[Video/ntfabu.com]

A Nantong blue calico exhibition kicked off at the Jiading Museum in Shanghai on July 22 and will run until Sept 12.

On display are more than 180 works from the collection of the Nantong Blue Calico Museum, including some dating back to the Ming (1368-1644) and Qing (1644-1911) dynasties.

According to historical materials, blue calico originated during the Southern Song Dynasty (1127-1276) in Anting town, Jiading district, Shanghai, which was then under the jurisdiction of Suzhou.

It soon spread to neighboring Nantong, a major production area for cotton and Strobilanthes cusia, from which natural indigo is extracted, and became widely consumed. 

In 2006, the Nantong blue calico production technique was listed as a national intangible cultural heritage item.

The cloth has a complicated production process and is made almost completely by hand.

The first step involves carving out motifs on a thick paper template by hand. These patterns are then transferred onto white cotton cloth by brushing a dye-resistant paste made with lime and grounded soy bean over the template. It takes about three days for this paste to dry, after which the cloth undergoes the dyeing process.

Natural indigo dye is extracted from Strobilanthes cusia by grinding and fermenting its leaves. The dye is then poured into a large caldron where the cloth is immersed a number of times until it turns an indigo color. 

Next, workers extend the cloth and scratch off the dye-resistant paste, leaving behind white motifs underneath. The last step in the process is washing the cloth to remove any remaining particles and hanging it out to dry on poles.

During the exhibition, a blue calico workshop will also be held weekly, allowing visitors to try their hands at the ancient art form.