Here are three of my old cotton tablecloths that I have waxed and painted. The one on the left is the cutch/iron dip dye project, the middle one has been painted with weld, and the blue purple one is an indigo-cochineal combo. I'm planning to put them all into indigo, hoping for black, chartreuse, and purple respectively.
When the indigo pot looks blue, it isn't ready to dye anything. Indigo is only soluable in water in the absence of oxygen. All the oxygen must be removed from the pot before the fiber is added. While it is immersed in the liquid it picks up indigo, which solidifies and adheres to the fabric when it comes out into the air.
I remove oxygen chemically, by adding thiourea dioxide. The traditional method is to compost it out. You have to feed your indigo pot over several weeks, kind of like sourdough starter, but it takes much more time and attention than I have to offer so I take the short route. Most indigo is composted out of its host plants, so it has a distinctive odor. Fortunately, it doesn't linger on the fabric. When the oxygen is gone the pot turns yellowy green. When placed in the indigo, the fabric also looks green, only turning blue once you pull it out. The metamorphosis happens right before your eyes just like magic.
Another element of indigo dyeing that must be controlled is the pH. Indigo must be highly alkaline to work properly.
This is my third attempt to get these pictures in, so I am going to quit now before I lose them again. I will show the results tomorrow. I HATE DIAL-UP.