Original post appears on Virtue + Vice | News.

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This year I am extra excited about Fashion Revolution Week because of the event virtue + vice is hosting at Brand Assembly on April 25th. We have put together an interactive DIY and networking event where we will be dyeing scarves with natural indigo using traditional Indian Bandhani techniques. If you haven’t signed up already, you can here.

As some of you know I split my time between Goa and NYC, and because of that, I am a member of both Fashion Revolution country teams. This event is so special to me because it is the first USA x India cross-country collaboration!

did you know it takes almost 1 week to prepare natural plant-based indigo dye?

Because of this, the dye needs to be prepared before the event on the 25th. Don’t worry about missing anything cool, you can check out our behind the scenes, pre-event dye preparation here with an explanation of the science used.

the kit

Botanical Colors organic indigo dye kit

For the event, we are using Botanical Colors Natural Organic Indigo. The kits include pre-measured organic plant-based indigo, fructose, calcium hydroxide, also known as pickling lime, and small pebbles and string for creating bandhani designs.

What is not included, but can be easily picked up at a local hardware store:

a 3 gallon bucket with an airtight lid

a stick to stir the stock and vat with

a 1 quart measuring cup for water

There are two parts to preparing the indigo, and each part takes about 3 days, the first is preparing the stock, the second is preparing the vat.

preparing indigo

step 1 – indigo powder

natural organic indigo powder in a bucket is so dark it looks almost black

Empty the contents of the indigo packet into the bucket. Natural indigo powder is so dark, it is kind of like that impossible shade where you can’t tell if it’s black or really dark navy.

step 2 – wet the indigo

making indigo paste the indigo dye needs to be mixed to absorb the water

Add a tiny bit of water just enough to wet the indigo and create a paste. Indigo, unlike many other types of dye, is not water soluble but, it can absorb water. You can see in the photo how the indigo and water don’t naturally combine, but with a little mixing, the indigo will start to absorb the water and a paste will form.

mixed indigo paste

When the paste is ready it will look like the second photo. A little chalky and clumpy, but mostly mixed in uniformly.

step 3 – add water

mixing in water to indigo paste

Next add about 3 quarts of water to the paste, slowly, and make sure to keep mixing as you add the water. As the indigo becomes more diluted the color will turn from blackish to more of a blue.

why do we need to make a paste before adding the rest of the water?

Have you ever baked a cake and accidentally added all the flower in all at once, then no matter how much you stirred and stirred there were still lumps? That’s kind of the same idea here. Because the process of making paste wets the indigo, it makes it easier for the rest of the water to be added without clumping.

 step 4 – add a base to make the solution alkaline

adding carbon hydroxide to indigo

Next, a base is needed to make the mixture alkaline. By adding in the calcium hydroxide, we get our first chemical reaction! Safety tip, you might remember this from high school chemistry class, when mixing chemicals it is important to add dry to wet, never the other way around.

Carbon hydroxide is used in the reaction to make the stock alkaline. The alkalinity will help to dissolve the indigo.

Go slow with this part. As the reaction starts to happen the bucket will become warm, and if you go too fast the indigo could bubble up and overflow. I added in about 1 heaping tablespoon at a time and mixed thoroughly before adding the next tablespoon.

melanie disalvo wearing a dust mask to protect from stray particles of carbon hydroxide

Carbon hydroxide in large quantities (I am making enough dye for 50 people!)  can be an irritant to the lungs and eyes, it’s as fine and puffy as powdered sugar, so I used a dust mask to protect me from any stray particles.

step 5 – add fructose to reduce

adding fructose to indigo to start reduction reaction

Once all of the carbon hydroxide has been added to the mixture,  start adding the fructose. Fructose is used to get the process of reduction started by removing oxygen. You will know it’s working because bubbles will start to form on the surface like in the photo above.

Add the fructose the same way the calcium hydroxide was added – very slowly, spoon by spoon, mixing after each spoonful.

As the fructose is added to the solution it may become thicker, this is called indigo mud. If indigo mud starts to form, just add more water. For this batch, I needed to add about another quart of water.

step 6 – let it sit

indigo is ready when there is a reddish metallic film on the top and is a yellowish green on the edge with an indigo bloom or bubbles

Let the stock sit for about 30 minutes to 1 hour. You will know the reaction is happening and you are on your way to an amazing indigo vat when a thin, mirrory, reddish film starts to form on the surface and the sides of the vat start to look a yellowish green or teal. Looks pretty, right?

step 7 – wait at least 3 days

the indigo is ready when it is an amber or yellowish color

Cover the bucket and let it sit for the next 3 days. Remember to stir the mixture once a day. This batch I made needed a little extra fructose to finish the reduction process. If you are having problems with your stock Botanical Colors is a great resource to reach out to for help! You will know your dye is ready when it separates and the top is a clear amber green like this. I spooned out a little from the top because it is hard to see in the bucket.

step 8 – test the dye

leave fabric in vat for 10 minutes to test

First, wet the fabric you want to dye, and wring it dry so it is damp. Then dip the fabric into the dye, wait about 10-15 minutes.

step 8 – let the dye oxidize and dry

indigo looks yellowish green when it first comes out of the vat

When you first take the fabric out of the vat it will be yellowish green, like in this first photo.

as indigo oxidizes is turns from yellowish green to blue

Here, in the second photo, you can see how the test strip has turned blue from oxidation. It takes about 10-15 minutes for the dye to oxidize.

step 8 – add more water to the vat

Adding more water will dilute the vat. Now, to get the same color as your test strip you will need to dip multiple times. The best indigo is a slow process of multiple dips with oxidations in between each dip. Some professional dye ranges dip anywhere from 5, to as many as 12 times.

Tip: the longer you let your prepared vat sit the stronger the dye will become.

meet our makers

learn how we make our indigo fabrics in India in 12-footwells!

Shop Virtue + Vice on Jewel & Lotus

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Original post by Virtue + Vice | News can be read at https://shopvirtueandvice.com/blogs/news/how-to-diy-natural-plant-based-indigo-vats.

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