The color indigo is part and parcel of our lives – as much as jeans are. Think of denim and what comes first to our mind is the beautiful indigo shade of the fabric. The indigo color that you see on denim fabric (warp thread of denim fabric is dyed to indigo color) is a result of a chemically synthesized indigo dye, but initially, indigo dyeing was only done with natural extracts from plants.
You can dye your clothes to a beautiful indigo blue with natural indigo dye or synthetic indigo dye. Synthetic indigo has a molecular structure similar to natural indigo. Both can be used to dye cotton, linen, wool, viscose, and silk
Natural indigo dye is a water insoluble pigment and has to be made soluble in water with the help of a variety of alkalies and agents.
Natural Indigo Dyeing
Where does the color indigo come from?
The indigo dye is extracted from the leaves of several plant species grown across the world – they all have one thing in common – the indican molecule.The dye produces deep shades of indigo when used repeatedly in dyeing and with exposure to oxygen in the air.
Plants of Indigo dyeing
The most important plant species for indigo dyeing is Indigofera tinctoria, which is native to India. Plants of the species Storobilanthes are also used in Indigo dyeing. Another plant giving this deep shade of blue is Indigofera suffruticosa.
Polygonum Tinctorium is the indigo plant used in Japan. Indigo Dyed fabrics are called ai-zome textiles in Japan.
Till the time this dye reached the western shores, Europeans got their blue shade from woad, Isatis tinctoria, which contains the same indigo molecule.
You can buy natural indigo dye or make the dye from the leaves of the plants. Cut the leaves from the plant, boil them in water in low heat for a long time. The leaves are left to ferment for days. You can store this dye solution and use it when needed.
Natural indigo dyeing is different from dyeing with other natural dyes out there. It is not a simple ” simmer, stir and dye” dye. It needs a chemical reaction for the dyeing to take place. The color of your dyed item turns blue only when it is exposed to oxygen.
For getting the deep shades, you have to repeat the dyeing and oxidizing several times. You can get more than 30 shades of this blue color. And once the dyeing is done, the color is very colorfast.
Related post: Tie dye spiral patterns
How is Indigo dyeing complicated?
Indigo dyes are Vat dyes which means they are insoluble in water (or most other solvents) but they become soluble during the vat-making process. These dyes need to be immersed in an alkaline solution and fermented to remove the oxygen to obtain a soluble form. When the dye reacts with oxygen later in the dyeing process the indigo blue color is obtained as a result of the oxidation on the fabric. That means dyeing with indigo is more complicated than dyeing your fabric with other dyes
Many alkalies and agents are used in the vat making process of Indigo dye – to reduce the oxygen and help make the vat dye soluble in the water. In Japan agents like wheat bran, hardwood ash, lime, and sake are used in the natural dye making. Sodium hydroxide and soda ash can also be used. Soda ash is also known as sodium carbonate or washing soda. Sodium hydroxide is also known as caustic soda. After the vat is made and dyeing is done, the fabric is exposed to air and the oxygen present in the air turns the dye into insoluble blue color – the ever familiar indigo blue color.
Checkout a video with details of the process.
The oldest fabric dye in indigo color has been discovered in Peru – this is more than 6200 years old. You can read about this cloth here.
Related posts: Types of Fabric dyes.; Steps to dye clothes/fabric; How to do basic tie and dye techniques; Make Easy patterns with tie and dye; How to tie and dye a t-shirt
