institute of Advanced Education, University of Wollongong, shows that this was a technology with a long history at salt springs in continental Europe but that its use in eastern Australia for concentrating sea-water appears to have been a significant innovation. The author suggests that the lack of success of this process in Australia resulted as much from economic factors as from any technological shortcomings.