The Fascinating Journey of a Piece of Fabric: Exploring Textile Printing and Dyeing Processes
Textile printing and dyeing is a massive system engineering that involves multiple processes such as raw materials, semi-finished products, weaving, printing, dyeing, and finishing. Among them, spinning, weaving, and printing and dyeing are three relatively independent industries.
In the printing and dyeing industry, the process is not a fixed pattern but varies depending on different raw materials, yarn types, fabric structures, and printing and dyeing requirements. For example, there are significant differences between chemical fiber textile printing and dyeing, wool textile printing and dyeing, and silk reeling, weaving, dyeing, and finishing, to the extent that they cannot be easily borrowed from each other. So, let's first understand the conventional processes in these three industries, namely spinning, weaving, and printing and dyeing, to have a basic understanding of the spinning and dyeing industry and the overall impression of the source of bed fabrics.
Main processes in spinning: cotton cleaning, carding, combing, drafting, coarse yarn spinning, fine yarn spinning
Main processes in weaving: warping, sizing, beaming, threading, weaving, finishing
These are the main processes, and each company may have slight differences in the process depending on their products and needs. Below, I will share with you the conventional cotton textile printing and dyeing process as an example.
Cotton textile printing and dyeing process:
Fabric preparation - Stitching - Singeing - Cold calendering - Scouring and bleaching - Mercerizing - Pre-stretching - Sizing - Printing (flat screen or rotary screen printing) - Steaming - Soaping - Finishing and setting - Pre-shrinking - Calendering - Quality inspection and packaging
Usually, after the fabric enters the printing and dyeing factory, it needs to go through processes such as inspection, spreading, batching, fabric preparation (joining two fabric pieces with the same face), and stitching before undergoing singeing.
Singeing: The singeing process seems magical. You will see the fabric swiftly passing through high-temperature flames, sliding over the intense flames without burning.
This is because the fabric is tightly woven, and it heats up slowly. By the time it reaches the ignition point, it has already moved away from the flame or the red-hot metal surface, achieving the purpose of singeing off the fuzz without damaging the fabric.
Reason: If the fabric is not singed, it will have excessive and uneven fuzz on the surface, poor smoothness, and it will be prone to staining and shedding during subsequent dyeing and finishing processes, leading to defects in printing and dyeing.
* Singeing aims to remove the fuzz on the fabric surface, making it smooth and beautiful, and preventing uneven dyeing and printing due to the presence of fuzz. It improves the fabric's luster and cleanliness.
* It improves the fabric's resistance to pilling, particularly for synthetic fabrics.
* It enhances the fabric's style and makes it more crisp.
Cold calendering is a process that follows singeing. The fabric needs to be cooled for more than twenty hours.
2. Desizing, Boiling, and Bleaching
Desizing, boiling, and bleaching are processes involved in textile production.
*Desizing: Before boiling, the sizing material on the fabric needs to be removed. This process is called desizing.
To enhance the abrasion resistance, smoothness, and antistatic properties of the warp yarn during weaving, sizing processing is carried out before weaving. The sizing material on the fabric affects the fabric's water absorption properties and also impacts the quality of dyeing and finishing products. Moreover, it increases the consumption of dyeing chemicals. Therefore, the sizing material needs to be removed before boiling, and this process is called desizing. It involves removing the sizing material from the fabric.
*Boiling: Boiling, also known as refining, aims to remove fiber impurities (both natural and artificial impurities) and improve the fabric's processing performance, especially its wetting properties.
During the growth of cotton fibers, natural impurities such as pectin substances, waxy substances, and nitrogenous substances are present. After desizing, most of the sizing material and some natural impurities have been removed from the cotton fabric. However, a small amount of sizing material and the majority of natural impurities still remain on the fabric. The presence of these impurities makes the cotton fabric appear yellowish and reduces its permeability. Additionally, the presence of cottonseed hulls significantly affects the appearance quality of cotton fabric.
Therefore, the fabric needs to be boiled in a concentrated alkaline solution at high temperature for a relatively long time to remove the remaining impurities.
*Bleaching: After boiling, the cotton fabric still retains natural pigments on the fibers, which results in an insufficiently white appearance. This can affect the brightness of colors during dyeing or printing.
The purpose of bleaching is to remove pigments and primarily improve the whiteness of the
Mercerization refers to the use of concentrated alkali solution to treat cotton woven fabrics, giving them a silk-like luster on the surface. More importantly, it improves the dimensional stability of the fabric, meaning that the cotton fabric becomes more stable in size.
This processing technique is called Mercerization or Mercerizing in English.
Significance of Mercerization:
* Improved dimensional stability and reduced shrinkage rate.
* Changes in mechanical and tensile properties, such as decreased breaking strength.
* Improved adsorption properties.
* Enhanced appearance with a silk-like luster.
4. Width Control (Sizing)
Width control, also known as sizing, involves adjusting the tension of the warp and weft yarns of the fabric to achieve consistent fabric width and density. This process increases the dimensional stability of the fabric.
5. Starch Sizing and Shaping
Different types of jacquard fabrics undergo starch sizing to some extent before calendering. Sizing allows the starch to adhere to the fiber surface, preventing the fabric from shrinking excessively. Sizing also has a softening effect and promotes friction between fibers.
Currently, there are two widely used methods for printing: rotary screen printing and flat screen printing. Due to their low tension, they are less prone to deformation and can achieve vibrant and fully saturated colors. Both methods result in fewer fabric defects and are particularly suitable for producing multiple varieties. Rotary screen printing and flat screen printing both require a screen, which originates from block printing techniques using paper, metal, or chemically etched patterns.
Rotary screen printing uses nickel rotary screens, while flat screen printing involves stretching the screen onto a metal or wooden rectangular frame. Flat screen printing can be done manually (hand table printing) or mechanically (flat screen printing). Due to the different printing methods, there is a certain allowable range for the dimensions, with flat screen sizes ranging from 305mm to 1200mm. Generally, the circumference of a rotary screen is 640mm, 820mm, or 1018mm, which determines the multiple cycles of the pattern.
The characteristic of rotary screen printing is that the pattern is continuous without repeat seams.
The screen for flat screen printing is square-shaped, allowing for unlimited pattern repeats. Flat screen printing has repeat seams.
Overall, rotary screen printing has the highest production output, typically around 3500 yards per hour, with the speed depending on the complexity of the pattern. Flat screen printing offers superior precision and pattern size compared to rotary screen printing, but it is less efficient in terms of production speed. The choice between rotary screen and flat screen printing depends on various factors such as fabric usage, pattern size, and material considerations.
7. Steaming and Soap Washing
Steaming: After printing textiles, except for ice dye and soluble reactive dyes, most dyes require steaming.
Purpose: Steaming is done to facilitate the absorption of moisture and raise the temperature of the printed textile, accelerating the reduction and dissolution of dyes on the fibers. This allows the dyes to penetrate into the fibers and fix onto them, resulting in colorfastness. The steaming process varies depending on the properties of the dyes and fibers.
Soap Washing: It is a necessary and important process that follows steaming. During soap washing, the detergent interacts with the dyes through physical and chemical actions. The dispersing, suspending, and chelating properties of the detergent prevent the dyes from re-staining the fabric. The aim is to improve wash fastness and prevent color bleeding.
8. Pre-shrinking Treatment
During the printing and dyeing process, fabrics undergo mechanical tension that creates internal stress. When the fabric becomes wet, the internal stress relaxes, resulting in shrinkage. Therefore, it is necessary to perform mechanical pre-shrinking treatment on the fabric in actual production to reduce the shrinkage rate of cotton fabrics. This ensures the stability of the finished product's dimensions, maintains the fabric's neat width, and increases the added value of the product.
9. Calendering Treatment
Also known as glazing.
It is a process in fabric finishing. By utilizing the physical plasticity of fibers under high pressure or temperature conditions, the fabric surface is flattened or patterned through calendering to enhance its luster. Similar to ironing, this method flattens and smoothens the surface of the fabric, giving it a special sheen, increasing its brightness, and improving its drape and smoothness.
10. Quality Inspection and Packaging
At this stage, the printing and dyeing of the fabric is considered complete. The fabric is inspected, rolled, and undergoes quality control. If there are any pattern flaws, manual correction is carried out before packaging for shipment.
The journey of a piece of fabric from cotton bolls to its final form involves a multitude of processes, labor, technology, creativity, and scientific knowledge. Each stage plays a crucial role in creating fabrics of superior quality, durability, and aesthetic appeal. Understanding the intricate processes behind textile printing and dyeing allows us to appreciate the craftsmanship and dedication involved in producing the fabrics we use in our daily lives.