The semi-open structure of the Bird's Nest added more difficulties to the firework show. "There were no canopies in sports venues before, which made it easier for audiences to see firework displays. This time, we had to consider the audience view inside the venue as well as interaction with the audience outside."

In order to protect the membrane of the Bird's Nest, Cai and his team chose low-temperature fireworks and conducted many experiments both in the venue and outside.

"Thousands of people contributed to our creative ideas, including the research and development of new technology, material selection, and inspection of the quality of the products," said Cai.

Unexpected art

In October 2001, Cai won applaud for a firework show in Shanghai to celebrate an Asia-Pacific Economic Cooperation (APEC) conference. He made use of 27 buildings and Huangpu River for the show, which lasted for almost 20 minutes. It was regarded as a feast for the eyes.

"Actually, I like explosions more than fireworks. I like the speed and energy of the explosion. So my designs target the vitality of the fireworks, not just how fancy the shape is," said Cai. His interest in fireworks started in 1984, when he was a student in Shanghai Theatrical Institute.

Cai is also famous for his "powder paintings." He paints by arranging fireworks in fixed lines across paper laid on the ground. The explosions leave burned areas on the paper that creates a piece of artwork.

"I have tried many ways to paint, including making use of natural wind to blow oil pigment. I always wanted to make unexpected paintings rather than just paint step by step," said Cai. "Finally I chose gunpowder. It serves as pigment for me."

In 1986, Cai went to Japan for further study. In 1991, he held a solo exhibition of his powder paintings. In 1994, he exploded a large balloon hanging in the air in the central park of Hiroshima, Japan, igniting it using a 900-meter-long fuse.

For Cai, using gunpowder explosions to create art is a natural choice. When he was young, in his hometown of Quanzhou, Fujian Province, making fireworks was an important industry.

Cai has retained his boyhood fascination with gunpowder. "It is interesting, he said, with a glint of excitement in his eyes. "It is made of dust, but after the explosion, it becomes ashes and very quiet."