How Much Indigo in the Vat?

As I learned to use organic indigo vats, I started with recipes from Michel Garcia: “one, two, three”. Michel talks about the vats in simple terms. It’s as easy as 1,2,3. This also represents the proportions of indigo, lime, and sugar that go into the vat:

  • 1 part indigo
  • 2 parts lime
  • 3 parts fructose sugar

It’s simple, right?

Not always.

I probably get more questions about making and maintaining an indigo vat than anything else. There are so many unknowns. It’s taken me a number of years to feel comfortable with those unknowns and to gain the confidence to solve problems with the vat.

I recently had several people ask me about the quantity of indigo in the vat. That’s an important question. Unless you know how much indigo, you can’t really determine how much sugar (or other reduction material) or how much lime.

I’ve watched Michel make vats with very small amounts of indigo and what I would consider very large amounts of indigo. What is the difference? Will you get a darker color from a vat with more indigo?

The answer is “yes” and “no”.

I made 3 small fructose vats with varying amounts of indigo

  • 2 grams indigo per liter of vat liquid volume
  • 5 grams indigo per liter of vat liquid volume
  • 8 grams indigo per liter of vat liquid volume

As you can see from the samples dyed the very next day, there was a great deal of difference in the colors produced from each vat. Even on day 3 there was significant difference. But one week later, the 3 shades of blue are much more similar. All of these samples represent only one 20-minute dip in the vat.

Dye tests done with a single long dip in the three different vats

Why would you use 8 grams of indigo per liter instead of 2 when you can get a similar color from both these options? There is more indigo in the vat, which means more can be dyed over a longer period of time before additional indigo must be added. If I were doing a short-term vat for a small amount of dyeing, 2 grams of indigo per liter would probably be plenty.

The questions to ask are:

  • What  quantity of textiles will  be dyed in the vat?
  • How many people will be using the vat?
  • How long do you want to keep the vat?
  • How quickly to you need to get strong color from the vat?

The coloration of the reduced liquid in the 3 vats is different, indicating varying amounts of indigo in reduction. But the textile is only able to absorb so much dye at a time. We always build up color with multiple, long dips in the vat.

Three indigo vats reduced with fructose: 8 grams, 5 grams, and 2 grams of indigo per liter

The other thing you can see through these glass jars is the amount of sediment at the bottom of the vat. The weakest vat has very little and it gets progressively deeper with the stronger vats. It’s important to keep our textile above this sediment when it’s dyeing.

I currently have a 30-liter vat that I have been using for over a year now. I’ve added indigo to it a couple of times, and of course plenty of reduction material and lime. The vat is still working well but over the months the sediment has gotten very deep, which has reduced my dyeing space so much that it’s time to make a new vat.

The “1,2,3.. ” proportions are guidelines and easy to measure if you’re using fructose. How many bananas or sweet potatoes do you need to reduce 10 grams of indigo? Take a good guess. Making small experimental vats in glass jars has taught me a great deal about how the vat works. We don’t always know but have to start somewhere.

Observe carefully. One must be patient with the indigo vat.