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Method of indigo dyeing

 Method of Dyeing Indigo

Over time, modifications are made to the machinery that won't dye cotton using indigo. 

Warp sheet dyeing, which is being utilised today in significant manufacturing facilities, was created in 1970. 

The steps depicted within the order in the Figure below structure a typical dyeing process for cotton warp. 

Within the pre-treating phase, there are two wetting sections manufactured from roller vats with squeeze rollers or, alternatively, boil-off and rinsing sections. 

There are then six dip vats product of roller vats with squeeze rollers in between these, and above the dip vats are the aerial oxidation stages.

Thanks to a scarcity of space, the illustration only depicts the primary two dip vats and therefore the intermediate overhead airing arrangements. 

Following the last aerial oxidation, the fabric is taken to the after-treatment stage to be washed clean of any remaining chemicals and loose dye. After finishing, the yarn is dried. 

Method of indigo dyeing

Preparation of indigo stock vat

The stock vat is prepared as follows: 



80 gpl

Caustic soda (29.4 M)

130 gpl

Sodium Hydrosulphite

60 gpl

Temperature (wetting)


Time (wetting)

30 minutes

Preparation of dye bath for Indigo dyeing: 

The dye bath is prepared from the stock vat at room temperature using the following recipe: 


Caustic soda

0.5 ml/l

Sodium Hydrosulphite (dehydrate)

1.5 gpl

Stock vat solution ( 3 gpl)

37.5 ml/l

The additions are made within the sequence stated, and therefore the dye bath's hydrosulfite and hydrated oxide concentrations are significantly not up to those of the stock vat. 

While keeping the stock vat at 50°C, the dye bath is kept at ambient temperature. 

Since caustic soda is consumed during the dyeing process as hydrosulphite breaks down, it's also necessary to feature more NaOH during this process, but because each time the stock vat is replenished and added to the dip vat, an excessive amount of sodium hydroxide is continuously added, so only half the calculated amount should be added. 

Three replenishment tanks with liquor metering systems are recommended to permit for continual correction of the dyed cotton yarn's fluctuation in shade and depth of shade of - 

(i) Stock vat
(ii) hydrosulphite solution stabilised with caustic soda
(iii) caustic soda.

A balance between the chemicals and dyes is necessary for achieving a uniform colour. A list of remedies for the aforementioned mistakes is provided below. 

Fault Observed


(i) Greener and a paler shade

(i) Reduce the addition of hydro sulphite or lightly increase or reduce the addition of caustic soda

(ii) Greener and duller shade

(ii) Increase the addition of alkali

(iii) Redder and duller shade

(iii) Increase the addition of hydrosulphite,

Indigo and Denim : 

Denim is sometimes always related to high-design attire. 

The looks of denim are continually changing to satisfy the varied fashion trends and desires of many generations because it's grown to be so widely used nowadays. 

In some ways, fashion trends have revealed how materials and apparel should look, and as a result, denim processing methods have altered. 

Denim may be a twill-woven fabric that's made entirely of cotton. 

The name is believed to own come from de Nimes, the town where it was born. 

The sailors who traded to and from the Italian portion of Genoa, known in French as Genes, and from which the word "Jeans" originated, wore denim trousers and dungarees. 

An immigrant from Bavaria named Levi Strauss saw the demand for tough pants with plenty of pockets during the California Gold Rush.

Thus, the mix of denim, indigo, and Mr Strauss' rivets produced one of the best contradictions within the history of the textile industry: a practical item that served because the cornerstone of a multibillion-dollar industry, proved to be recession-proof, and eventually evolved into a universal garment that cut across all age and time divisions. 

A cotton fabric with a "warp-faced" finish and a 3/1 weave makes up classic blue denim. 

Warp and weft both employ coarse yarn. The weft is left undyed while the warp is coloured solidly, typically indigo. 

The denim fabric is bluer on the front and nearly white on the reverse thanks to its warp-faced construction.

Denim today refers to a good sort of fascinating goods in garments, accessories and embellishments instead of just pants. 

A range of denim textiles could also be produced to fulfil a variety of consumer tastes because of the event of diverse yarn, fabric type, finish, weave, and dyeing options. 

More significance is being placed on creativity throughout the finishing process than on particular products.

Questions -

  1. What is the method of indigo dye?
  2. How to prepare the indigo dye for dyeing the denim fabric?
  3. Explain the dyeing process of denim fabric.


Hussain, T. (2007, November 19). Important considerations in dyeing with vat dyes.; Fibre2Fashion.

Kim, M. R., Kim, H., & Lee, J. J. (2013). Dyeing and fastness properties of vat dyes on meta-aramid woven fabric. Fibers and Polymers14(12), 2038–2044.

Patwary, E. M. Z. (2012, May 4). What is vat dye. Textile Fashion Study; Engr. Mohammad Zillane Patwary.

Saha, S. (2018, October 21). Vat Dyes. Blogger.

Sharmin, F. (2017, November 18). Dyeing of cotton with vat dye. Textile Study Center.

The Editors of Encyclopedia Britannica. (2015). vat dye. In Encyclopedia Britannica.

More about denim fabric and indigo dyeing

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Writer - Rushikesh Patil (Textile Engineer)
(DKTE Society textile engineering college ichalkaranji)
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