Introduction
You can choose to reduce with chemicals (Sodium Hydrosulfite and Sodium hydroxide) or natural items like Oaktree ash. The former is easier and suitable for beginners but the latter is 100% natural and traditional but very difficult.
1. Using Sodium Hydrosulfite (for 20 liters of the liquid)
Please do this in a place with good ventilation.
① Put 2kg of the Sukumo indigo in 5~6 liters of water and let stand for about 6 hours, then please discard the brown water with a filter cloth. After this process is repeated twice, add 160g of sodium hydroxide and leave it for one night.
② Add 20 liters of hot water and 80g of Sodium hydrosulfite to ① and mix well until the mixture becomes sludgy. Then, please cover it with plastic wrap, and let stand for a day. During this time, the liquid should be stirred two times. After that, you can get the Sukumo indigo liquid.
2. Using Oaktree Ash (for 10 liters of the liquid)
Indigo dyeing with a indigo liquid made from Sukumo and tree ash is called "発酵建て" (fermentation reducing) or "地獄建て" (hell reducing) in Japan. The whole process is a bit difficult as it takes about 10 days but all the ingredients in this process are natural and traditional. It involves the following four steps.
① Place 1 kg of Sukumo in a large bucket and add 500 g of oak tree ash into it.
Pour 10 liters of hot water (70-80°C) and stir the bucket with a stick for 5 min.
② The surface of the liquid foams up, but the color of the liquid is brown then.
③ Stir the liquid every day for a week. After that, the color of the liquid will become closer to blue.
④ If large bubbles form on the surface of the liquid, you can dye with it. The liquid can be used for up to six months.
