One of Japanese artist Kyosuke Hayashi's creations

Three of them are designated as National Treasures of Japan, kept in the Seikado Bunko Art Museum in Tokyo, the Fujita Art Museum in Osaka and the Ryuukouin Subtemple of the Daitokuji Temple in Kyoto. The fourth is in the Miho Museum outside of Kyoto, and the piece's existence was not widely known until fairly recently.

Up to the 1990s, it was widely believed that the techniques and quality of the Song Dynasty could not be replicated.

To learn more about the tradition and techniques of Song ceramic artisans, Hayashi traveled to Fujian to look for relics of yohen tenmoku before their glaze was changed by kiln firing.

He was lucky to find one that was exactly what he wanted.

"It was helpful in my study on replicating the yohen tenmoku ceramics," says Hayashi.

Scientists have discovered that items of jian zhan or yohen tenmoku contain a unique and incredibly difficult-to-produce crystalline formation known as epsilon-phase iron oxide.

Coincidentally, the jian zhan pieces with the highest count of this formation are also some of the most coveted for their beautiful silvery appearance.

It is believed that there was no way to control the finished product in the massive wood-burning kilns in the Song Dynasty. Because the adjustment of the fire in the kilns was left to chance when the bowls were made, their final appearance was impossible to predict.