So there are few companies to this day that still actually use natural indigo. This process does not involve the use of toxic chemicals to make the color indigo. The oldest, least labor intensive process of creating an indigo vat was to ferment urine with the indigo leaves. That process is rarely used anymore for special reasons… but to make a natural fermentation vat without harsh chemicals is to create one by fermenting indigo, madder root, bran and washing soda. Basically, with an indigo vat, a fiber will turn blue after oxidizing. It is a very magical thing to watch. The fabric almost looks yellow/green inside of the vat and it only really needs to be held in the vat for a minute or so to pickup color that generally will hold to the fabric. After the greenish fabric is taken out and is exposed to the air, it turns blue. Indigo does not require a mordant, which is what helps other plant dyes attach to the fiber. We will only be using an alum mordant with our other dyes, which is used sometimes in pickling and fertilizing.
Anyways, I want to note and give a high five to those companies that are out there that still use real indigo. There are few in the U.S., many in India and also Japan. This business Pure Blue Japan does a good job of producing very beautiful indigo pieces.
These next few sites are U.S. companies. Truly Organic, uses a number of natural dyes and also, Tinctoria Designs out in Portland uses all natural dyes. ASK Apparel is the business I interned for down in Nashville, TN. They are amazing sisters that dye clothing with their own homegrown dyes. They have a farm out in Bells Bend area where they grow the majority of their dyes.