Methods for calculating brine evaporation rates during salt production

Salt is recognized by archaeologists as an important commodity due to the biological need for sodium and other cultural uses. Numerous studies have described the various techniques used in converting brine to crystallized salt, but few, if any, have attempted to quantify the physical processes of evaporation in pre-industrial societies. Apart from the few areas where salt mining is possible, nearly all forms of salt production require evaporation of water to concentrate brine and ultimately produce salt crystals. This study quantifies three of the most common evaporation techniques and provides insight into the production rates of salt and fuel requirements. Methods of calculation are provided for determining evaporation through (1) direct solar heating of brine, (2) applied external heat to a vessel, and (3) an immersed heated object (e.g., stone). These results provide physical constraints on the evaporation process and provide investigators with techniques for estimating efficiency and total production of prehistoric and historic saltworks. (C) 2007 Elsevier Ltd. All rights reserved.