Here is the indigo vat recipe that I have been working with written by Earth Hues. They are a wonderful company supporting agriculture, natural color and artisans around the world. I order my pigment from them and every time I order, I ask where the pigment is from. Most of the time the pigment has been from El Salvador. This is the recipe they provide and it's fantastic!
// Avocado pits and skins chopped up and put into the freezer. when ready, put into large glass jar, with 1 part ammonia and 2 parts water. let ferment for a week. shake jar from time to time and dye! amazing color!!!