At Archivist Studio we create most of our pieces from white or cream colored luxury hotel bed linen. In order to offer more colors on the spectrum, we researched natural garment dyeing methods. One of the methods that we are now applying is dyeing with the plant-based pigment indigo. In this article you will find more information about natural indigo dyeing and we will teach you how to do this at home. 

Historically to give fabric a blue shade, the plant derived “indigo powder” was used. The most widely used plant for indigo is the Indigofera Tinctoria. It grows best in warmer or even tropical climates. Since 1897 indigo has also been produced synthetically, from petroleum. To this day this synthetical indigo is used on a large scale for the denim industry. 

Indigo can dye all natural fabrics (protein fibres like silk and wool or cellulose fibres like cotton and viscose). However, by itself the powder does not adhere to fabric, it has to undergo a chemical change to become water-soluble. To do this you have to build a “vat”. This is a combination of water, indigo powder, slaked lime (calcium hydroxide) and fructose. There are multiple “recipes” but this organic recipe is according to our experience the easiest one to build at home. 

What you need:

Equipment

• A 5 liter glass or plastic sealable pot (has to be able to withstand boiling water)
• Stirring stick
• Empty water bottle with cobbles (you can use cobbles with a 1 - 2 cm diameter and  fill half of the bottle with it. 
• Scales to measure
• Protective gloves, glasses and mouth mask. 

Ingredients

• 30 g (1 oz) powdered natural indigo
• 90 g (3 oz) fructose powder (what athletes use as a supplement)
• 60 g (2 oz) slaked lime or calcium hydroxide (can be bought at online chemical solvents sellers)
• Some vinegar for the aftercare of the fabric. 

Building the vat:

1. Put the indigo powder in the cobble filled bottle and add some hot water to it. Shake vigorously to turn the indigo in a paste. This process is essential, as it “wakes up” the indigo molecules.
2. Fill the pot with ¾ of hot water (boiled water).
3. Add the fructose and stir to dissolve. This is the reducing agent, it removes the oxygen from the water which allows the indigo powder to reduce to its water-soluble form.
4. Add the indigo paste and stir carefully. 
5. Add the slaked lime, to increase the pH of the vat. Stir carefully without creating air bubbles as you want to avoid oxygen coming into the vat. Oxygen is the biggest enemy of your vat, once oxidized the vat stops being effective and ultimately will not dye your fabric anymore. In step X you will find tips on how to bring your vat back to life. 
6. In about an hour the vat will be ready for dyeing (you can stir the vat every 15 minutes). It will develop a bronzy layer on top which is called “the flower”. The interior of the vat should be a clear green. In the meantime keep the lid of your pot closed, to make sure the oxygen stays out. 
7. Depending on how big the fabric is that you want to dye, you might want to move your vat to a bigger pot. Fill your bigger pot with boiled water and gently lower your smaller pot with contents in the bigger pot to make sure it mixes without too much splashing. Allow this bigger vat to mix for about an hour. 

Dyeing your fabric:

1. Either scour your fabric (boiling it for 10 minutes in water) or soak your fabric well (at least 15 minutes in lukewarm water) to make sure the fibres are well hydrated and are soaking up the indigo.
2. Move the flower aside and dip a piece of fabric in the vat. You can leave in there for 30 seconds to 10 minutes). 
3. Oxidize the fabric by hanging it in the air or rinsing it in cold water. When fully oxidized it will be blue. 
4. It is good to experiment with the dipping time but mostly the darker intensities are being reached by dipping and oxidizing multiple times. 
5. At some point your vat will be “exhausted”. Either because the indigo has been fully used (this is also when you can achieve the lighter hues), when the pH has altered (for protein fibers 9 - 10  and for cellulose fibres 11 - 12 is ideal) or when too much oxygen has slipped into the vat. Your best chances are to create a new smaller vat and to add that to your old vat. Or read this extensive guide with many tips to create a long lasting vat. 
6. Once you have reached the color intensity that you like, rinse the fabric well (preferably in water with some vinegar to reduce the pH levels). You can also wash the fabric in the washing machine, make sure you wash it with similar colors.

Indigo dyeing is such an interesting journey. If however you want to wear a naturally colored blue garment without all the fuss, we would love to refer you to our hand dyed indigo pieces. If you would like to have a more in depth read on all the different indigo recipes, we recommend this guide.