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Iron Vat "How To" with a Video!

Nil / Neel (Bengal / India)
Xiquilite (Mayan blue, Central and South America)
Ai (Japan)
Aro (West Africa)
Nila (Malaysia)
Indigo works like no other natural dye.  It has its own rules. From a variety of plants containing the right properties, the fresh leaves are collected, go through a process of fermentation and aeration in alkaline bath, that results in the settling of the indigotin settling creating a sludge that is then collected and dried. This is indigo dye, C16 H10 N2 O2. Phew. But we are not done yet!

To dye with, your indigo will still need further help. 
You must remove the O2 from the compound, so that it will bond to your fiber.  This is called “reduction” and it converts the indigo into "white indigo" (leuco-indigo) which is actually green. In this reduced green state it will bond to natural fibers only and once exposed to oxygen again, it will turn blue.  To reduce you must have a perfectly balanced vat of indigo, alkaline, and reducing agent. 

There are many combinations that people throughout time have figured out how to do this.  Henna powder, Ferrous Sulfate (Iron) or Fructose (sugars from ripened fruits) are just three ways to reduce, and Calcium Hydroxide (Lime) is one alkaline to use.


*Always wear a dust mask or at least a bandana when mixing your powders.  Lime is alkaline and can be an irritant to your eyes, nose and throat.  Please use with caution.
*I use tap water (sitting out to air) here in NYC and haven’t had any issues.  But many will use distilled or collected rainwater to avoid having any additives getting in the way. Especially if you have hard water.


  1. Bring water to nearly boiling in a stainless steel (or ceramic coated) pot and keep at 180 degrees, but no higher.  If you want to transfer the water to a heat resident bucket, so you can store it easier, then transfer when you are ready to start adding the ingredients.
  2. Hydrate your indigo using marbles if necessary (refer to above directions). Have your lime and fructose or iron set just aside, ready to grab. You’ll have to wet your henna, adding hot water to make a sludge, as it’s a little insoluble.
  3. Create a whirlpool with a dowel, wand, or rod (not a spoon as it makes too many bubbles). I use my left hand to stir so I can grab the ingredients and add with my right hand. 
  4. Add your hydrated indigo, then iron or fructose or henna, then very carefully lime because it will fly about if you do not delicately let it fall into the vat. Wear a mask! I find dumping it quickly and completely is best. Then slowly stir until it’s dissolved.
  5. Once mixed through, stop stirring and bring the stirring rod around the edges going the opposite direction to stop spinning, creating the flower.
  6. Let vat settle for 30- 60 minutes before dyeing, doing a dip test before getting into the process. 
  7. If leaving overnight make sure you seal with an airtight lid.  I always have a scrap piece of plastic sheeting around to lay on top of the vat and then place a lid on top.  Silicon lids work great because you can push them down to the surface of your pots and then lid them. Ferrous vats can cool and you can dye with them in that lower temperature.  Fructose and Henna vats need to be brought back to temperature when you’re ready to dye. 120-140 degrees (protein fibers like the higher temp)

  1. Wet fabric, bundled or not, before dyeing. All fiber should be fully saturated (not dripping wet) when dyeing.  Clear the surface of the vat.  Remove your “flower” (undissolved indigo and air bubbles) and keep aside so you can add it back to the vat when done dipping). Many dyers leave a piece of wood floating on the surface to push away the coating on the surface. Carefully submerge you fabric and hold under the surface about an inch, moving slightly and massaging, for at least 5 minutes. Larger bundles can require 30 minute dips 
  2. Remove fabric by squeezing under the surface, lifting gently off to the side of your vat.  Do not splash into your vat, as this will introduce oxygen and you will have to “reduce” it again, waiting up to an hour.  
  3. Let your fabric breathe by letting it see the air to turn from green to blue.  Some will dip the fabric in cold water to oxidize and clean off the heavy spots of indigo.  This is especially helpful with a ferrous vat where there can be a lot of sediment.  Oxidizing in water you will get a cleaner, more even look, and it also helps oxygen to get to the tough to reach inside a fold of shibori folded pieces.
  4. Continue to dip your piece this way until desired blue is achieved.  You must layer indigo to get the darker shades. Time submerged in the vat has little to do with saturation of color, but more the proper bonding time.  The deeper shades are from more times dipped and exposed to the air, then dipped again.  If there is any green left on your piece, and you dip again without waiting for it to turn, it will not get any darker. Remember your fabric will look darker when wet, so dip one or two times more, when you like the color your piece is. When you’re ready to wash, you don’t have to wait for it to turn blue, as the washing will help it to oxidize.

Rinse in cold water to remove a good amount of indigo.
Fabric should then be soaked in white vinegar bath for 15-30 minutes, to deactivate the reducing agent and it also helps set or “fix” the indigo. (1 cup per gallon bucket)
Soak in hot water for at least one hour or overnight.
Wash in hot water and mild detergent like dove or dr. bronners, but synthrapol is highly recommended.  It helps with dye bleeding by suspending dye particles. Rinse in cold water.
During the life of  your piece, continue to wash your piece in cold water and avoid intense, direct sunlight.

Vats can be kept for years if used daily, and cared for.  You shouldn’t store a vat for more than 6 months unused. Stored vats can be brought back up to temperature and then pH tested and adjusted with reducing agent and alkaline.  There is a finite amount of indigo in your vat, and it needs to be added the more you dye.  You will notice your blues will become lighter the more you dye with it.

Keep your vat as long as you can, but when ready you should neutralize before pouring down the drain. Adding vinegar will do the trick but also whisking vat to add air, turning the lime into calcium carbonate aka chalk/limestone, will make it safe enough to compost.


All natural dyers have to find their own way to a routine.  The more you dye and work through issues, the closer you are to finding that rhythm.  Most importantly, have fun! 


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