The finished dye is made using water from boiled cowhide, and egg whites. The cloth is wrung, scrubbed and pounded, before it is turned into traditional Dong garments — dark indigo outfits with a colorful flower trim for the women, plain for the men.

Hu Xiaomei, a researcher and curator at the Ethnic Costume Museum at the Beijing Institute of Fashion Technology, says that indigo dye has been used for centuries to make textiles. It can be found in many cultures, and its use in making Dong cloth is well-preserved and recognized.

Yang Shenghua says the process of making cloth is complicated and involves many steps, each of which is time-consuming. "It is like a construction project," she adds.

She says that her mother was strict about the making process. "She preferred to leave the cloth to dye for longer than usual to achieve a really dark blue. Then, you had to starch, pound, dye, dry and pound again. …All I can remember was repeating those steps again and again.

"Once you have made a mistake, you'll make more. This is really frustrating, as you need to start all over, and be focused and cautious to avoid making the mistake again," Yang Shenghua says.

Hu says the cloth is pounded to flatten the outer layer of cotton threads. This leaves no space between the threads, and tightens its structure.