What is desizing? | Desizing of natural fabric:

Desizing is done in order to remove the size from the warp yarns of the woven fabrics. Warp yarns are coated with sizing agents prior to weaving in order to reduce their frictional properties, decrease yarn breakages on the loom and improve weaving productivity by increasing weft insertion speeds. The sizing material present on the warp yarns can act as a resist towards dyes and chemicals in textile wet processing. It must, therefore, be removed before any subsequent wet processing of the fabric.

Desizing of natural fabric
Desizing process


Natural sizing agents

Natural sizing agents are based on natural substances and their derivatives:
  • Starch and starch derivatives: native starch, degradation starch, chemically modified starch products
  • Cellulosic derivatives: carboxymethylcellulose (CMC), methylcellulose, oxyethylcellulose
  • Protein-based starches: glue, gelatin, albumen

Synthetic sizing agents

  • Polyacrylates
  • Modified polyesters
  • Polyvinyl alcohols (PVA)
  • Styrene/maleic acid copolymers

Desizing processes


Different methods of desizing are:

  • Enzymatic desizing.
  • Oxidative desizing.
  • Acid steeping.
  • Rot steeping (use of bacteria).
  • Desizing with hot caustic soda treatment.
  • Hot washing with detergents.

The most commonly used methods for cotton are enzymatic desizing and oxidative desizing. Acid steeping is a risky process and may result in the degradation of cotton cellulose while rot steeping, hot caustic soda treatment and hot washing with detergents are less efficient for the removal of the starch sizes.


Enzymatic desizing consists of three main steps: application of the enzyme, digestion of the starch and removal of the digestion products. The common components of an enzymatic desizing bath are as follows:
  • Amylase enzyme
  • pH stabiliser

Enzymatic desizing

Enzymatic desizing is the classical desizing process of degrading starch size on cotton fabrics using enzymes. Enzymes are complex organic, soluble bio-catalysts, formed by living organisms, that catalyze chemical reaction in biological processes. Enzymes are quite specific in their action on a particular substance. A small quantity of enzyme is able to decompose a large quantity of the substance it acts upon. Enzymes are usually named by the kind of substance degraded in the reaction it catalyzes.
Amylases are the enzymes that hydrolyses and reduce the molecular weight of amylose and amylopectin molecules in starch, rendering it water-soluble enough to be washed off the fabric.
Effective enzymatic desizing require strict control of pH, temperature, water hardness, electrolyte addition and choice of surfactant. 

Enzymatic desizing offers the following advantages:


  • No damage to the fibre.
  • No usage of aggressive chemicals.
  • Wide variety of application processes.
  • High biodegradability.

Oxidative desizing

Oxidative desizing can be effected by hydrogen peroxide, chlorites, hypochlorites, bromites, perborates or persulphates. Two important oxidative desizing processes are: the cold padbatch process based on hydrogen peroxide with or without the addition of persulphate; and the oxidative pad steam alkaline cracking process with hydrogen peroxide or persulphate. The advantages offered by oxidative desizing are supplementary cleaning effect, effectiveness for tapioca starches and no loss in effectiveness due to enzyme poisons. Some disadvantages include the possibility of fibre attack, use of aggressive chemicals and less variety of application methods.


Acid desizing

Cold solutions of dilute sulphuric or hydrochloric acids are used to hydrolyze the starch, however, this has the disadvantage of also affecting the cellulose fiber in cotton fabrics.