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Indigo dye for denim Manufacturing

Dyeing properties and dyeing technique

A dye is nothing but a chemical substance that contains specific colour and when it is applied to the textile fibre or fabric it penetrates inside the structure of yarn or fabric and changes its properties to some extent. 

Dye is chemically soluble in solvents. However, it can be naturally available or it can be made by a certain chemical process which is a synthetic dye.

Changing in colour or in the appearance of fabric with the help of dyes was practised more than 5000 years before.

In the beginning stage, dyes were made naturally or ready to use with less process. The sources of such dyes are animal, vegetable, or mineral origin. The roots, berries, bark, leaves, and wood of plants were used to produce the dyes. 

William Henry Perkin discovered the first organic dye, mauve or aniline, in 1856. Thousands of dyes have been discovered since then.

In the modern age, Synthetic dyes offer a vast range of colours and impart better properties on dyeing even at a lower cost. These dyes soon replaced traditional natural dyes. 

Ease of application, the durability of colour, and resistance to sunlight and chemicals are essential properties considered when selecting a dye for fabric processing.
Ideal dye has suitable colours and all fix itself on the surface of the fabrics. 


It has fastness properties, such as Fastness to light, Resistance to the action of water, diluted acids, alkalis, and various organic solvents used in dry cleaning.

Indigo dye

  • Denim fabric is almost dyed fabric of indigo dye.
  • Since the denim fabric was invented, the indigo dye has been associated with it. 
  • Indigo dye is a natural plant-based dye. The plant of this dye was found in Egypt, Babylon, Greece, Rome, China, and India. 
  • From the 11th century, indigo plants were cultivated in Islamic Spain. 
  • In the modern era, plant dye has been replaced by chemical indigo dyes that are easier to manufacture.
  • Nevertheless, indigo is unique in its ability to impart surface colour due to partial penetration into the cotton fibres. 
  • When the indigo-dyed cotton yarn loosens, the inner layers remain uncoloured.
  • The chemical formula of indigo is C16-H10-N2-O2. 
  • Indigo dye is a dark blue crystalline powder that sublimates at 390° – 392°C (734–738 °F). 
  • Indigo dyes are not soluble in water, ether, or in alcohol, but are instead soluble in nitrobenzene, chloroform, and concentrated sulphuric acid.
  • The unique feature of indigo-dyed denim is that it can achieve washing effects on repeated washings without losing colour freshness. 
  • Another important feature of indigo is that, unlike many other dyes, denim-dyed indigo does not pose health risks.
  • Technical features of the indigo dye include the ability to dye at room temperature, preferred shades from black to dark blue that is not very glossy, and the low indigo solution is not sensitive to water hardness—this allows for a grey dye or minimal pre-treatment of the cotton, and repeated washing removes the dye slowly without losing its freshness.

DSPAT Indigo dye
Indigo dye

Vat dyeing process

Vat dyes are a class of dyes that can be done in wet foam, the term vat dye is used to describe a chemical class of dyes that are applied to cellulosic fibre (i.e. cotton) using a redox reaction process.

Vat dyeing is a process that refers to dying that takes place in a bucket or vat. The original vat dye is indigo.

Vat dyes are generally obtained only from plants but are now often produced synthetically.

With the help of the caustic soda and the appropriate pH value of the dye bath, the vat dyeing process is possible.

wool cannot be dyed using vat dyestuffs, because wool is soluble in caustic soda solutions.

Exhaust dying process

Exhaust dyeing is also known as the batch dyeing process.

In this method, the penetration of dye from a dye bath to the textile material happens in the same piece of equipment.

The various methods of batch dyeing result from the type of machine used in the dyeing process. 

Common machines used in the batch dyeing process include the jigger dyeing machine, winch dyeing machine, jet dyeing machine, and beam dyeing machine.


  1. What are the properties of dyes?
  2. What are the techniques of dyeing?
  3. What is indigo dye?
  4. What is the vat dyeing process?
  5. What is the exhaust dyeing process?


Hakoo, A. (2021, May 9). Denim fabric weaving - the manufacturing process, methods, and technologies. Textile School.

Pipon, M. (2020, August 7). Manufacturing Process of denim garments. TEXTILE VALUE CHAIN.

Sarkar, P. (2017, June 4). Denim fabric manufacturing process –the learner’s guide. Blogger.

Shaikat, N. M. (2018, September 17). Denim Manufacturing Process, Types and uses [updated]. ORDNUR.

Types of denim fabric used in garment manufacturing. (2015, August 1). Garments Merchandising.

What is Denim Fabric: Properties, How it's Made and Where. (2019, November 11). Sewport.

Wikipedia contributors. Denim. Wikipedia, The Free Encyclopedia.

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