Minerals and Metals in Ancient India v1.c26.s6.t1.7

v1.c26.s6.t1.7

The furnace structures unearthed at Zawar did not include their roof part. However, curvature of their extant brick walls (*fig. 18.2*) suggests that the furnaces probably had domed roofs with a chimney-like opening at the top, similar to those of the vertical up-draught pottery-baking kilns of Mohenjo-Daro found by Mackay (1938). The opening would have served two purposes: (1) It would have acted as an outlet for the flow of hot gases generated within the furnace, and (2) it also facilitated continuous feeding of the furnace with fuel. The use of thin cow-dung cakes could have enabled quick attainment of a high temperature with a natural induced draught of free air coming through the front opening in the condensation chamber and the smaller holes in the perforated terracotta plate separating the condensation chamber from the furnace chamber. It is significant that the banks of furnaces at Zawar face south-west, probably to receive the natural draught during April to September. The dome-shaped superstructure of the Zawar furnace was possibly dismantled after the completion of each distillation process and rebuilt again for the next batch.