Silk is extracted from the cocoons and becomes the raw material for weaving silk. One silkworm cocoon can draw out about 1,000 meters of cocoon silk, and several cocoon silks are combined into raw silk.
After processing, raw silk is divided into warp threads and weft threads, and they are interwoven to form a silk fabric according to a certain organizational law, which is the weaving process. The production process of all kinds of silk fabrics is different, and can be roughly divided into two types: raw weaving and cooked weaving.
Raw weaving means that the warp and weft silk is first made into fabric without dyeing, which is called green silk, and then the green silk is dyed into finished products. This kind of production method has low cost and short process, which is the main method used in silk weaving production at present.
Cooked weaving means that the warp and weft yarns are dyed before weaving, and the finished silk does not need to be dyed to become a finished product. This method is mostly used in the production of high-grade silk fabrics, such as brocade and taffeta.
Before weaving, preparations must be made, such as dipping to soften sericin, doubling and twisting to improve product performance, as well as warping and weft rolling. At the same time, because silk is highly hygroscopic, it is necessary to do a good job of preventing moisture. At present, the automatic looms used in silk weaving production mainly include: water jet looms used to produce synthetic fiber filament fabrics and rapier looms used to produce multi-color weft jacquard fabrics.
Dyeing and finishing
The printing process has an important position in the production process of silk. Because only by using dyeing and finishing technology, we can perfectly reproduce our favorite colors and patterns on the white blanks, so that the fabrics are more artistic. The process mainly includes four processes of refining, dyeing, printing and finishing raw silk and fabrics.
The silk consists of two monofilaments, the main body of which is silk protein, and the outer layer is wrapped with sericin. Most of the pigments, oils, waxes and inorganic salts are present in sericin. These impurities have a great influence on the effect of printing and dyeing, so they must be removed before dyeing. In long-term practice, people have mastered the characteristics of sericin that is easy to dissolve in hot water under the action of chemical agents or enzymes, and take advantage of the weakness of sericin to put raw silk or raw silk into soap (or synthetic detergent) and The mixed solution of soda ash (sodium carbonate) is heated, and the sericin is heated and then hydrolyzed. After such refining, the sericin is removed and the silk protein is preserved, and impurities such as pigments, fats, and waxes are removed, so as to obtain silk products with a white color. The raw silk after degumming is called cooked silk. The degree of raw silk degumming must be determined according to production requirements.
After the white silk is refined, it enters the dyeing stage. Dyeing is the process of chemically reacting dyes with silkworms and silk, so that the silk can be dyed with various colors. Since silk is a protein fiber, it is not alkali-resistant, so dyeing should be carried out in an acidic or close to neutral dyeing solution. At present, the main dyes used in silk fabrics are: acid dyes, reactive dyes, direct dyes and vat dyes. The color dyed with acid dyes is brighter. After dyeing, it is treated with cationic fixing agent to improve the washing fastness of the product. Reactive dyes have good washing fastness on silk.
The dyeing method of the fabric varies with the type of fabric. For example, crepe and gauze fabrics are dyed with rope or overflow jet dyeing, and spinning, silk, and satin fabrics are dyed with open width hanging or roll dyeing.
After all, a color is monotonous. In addition to dyeing, people also use printing techniques to make silk colorful. Printing refers to a process in which dyes are printed on fabrics in accordance with the designed colors. Commonly used printing processes include direct printing, discharge printing, and anti-dyeing. Direct printing means that the color paste is directly printed on the silk fabric through the screen printing plate. It is one of the basic printing methods and can be printed with a variety of dyes. Discharge printing, also known as engraving printing, is a process of discharge dyeing using engraving agent. Before printing and dyeing, the silk is dyed with acid dyes and reactive dyes with azo structure, and then printed on the colored silk according to the pattern. The engraving (discharge) paste made from the engraving agent that destroys the pigment, after steaming, the ground color of the engraving paste becomes white, which is called "carving white".
Anti-dye printing is to print silk fabrics with "anti-white" paste or "color-resistant" paste according to patterns, and then dye them after they are dried. Because the pattern part has the anti-dyeing agent in the "anti-white" paste or the "color-proof" paste, it will not be dyed, while the rest are all colored.
After the silk fabric is refined, dyed, and printed, the final finishing work can be carried out on the fabric. The finishing process mainly solves the problems of dampness, wrinkles, and uneven width left over from the previous processes, highlights the softness of the silk fabric itself and increases its wearing function, and mainly adopts two methods of mechanical finishing and chemical finishing.
Mechanical finishing includes tentering finishing, steam ironing, calendering, etc.; chemical finishing is mainly to add chemical agents, such as softeners, antistatic agents, fire retardants, sand lotions composed of soda ash and trisodium phosphate, etc. So as to achieve the effect of anti-wrinkle, anti-shrinkage, softness and thickness. The treated fabrics are not only more suitable for wearing, but the consumption field of silk is also broadened. After the printed silk is made, you can start to make exquisite handicrafts and noble and gorgeous clothing with oriental charm.