Denim Garment Finishing Treatments: Stages, Types and Process

Denim Finishing Process:
A characteristic of denim garments (jeans) is their used-look appearance. After the production of the denim garment, a wide range of procedures is applied to widen the coloristic potential of a product, which mainly is available in blue or black color. In denim manufacturing, it is an amazing fact that one style of jeans is converted into different colors, which is achieved by garment washing. In today’s denim manufacturing, many denim finishing are done to give the jeans a broken-in look, much like what unwashed (dry denim) denim looks like after it has been worn many times. Denim finishing includes chemical shrink resistance, Sanforizing, liquid ammonia treatments and permanent press processes. The finishing and Sanforizing of denim usually takes the form of a continuous (inline) method, but depending on the plant and machinery, this may be carried out in several stages. Denim finishing gives the fabric a softer feel, enhance its appeal without any strength loss and improve wear life, color retention and fashionable flair. There are two main types of denim finishing treatments one is chemical and another is mechanical processes which are done for achieving diverse distressed or abraded looks and any number of distinctive designs to fit consumer’s requests. Different types of denim finishing treatment giving fabrics the final touch to create the right high-quality fashion style.

Stages of Denim Finishing:
The different mechanical and chemical treatments in denim garments in combination intend to remove the dye from the surface without intensive damage of the yarn structure. Denim finishing involves several key stages that enhance the fabric’s look, feel, and performance. The finishing process is made up of the following stages:

1. Brushing (on one or both sides)
2. Singeing (on one or both sides)
3. Desizing (where necessary)
4. Padding (one or two padding mangles)
5. Stretching to the desired cloth width (where necessary), Stretch Meter (compensator)
6. Weft skew correction (antitwister) 6–16% excluding 3/1 and 2/1 twill, to prevent twisting of the fabric
7. Drying (12–24 cylinders) to a residual moisture content of 15–20%
8. Stentering (clip or clamp stenter)
9. Sanforizing (moistening, shrinking, calendering) with a shrinkage of 11–15% to a residual shrinkage value of 2–2.5%

These stages can vary depending on the desired characteristics and end use of the denim fabric.

Chemical Finishing of Denim Garments:
Various chemical finishes such as bleaching, enzyme washing and acid washing are the major types of chemical finishing used for denim.

Bleaching:
The bleaching is performed to discolor the denim in specific locations. The degree of bleaching action depends on the strength of the bleach, temperature and duration of the treatment.

Enzyme washing:
The environmental friendly finishing process ‘enzyme washing’ is used to create prominent effects at seams, pockets and hems.

The advantages of the enzyme process are:

• Improved abrasion, colour removal without damaging the fabric strength
• Simple and easy treatment
• Environmentally friendly
• Greater variety of effects are achievable
• Shorter washing times.

Acid washing:
Acid washing is also a popular method for denim garment finishing. It is also known as stone washing, which is accomplished with pumice stones. Due to severe abrasive action, surface fiber damage occurs. In some instances the pumice is impregnated with potassium permanganate (an oxidative bleaching agent), this chemical being less damaging to the cotton fiber than sodium or calcium hypochlorite. With the use of pumice stones, intensive abrasion of the garment can be achieved in big drum washers. The garment is washed with 0.5–3 times the weight pumice stones. Substantial removal of indigo dye into the wash liquor can lead to back staining which names a blue staining of the undyed weft and re-deposition of indigo on the garment. Substantial losses of abrasive material lead to significant release of sand into the waste water. The abrasive washing conditions also lead to rapid damage of the drum of the washer. Often the pumice stones are also soaked in chemical solutions prior to their use to intensify the color reduction by additional oxidative attack.

Following this bleaching and stone washing, the garments are washed with sodium bisulphite (reducing agent) to complete the removal of the brown color generated by the permanganate wash. This treatment has the effect of surface bleaching the indigo as well as giving the garments a softer handle and creating a distressed look.

Wrinkle finishing:
Resin is applied on the finished garment, in which wrinkles have to be created manually or semiautomatically. A wrinkling effect on denim creates unique vintage looks that make garments more fashionable, hence adding value to denim garments and improving their saleability in market. It prevents the intermolecular slippage in the fiber core, and it may not be harmful if formaldehyde-free resin is used. Resin decreases the tensile and tear strength, abrasion resistance. It gives an unpleasant odour as well as an unwanted harsh, stiff feel. It may turn the fabric yellow after chlorine bleaching, and sometimes it is difficult to remove the unfixed resin

Mechanical Finishing of Denim Garments:
Mechanical denim finishing includes the process of stone washing and micro-sanding.

Stone washing:
Mechanical stone washing is similar to the chemical washing process of the acid wash. Here also stones are tumbled with freshly dyed denim, but it does not require any chemicals. The final look of the product depends on the size, shape and hardness of the stones used. In several instances the metal buttons and rivets get damaged due to the mechanical action.

Micro-sanding:
There are three types of micro-sanding: sandblasting, machine sanding and hand sanding. The sand blasting process is the most common, which is accomplished by passing a very abrasive substance through a nozzle at the denim at high speed and pressure that creates many different patterns in the denim. Machine sanding is performed by using a machine (similar to the machine used to sand down wood furniture), whereas hand sanding is done with a fine-grain sandpaper by hand.

Abrasive processes:
Abrasive treatments intend to imitate the use of the jeans; examples are sanding, brushing and sandblasting. Sandblasting has been banned with regard to health hazards due to aspiration and inhalation of silica dust, thus leading to severe silicosis. Dry ice (solid CO₂) has been proposed as an alternative, which does not form finely dispersed dust particles.

The most recent development in the processing of denim has been the use of laser technology to imitate the human hand. VAV Technology GmbH produces the X-Burner system, a dry method of producing patterned effects on denim. This system allows a wide range of effects to be produced efficiently with minimum damage to the fabric. The VAV Technology for automated denim processing increases productivity, uniformity and quality of the finished product.

Conclusion:
Denim garment finishing treatments are specialized processes applied to enhance the appearance, texture, and durability of finished denim garments like jeans, jackets, or shirts. Denim finishing treatments play a crucial role in transforming raw denim into versatile, stylish, and comfortable garments. With advancements in technology, sustainable methods like enzyme washing, ozone treatment, and laser etching have emerged, reducing environmental impact while maintaining aesthetic appeal.

References:

Jahanara Rony

Editor of Fashion2Apparel. She is a fashion designer and ex-lecturer in Fashion Designing. She wants to spread fashion knowledge throughout the world.

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