He is very proud of a 34-centimeter-tall bottle with a small mouth and bulging belly, the shape inspired by short columns on the beams of traditional architecture in suburban Suzhou.

Yu and his team spent three years producing this bottle, which weighs only 478 grams and is made from a raw material of 39 kilograms. The belly is 11 cm in diameter and the mouth is just 2 cm. They had to apply mini tools to hollow out the interior a little at a time, "like cleaning ears", he says.

While hollowing out this piece, the artisans could barely see the inside and had to rely largely on feeling with their hands. Yu explains that it's a risky process to make eggshell jade pieces, as a slight tremble may puncture the whole piece.

The surface of the bottle is adorned with symmetrical relief patterns featuring intertwined winter jasmine and lotus, both bearing auspicious meanings in traditional Chinese culture.

Variations in color result from the change in thickness of the carvings on the green nephrite — with the thinner part being lighter and the thicker part with relief patterns appearing much darker.

The eggshell jade master is just one practitioner striving to protect the millennia-long prosperity of antique craftsmanship in Suzhou.

Late Ming Dynasty (1368-1644) scientist Song Yingxing wrote in his masterpiece Tiangong Kaiwu (The Exploitation of the Works of Nature) that although fine jade materials were always brought to the capital, Suzhou possessed the most exquisite craftsmanship.

According to Ma Jianting, president of the Suzhou Arts and Crafts Industry Association, regional characteristics of jade carving, as well as the exchange and integration of craftsmanship, have lasted throughout the modern era.

For example, artisans in the north have inherited the traditional style of grand, complex royal pieces. Jade artisans in Yangzhou, historically taking advantage of the convenient transportation of raw materials by the Grand Canal, are good at carving large pieces such as mountains.

Suzhou-based carvers, on the other hand, are focused on smaller pieces with delicate, reserved designs that resonate with the city's gentle atmosphere, says Shan Cunde, the association's deputy secretary-general.