Indigo dying is tricky.
There are some tribes in Africa that seem to be doing it the no-nonsense way. They take the indigo leaves and pound the pigment directly into the cloth with a small club. This is the smart way to avoid the hassle of removing the oxygen from the dying liquid either chemically of through fermenting. If one of the oxygen molecules in the pigment chemical equation is not removed the indigo will not stick to the cloth.
A fermentation type vat gone wrong is the foulest thing that can happen to a natural dyer. Putrid gas. And things can go wrong very quickly. You start with the vat only one tenth full of high pH water from either seeping ash or with slaked lime. Each day you add a bucket or so. When the indigo compost starts to ferment you add a cup of sugar source to just bring the good bacteria over the edge and to bloom. Too early and it burns out without reaching a kind of critical mass and too late it goes bad. (The whole process is kind of sexy come to think of it.) One time I was stupid enough to add a cup of sugar dissolved in tap water that contained chlorine. I should only use water from the stream next to the house.
In an hour the sharp healthy ammonia smell turned to putrid rotten swamp gunk. It could be salvaged with a chemical reduction agent. The color was fine but the smell was foul.
The recent stink was simply caused by a build up of slaked lime and hydro-sulphate reduction agent building up at the bottom of the vat. The hot summer weather starting it stinking and the smell in whatever form it took just couldn't be eliminated.
Like Velma said, the smell in the dyed clothing can be gotten rid of in one hot water wash.
The indigo bubbles on the surface of the indigo tell you the condition of the vat. If they are purple and oily looking there is enough actual pigment in the water. If they are clear and light blue and slightly frothy you need to add pigment. If the liquid just under the surface is not yellow green that is telling you that there is too much oxygen in the vat and needs to be removed.
If you get to know the sound of a stick hitting the inside wall of the vat you can quickly judge the pH level. A low 'thung' means a low pH. A higher 'ting' means the pH is about 12 where it should be. It takes a few years to get really good at reading the signs in the bubbles and the smell. It starts to get like palm reading when you notice lines and milkiness etc and other finer nuances and their meanings as you understand the vat over years.
Indigo dyed good are often attributed with keeping insects and snakes away, stopping athletes foot, and generally being good for you. I wonder.... I've gotten bitten many times while working at the dye vat and a somewhat doubt the poisonous mamushi around my place could care less what I am wearing. If I really annoyed them I'm sure they woud bite no matter what.
I do think that the bacteria on newly dyed indigo clothes from a pure natural fermentation vat might be healthy but I doubt the indigo pigment has any health benifits.
The color itself is another story. As a natural dye it is gentle to look at and vibrates at a pure frequency. This is good for anyone. Pure and simple.
