Dajing Leisure Farm
Wang Kuo-Wei said that the most difficult step is the making the dye which must be fermented. In order to better activate the bacteria, it must be given nutrients. In the past, wheat bran was used, but now glucose and rice wine are used. After fermentation, the branches and leaves are taken out, lime is added and stirred to oxidize the blue pigment so it sinks to the bottom of the pond. After the water is drained, the precipitated blue mud is collected. This is the extraction method of the blue-indigo dye.