If you can stand the smell, a urine vat is the way to go for dyeing with Indigo. The process is quite simple: First, you collect a jar of urine. The more concentrated the better, so drinking lots of water, alcohol, or caffeine to increase production isn't advisable. Add the natural indigo to the urine, close the lid, and keep it in a warm location. I put mine outside with a 60 watt light bulb on it and partially cover the jar with a towel. This works fine for the climate I'm in. For the first few days it's necessary to reach in with a gloved hand and break up the clump of indigo. Be careful to not agitate the liquid as you don't want to introduce oxygen. When the solution is sufficiently reduced you'll see a coppery film on the surface as in the first photo. You are now ready to dye! Wet your fiber and gently introduce it into the vat. With your gloved hand, lightly massage the fiber for about fifteen minutes.The fiber will be a yellowish-green color inside the jar but once it contacts air, it will oxidize to dark blue. Separate the fiber/yarn well so that it can oxidize completely and let it rest for about thirty minutes between each dip. You can dip as many times as your vat will allow though mine usually gets 'tired' after about four dips. A way to tell if your vat is tired is to dip a small piece of cotton. If it looks gray after it has been rinsed in water, then you should stop and give the vat several days to reduce again. From time to time you'll need to add more indigo and/or urine but a vat should live for many years.