Mao Zedong enjoying a smoke while queuing in line to be fired at the Sculpture Factory.
In the foreground are temperature “witness” cones in clay support pads which are placed in the kiln and bend upon reaching a certain temperature. In the West, ceramicists often fire a kiln using multiple sets of cones of different temperatures as guides (for instance a low temperature cone bending signals the start of reduction atmosphere, while a high temperature cone indicates the approach to target temperature). While in Jingdezhen, kilns are often fired using only a single high-temperature cone. The kiln masters (who fire kilns almost every day of their professional lives), rely instead upon sight (the color of the flames), sound, and experience.