This article concentrates on the regions of well salt production in Yunnan and
Sichuan in south-western China. In both provinces, salt was produced by the exploitation
of underground brine resources, some of which surfaced in the form of
springs, while others had to be tapped with the help of shaft wells and, in Sichuan
from the mid-eleventh century onwards, by deep-drilling. In Sichuan, first organic
fuel was used, such as wood, rushes or straw. From the sixteenth century onwards,
or perhaps even much earlier, Sichuan salt producers also started to use coal. Sichuan
is not only the region where deep-drilling for salt was invented, but is also where we
have the first evidence world-wide of the use of natural gas for boiling brine. In the
period between the first record of natural gas utilisation in the third century and a
more systematic use of this resource in the sixteenth century, natural gas was,
however, dangerous for the hoisting of well brine, because it caused explosions and
poisoned those lowered down into the well. The use of coal and natural gas no doubt
helped in alleviating fuel supply problems for the Sichuan salt works. In contrast to
Sichuan, Yunnan salt wells and maritime salines persisted in using organic fuel,
though for the latter the alternative of solar evaporation methods offered some way
out of the bottlenecks that beset the provision of organic fuel.