Indigo is a magical plant. It produces the denim blue that we associate with blue jeans. In fact, your Levis were originally dyed with indigo. Often that indigo in the jeans would “crock,” meaning the blue would rub off on your skin until that extra dye was removed from many washes.
There is a variety of indigo native to Texas, but most varieties will grow here. The leaves can be used fresh or frozen to dye, but that would usually be for small projects.
In India, the harvest goes through an extraction process in which the leaves are fermented. The fermented product is formed into balls or squares (cake) and dried. This hard indigo then has to be powdered before one is able to dye. It sometimes takes a hammer to do this–ask me how I know!
Indigo can also be composted The plants may be dried, then stomped to break up the leaves and stems before composting. Rowland Ricketts has some great pictures of the process on his website. A little interesting tidbit—The Ricketts were winners in Martha Stewart’s Made in America contest.
Before dyeing, the indigo must be prepared by reducing the oxygen so that the element that actually does the dyeing is released. There are several ways to do this, but the only one I have used is with chemicals of lye and thiourea dioxide. Other methods are more friendly and use things like mango peels or wheat bran along with lime to reduce the indigo vat. That’s the method I’m going to learn next.
Now for the magical part of indigo. After all the ingredients are mixed with the indigo powder, you wait for the chemical process to complete. When the dye vat is ready, a coppery sheen develops on top. The liquid below is kind of a weak yellowy green. The cloth or yarn is carefully lowered into the vat and let to rest for a few minutes. Then the item is carefully removed, trying not to introduce oxygen into the vat in the process. When the cloth comes out of the vat, it is that same yellowy green as the liquid, but as it is exposed to the oxygen in the air, it gradually changes to that famous indigo blue. It’s magic! But it’s also an art. To me it’s kind of like cooking; you just know when it’s right.
You Tube video about indigo process
Another You Tube video about process