The art of khruang thom, as the thais call nielloware, is believed to have come to the country during the Ayutthaya period. The precise origin is uncertain; some scholars say it came from China, while others give Persia as the source. it became a major craft in southern Thailand, particularly in Nakhon Si Thammarat, and is still practiced there

After the design-has been engraved-usually traditional, such as Thai flame or an intricate floral motif-an oxidizing solution is applied to the parts in high relief, turning them a permanent blue-black. The piece is then filed to remove all the rough edges and given a final polishing