What is Textile Wet Processing?
Textile wet processing is a series of chemical and mechanical treatments that are applied to textiles during the manufacturing process, involved with the aqueous stage of pretreatment, dyeing, printing, and finishing. Textile wet processing constitutes innumerable steps leading to finished product, each having a number of complex variables and every lot is like a new lot and much depends on the well-trained operators rather than modern machines and technology. Wet processing technology is one of the major streams in textile engineering refers to textile chemical processing engineering and applied science. In this article I will discuss process flow chart and stages of textile wet processing for both woven and knit fabrics.
A general flow chart of textile wet processing as follows.
Flow Chart of Textile Wet Processing
Grey fabric inspection
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Sewing or stitching
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Brushing
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Cropping
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Desizing
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Scouring
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Bleaching
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Mercerizing
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Dyeing
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Printing
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Finishing
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Final inspection
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Delivery
Above each step of textile wet processing is described below.
1. Grey fabric inspection:
After manufacturing of grey fabric on loom, it is inspected using an inspection table. During this inspection, defects such as knots, broken and loose warp ends, broken weft ends are removed. In case of holes, either it is mended or the fabric is cut off depending on the position of the hole and its severity.
2. Batching:
Batching is a preparatory stage of dyeing. In this section grey fabric is received and sending of grey fabric to the dyeing section which will dye. It involves preparing a batch for dyeing according to machine capacity (so that equal amounts of fabric is passed through each nozzle of a dyeing machine), order and priority basis. Patching process in textiles helps improve efficiency, consistency, and quality control in the manufacturing process. It also helps to manage production on a larger scale and ensures that specific treatments or operations are applied uniformly to groups of similar textiles.
Batching of fabric for dyeing is done according to the following criteria:
- Order sheet (received from the buyer)
- Dyeing shade
- Machine available
- Type of fabrics (100% cotton, polyester cotton, chief value cotton, etc.)
- Emergency
The grey fabric is sent to the dyeing floor with a batch card providing details of the fabric rolls, the processes to be carried out and the sales contract against which the process is taking place. Records are maintained for the same. The criteria for proper batching are:
- To use maximum capacity of existing dyeing machines.
- To minimize the washing time or preparation time and machine stoppage time.
- To keep the number of batches as less as possible for same shade.
- To use a particular machine for dyeing same shade.
3. Stitching:
Stitching is done of different fabrics of the same variety undergoing same process to increase the length of the fabric, making it suitable for processing. It is done by plain sewing machine.
4. Brushing:
Brushing is done to remove the dirt, dust, loose fiber and loose ends of the warp and weft threads. If brushing is not done, the impurities obstruct the absorption of chemicals in next processes.
5. Shearing/cropping:
The shearing or cropping is the process by which the attached loose ends of the warp and weft thread is removed by cutting by the knives or blades. After this, the fabrics undergo singeing process.
6. Singeing:
In singeing process, the protruding and/or projecting fibers are removed from the fabrics by burning and/or heating to increase the smoothness of the fabric. If required, both sides of the fabric are singed. This process is optional.
7. Desizing:
Desizing is the process in which the sizing materials are removed from the fabric. This must be done before other wet processes of bleaching, mercerizing, dyeing, printing or finishing are carried out.
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8. Scouring:
The fibers from desizing may still contain grease, lubricants, antistatic agents, waxes, etc. The process by which the natural impurities (oil, wax, fat, etc.) and added/ external/adventitious impurities (dirt, dust, etc.) are removed from the fabric is called scouring. It is done by strong alkali like caustic soda (sodium hydroxide).
9. Souring:
Souring is the process in which the alkali is removed from the scoured fabric by using dilute acid solution.
10. Bleaching:
Cotton has some natural coloring matter, which confers a yellowish-brownn color to the fiber. Bleaching is the process by which the natural colors (nitrogenous substance) are removed from the fabric to make the fabric pure and white. It is done by bleaching agents such as hydrogen peroxide or sodium hypochlorite. Although there are different bleaching agents that can be used for bleaching cotton, using hydrogen peroxide (H2O2) is most common. In addition to an increase in whiteness, bleaching results in an increase in absorbency, levelness of pretreatment and complete removal of seed husks and trash.
11. Mercerizing:
Mercerizing is the process by which the cellulosic materials are treated with highly concentrated sodium hydroxide (NaOH) to impart properties such as strength, absorbency capacity and luster. Mercerizing swells the fabric, imparting increasing dye affinity, tensile strength, and luster to the fabric. This process is optional.
12. Dyeing:
Dyeing is the process of coloring fibers, yarns or fabrics with either natural or synthetic dyes. Dyeing imparts beauty to the textile by applying various colors and their shades onto a fabric. Dyeing can be done at any stage of the manufacturing of textile such as fiber, yarn, fabric or a finished textile product including garments and apparels. The property of color fastness depends on two factors, selection of proper dye according to the textile material to be dyed and selection of the method for dyeing.
Color is applied to the fabric by different methods and at different stages of the textile manufacturing process.
- In stock dyeing, the fiber is dyed even before it is spun.
- Top dyeing is the process of dyeing the slivers, that is, the fiber is dyed at the stage just before the appearance of finished yarn. This process is more popular in combed wool and in the production of melange yarns.
- Yarn dyeing may be done in hank form or in package form. The package dyeing may be done for yarn cheeses or yarn beams.
- Space dyeing consists of dyeing the yarn at intervals along its length.
- Piece dyeing consists of dyeing fabrics in small batches according to the demands for a given color.
- In solution pigmenting or dope dyeing, the dye is added to the solution before it is extruded through the spinnerets for making synthetic filaments.
- In garment dyeing, the dye is applied to finished products such as apparels and garments.
13. Printing:
Printing is the process for producing a pattern on yarns, warp, fabric or carpet by any of a large number of printing methods. The color or other treating materials, usually in the form of a paste, are deposited onto the fabric which is then usually treated with steam, heat or chemicals for fixation.
14. Finishing:
There are numbers of finishing treatments to give special effects. The finishing treatments are carried out according to buyer requirements, which are followed by folding, packaging and delivery.
Conclusion:
Wet processing is a very important process of fabric. Textile wet processing requires careful control of chemical formulations, temperature, and processing times to achieve the desired results while minimizing environmental impact. The key to success in textile wet processing technology will be the indication of highly trained manpower at lucrative wages in structured manner.
References:
- Handbook of Value Addition Processes for Fabrics By B. Purushothama
- Textile Processing and Properties: Preparation, Dyeing, Finishing and Performance by Tyrone L. Vigo
- Basic Principles of Textile Coloration By Arthur D Broadbent
- Kiron, Mazharul Islam (2011) Process Sequence of Textile Wet Processing Technology, https://textilelearner.net/flow-chart-of-textile-wet-processing/
Editor of Fashion2Apparel. She is a fashion designer and ex-lecturer in Fashion Designing. She wants to spread fashion knowledge throughout the world.
