These thick-walled spouted vessels were made of clay. Analysis of the interiors shows that they were used to melt bronze, copper, and tin for casting in molds. A notable feature of crucibles in the Ban Chiang area is lagging, the thin quartz-rich clay layer deliberately added to the interior of the crucible. The lagging layer would tend to reflect heat into the metal and also retard crucible disintegration. The use of a lagging layer indicates that the Ban Chiang metalworkers possessed a sophisticated understanding of refractory principles. Some crucible fragments have several layers of lagging, indicating that they were used repeatedly.
Read more about the process in the following articles:
- Chronological Variation in Crucible Technology at Ban Chiang by William W. Vernon
- Preliminary Cultural Implications from Initial Studies of the Ceramic Technology at Ban Chiang by Joyce C. White, William Vernon, Stuart Fleming, William Glanzman, Ron Hancock, and Andrew Pelcin