Harappan stoneware bangles 40 years later: possible invention of a pressure-release valve in the early Bronze age

This paper proposes a re-consideration of the complicated firing apparatus for stoneware bangles used by Harappan potters at Mohenjo-Daro, in the second half of the 3rd millennium BC. In fact, an important technical detail of my previous reconstructions was wrong, and the error has probably contributed concealing a crucial implication: the possible original discovery in the Bronze age of the principle of pressure release and control in pyro-technological processes. That modern metallic pressure valves may have had an ancestor in Bronze age pottery may be surprising, but, once more, it stresses the important roles of similar "virtuosistic" applications in Indus Valley ceramics. The overly emphasized pyrotechnology of Harappan craftpersons may have contributed to building up a solid, if latent know-how, which somehow survived urban devolution, to be discontinuously exploited in much later socio-technical contexts.