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Alkali desizing

Classification of Desizing methods

The desizing process of the fabric can be classified into main three categories, as per the chemicals and methods are subcategories. 

Desizing methods

A) Hydrolytic methods

B) Oxidation methods

C) Novel methods

A)Rot steep

A) Chlorine

A) Solvent

B)Acid steep

B) Chlorite

B) Desizing 2000

C) Enzymatic 

D)Alkali desizing


C) Low-temperature plasma treatment

Among hydrolytic desizing processes, alkali designing is discussed below.

Alkali desizing

Alkali solutions are utilized in the industry because acid desizing is a significantly more expensive procedure.

To hydrolyze starch, use a 2-3 percent solution of an alkali, such as NaOH. The fabric is squeezed and stored for 4-6 hours after being padded in the alkali solution.
After that, it's rinsed in hot water thoroughly before being cleansed in cold water.

Advantages -
1. scouring action is done simultaneously so, does not requires a separate scouring operation.
2. Process is faster than the rot steep method.


1. It is a very expensive process due to the use of chemicals like Alkali.
2. There is a risk of degradation of the fabric due to local drying as well as alkali.
3. The efficiency of alkali desizing is also very less than acid desizing.
4. Weakening of cotton is possible if proper precautions are not taken.
Alkali desizing process layout
Alkali desizing process layout 

Special precautions are taken to avoid fabric contact with air- 

Because starch hydrolysis is an exothermic reaction, the temperature of the cloth rises as the reaction progresses, occasionally reaching 50°C. As a result of this rise, we must use caution when using weak mineral acids.

In a closed environment, weak mineral acid at 50°C (in the aforesaid conditions) will not hydrolyze cotton cellulose, and the fabric will not 'tender' as a result of the desizing process.
This precaution must be taken to ensure that the acid does not harm the cloth.

Local evaporation of water from the liquor will occur if the acid-impregnated material is not properly closed, especially in regions that are open to the outside air.

Effect of Higher concentration acid taken or strong acid use- 

The fabric's cellulose will be hydrolyzed if the acid concentration is higher or more powerful acids are used.

As a result, the fabric will degrade in random places, causing uneven degradation.
When uneven dying or printing happens, this damage is usually found much later, during the dyeing or printing process.

Desizing action at micro level
Desizing action at the micro level

Questions -

  1. What is alkali desizing?
  2. What are the advantage and disadvantages of alkali desizing?
  3. What are the precautions that are taken to avoid fabric contact with air?
  4. What is the side effect of using highly concentrated acid on fabric for desizing?


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Further reading,

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