In 2016, the BBC documentary Chinese New Year: The Biggest Celebration on Earth carried shots of the spectacular "canopy of flowers made from flying shards of molten metal".

Dashuhua is a traditional form of fireworks performance that takes place during certain festivals.

Using special scoops made from willow roots, the performers, who are dressed in sheepskin coats and bamboo hats, throw molten iron burning at around 1,600 C at the city walls. The molten iron then explodes into sparks that look like glittering branches of trees.

In ancient times, blacksmiths performed Dashuhua to simulate fireworks－a luxury that only the most prominent townspeople could normally afford.

According to media reports, there are only four people left in China who are able to master the ancient practice, and three of them are either middle-aged or elderly.

Due to the nature of the performance－that involves throwing superheated coal and molten iron into the air－it's easy for performers to sustain injuries. This is one of the reasons that few from the younger generations seem keen to learn about the ancient custom, says Yu Zhangliang, one of the Dashuhua performers who took part in the series.

Yu Zheng, the producer of Story of Yanxi Palace, wrote in a Sina Weibo post that the performers traveled great distances to present a sample of this endangered heritage, in the hope of bringing the ancient art to a wider audience.

"To inherit and carry forward intangible cultural heritage like Dashuhua through TV dramas is something that we'd like to do more of, and something we hope to do well," Yu Zhangliang says.

Yu Zheng, together with a group of behind-the-scenes researchers, endeavored to integrate as many authentic cultural elements into the series as they could.