To produce woad balls, the leaves are first crushed, and ground in a grinding bowl or a mortar with a stone or wooden pestle. Then the crushed leaves are kneaded with hands into balls, each of which weighs around 500g. After the balls have completely absorbed the excess of the sap left in the bowel, they are left to rest for 14 to 20 days in the sun to be dry through. Each dry woad ball weighs around 60g.
To build woad vats, 700g of woad balls are again broken into small pieces, 5 liters of lye (pH9.5) or cow urine is added and also 50g of glucose and 25g of sake. All the ingredients are mixed well and left to set for 5 to 7 days. When the surface of the vat hast turned shining with blue bubbles floating, the vat can be used.
The cow urine was supplied by National Taiwan University Livestock Farms, the strong smell of which was really hard to stand. Besides, when kneading the woad balls, they sent out a pungent and distinct smell. However, as everything is new to the audient, they enjoyed themselves very much, especially children. Ms. Chuang Ya-fang of National Taiwan University Highland Farm, National Taiwan University said that the wool used for dyeing came from the adorable sheep at nearby Cingjing Veterans Farm.
The successful experiment on the cultivation of European Isatis tinctoria in the Highland Experimental Farm suggests that the mid altitude mountainous areas of Taiwan is ideal for the growth of woad, which has opened up a new managing way to the mountainous recreational farms. For the people who are fond of indigo dyeing and eager to learn more of this ancient dye, the National Taiwan University’s Highland Experiment Farm will be a good place to visit.