Dyeing with Japanese Indigo

Dyeing with fresh Japanese Indigo leaves requires a wee bit of patience, but is completely worth it. Once your plants are mature, you can harvest the leaves several times during the season. If you want to harvest more than once, don’t remove more than one third of the leaves so that the plant can recover.

photo of Japanese Indigo plants


To dye with the leaves, I use Rita Buchanan’s instructions from A Dyer’s Garden. If you want to try dyeing with plant material, Ms. Buchanan’s book is an excellent starting place.

After the leaves have been collected and weighed, the dye must be extracted. The total leaf weight tells you the amount of fiber that can be dyed and the amount of chemicals needed to complete the process. To extract the dye, I fill gallon mason jars with the leaves and warm water and set the jars in a water bath (double boiler). If the water gets too hot during the process, extraction of the dye will fail, so the water temperature has to be monitored
frequently.

Photo of leaves in mason jars before heating

After about an hour, the water turns a bit bluish and the leaves start losing their green
vibrant color.

photo of leaves after heating

After 2 hours, the water bath has reached the target temperature of 160°F and the water
from the mason jars is drained into a larger container. The remaining water is squeezed from the leaves into the larger container. The dye bath is a light bluish color, but is not ready for dyeing.

photo of dye bath before baking soda

Baking soda needs to be added to make the dye bath alkaline. After the baking soda has been put into the bath, oxygen is incorporated by pouring the dye bath from one container into another many times (25 times in this case). This process turns the dye bath into a dark blue-purple. This step converts the precursor to indigo present in the dye bath to indigo.

photo of dye bath after baking soda

Next, thiox (thiourea dixoide) is added to the water to convert the indigo from a bluish form to a yellowish form. The lid is put on the pot, the pot is put into a larger vessel with warm water and is left alone for about an hour. (I used the already-heated water from the double boiler.) After the hour, the blue water has turned into clear, yellowish water under the top film.

photo of dye bath after thiox

Now the dye bath is ready for the fiber. The easy part of dyeing with Japanese Indigo is that the wool does not have to be mordanted, but it does need to be pre-soaked in warm water. (Most natural dyeing methods require that yarn be mordanted, that is, heated in water with a metallic compound that gets the dye to stick to the wool.)

photo of yarn in dye bath

Notice how the yarn isn’t in blue in the dye bath, but the yarn exposed to the air is. This is the coolest part about the dyeing process with indigo. Once the yarn is pulled from the dye bath and exposed to the air, it turns blue!

After several dips in the dye (with equal amounts of time in and out of the dye bath), here are the results.

photo of dyed yarn

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