Garment Wet Processing

Garment wet processing involves various treatments of garments in a wet state.  There are starch materials is present in the fabrics of the new garment which are stiff in hand-feel and need to be removed to create a better hand feel and comfort. The softness /hand-feeling of garments could be further increased and washed garments could be worn directly after purchase from the store. Like in Garment dry processing, here the aim is also to create a worn look. Fading effects are produced in the garment in a regular or irregular pattern. These effects can also be produced in the specific area of the garment as per specific design. The washing is basically to give a used look to the garment by removing the dye on it chemically with help of stones, enzymes, bleaches, and water. These processes include the water involvement hence called the garment wet process.

A Typical 5-pocket jeans has at least 30 operations before it is finished and during sewing operations, a lot of stains and dirt can become part of garments. by the garment washing, these stains and dirt marks are also removed. By performing garment wet processing, the shrinkage of garments also takes place during this process. Therefore, no further shrinkage of garments takes place, once the customer has purchased the garment.

Garment wet processing is the final process in denim production and is significantly important because it is directly related to the aesthetic, quality, and value of finished garments, especially in denim. There are different washing techniques that produce different results. 
      • Rinse wash
      • Stone Wash
      • Enzyme wash
      • Bleach wash
      • Bag/Tie Wash
      • Softener

Rinse Wash

In rinse wash, the garments are also rinsed with the help of water without using chemicals. The garments can have been desized before the rinse wash. In the rinse wash process, the garments are just dipped in water, and then they are passed through hydro (extracts extra water) and later into the dryer. The rinse wash don’t give a special look to garment but removes starch and gives a mild raw look to the garment

Stone Wash

In the stone wash process, the garments are abraded with the help of stones. This wash enhances the grainline of the garment with mechanical abrasion. The stones are used with garments with ratio of 1 : 1.5 (75 kg stones for 50 kg load size). The grainline of garments is enhanced by the rubbing of garments with the help of stone. The stone type used are polymeric stones called pumice stones

pumice stone

Pumice Stone used in stone wash (Picture)

stone wash

Garments are offloaded after a stonewash (Picture)

After the stonewash procedure, the garments are loaded into the machine where these stones are removed from finished garments. This process is called derocking.

Effects of Stone Washing Time 

  • Stones may cause wear and tear of the fabric and may damage the washing machine from abrasion of the stone with fabric or machinery parts.
  • It may also create the problem of environmental disposition of waste of the grit produced by the stones.
  • Increase the labour cost required to remove stone dust from finished garments. Denim garments are required to be washed several times for complete removal of the stones.
  • The stone washing process may cause back staining and redeposition. 
  • The process is nonselective.
  • Metal buttons and rivets in the garments, as well as the drum of the washing machine some-times, get abraded which substantially reduces the quality of the garment and the life of the equipment. [R.Paul]


Enzyme Wash

The enzymes are the living organisms that get activated at a specific temperature. The enzyme wash is used for enhancing the grainline of garments with the usage of enzymes. They eat the dye bonds and remove dyes to give an abrasion effect. They enhance less grain line than the stonewash and also keep the soft hand feel and look of garments.
Temperature is the most important factor in enzyme treatment. Generally speaking, enzyme reaction increases with temperature but it is only activated within a temperature range in which the enzyme structure remains stable and unchanged. Beyond this opti- mum range, the enzyme activity decreases sharply as the protein structure of enzyme is tangled through thermal agitation.

In enzyme washing, cellulase enzymes are used. Hydrolysis of the cellulose, which is catalysed by cellulase, causes the surface fibres to become weakened and later they get removed when there is either fabric-to-fabric abrasion or fabric-to-stone abrasion during washing.

Advantages

Cellulase is economical and environmentally friendly as compared with stone washing using pumice stones. The percentage of fabric damages is reduced with cellulase treatment. The enzymatic treatment of denim fabric ensures the same result but consumes less water and time, resulting in less waste and damage to machines. The pollution, quality variability and imperfections are also reduced in enzymatic treatment. [R.Paul]

  • Enzymes can be recycled. 
  • The productivity of washing is increased due to the space formerly taken up by the pumice stones; the same washing machines can handle more jeans.
  • The time consumption for removing stone fragments from the denim garments is eliminated in the case of cellulase treatment.
  • The duration or number of rinse washing after enzyme treatment is less than pumice stone washing.
  • A small quantity of enzyme can replace several kilograms of pumice stones during washing, which ultimately leads to less damage to garments and machines.
  • Washed garments with a softer feel and better appearance is achieved in cellulase treatment.


Bleach Wash

The bleach wash is use to fade the color of the garments by using the chemical called bleach. Bleach removes the dye on the garments and gives a lighter shade to the garment. Most commonly used bleaching agents for garment wet processing are NaOCl, CaOOCl, and KMnO4. After the bleaching procedure, the garment has to be 'Neutralized' afterwards, to avoid the harmful effects of bleaching. During this neutralization, a chemicals named Sodium Meta Bi Sulphate is usually used. The bleach wash can be used on random areas to produce a random fading effect called random bleach wash

Softener

The softener is used after washing to give a soft and smooth look. It can be used alone to achieve a raw soft look. The softener binds with the garments and improves its hand-feel and drape and reduce the stiffness of the fabric. The softener also reduces abrasion and can be used to increase the strength and GSM of the fabric.

Process Flow

The process flow of garment processing varies as per the requirements of garment appearance. The garment dry processing and garment wet processing are bot carried in combination with one another to create the desired results. Considering the high volume of garment processing factories. These processes has to be exactly planned to avoid bottlenecks and ensure a smooth process flow. An example of a stone was process flow a jeans is shown below. 


Stonewash Flow

Example of Garment Processing with Stone Wash for a Jeans 

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