How does the “gray damage” defect of sand-washed silk fabrics occur? How to prevent and repair it?
Answer: After the silk is sand washed, a soft layer of frosty white fluff (commonly known as grayscale) will be produced on the surface of the fabric. In silk sand washing finishing, it is divided into light, medium and heavy sand washing. Light sand washing requires the silk surface to be basically gray-free, maintain the original appearance, and have a soft and smooth hand feel. Heavy sand washing requires that the silk surface is not completely shiny, has a large gray scale, has a strong velvet feel, and has good wrinkle resilience; the indicators of medium sand washing are between light and heavy sand washing. During the coloring and sand washing process of silk, it is very easy to produce “gray damage” defects. Because of the different states and physical and chemical effects during finishing, the “gray damage” produced is also different. If the silk is not arranged in time during the sand washing process, the silk will be tangled or the amount of silk and water will be improperly controlled, resulting in “strips of dust” (commonly known as white strips); when using a centrifugal dehydrator to dehydrate, the brakes will be too fast, causing the dehydrator to “Gray bruises” (commonly known as abrasions) caused by being out of sync with the silk; “grey bruises” caused by the blockage of the silk pieces when the vat is being dyed and the silk being wrapped upside down on the oval guide rollers due to tension during the rope machine dyeing. “(commonly known as strains); various “local bruises” caused by friction between pieces of silk and equipment and friction between pieces of silk during the finishing process. There are also cases where the sanding process is too heavy or has been repaired many times, or the coloring or rope-like coloring temperature is too high and the time is too long, which makes the silk surface gray too much, as if it was heavily sanded, that is, “uniform gray damage” is formed. .
The prevention methods are as follows.
① During sand washing, control the amount of cloth and water; strictly control the silk processing time (including the time for soda ash sand washing of white blanks and the time for hot air and cold air).
② Do not brake suddenly when dehydrated.
③ When coloring, attention should be paid to controlling the amount of silk for different equipment and different silk blanks. The liquor ratio should not be too small to avoid excessive squeezing and friction of the blank silk and causing gray damage; the liquor ratio for rope-like coloring To operate it properly, the silk must be able to move freely in the dyeing bath without getting tangled; the water flow speed of the dyeing tank must match the speed of the silk to prevent clogging; for silk that does not require grayscale, use a rope When the coloring machine is coloring, the temperature should not be too high, otherwise it will easily cause friction between the silk blanks due to boiling and cause dust damage.
There are five methods of repair.
④Sand washing method. The principle of sand washing is used to produce uniform fluff on the silk surface to cover up “local gray damage”.
②Light oil wiping method. Dip a piece of silk of the same color into a small amount of olive oil and rub it in your hands to allow the olive oil to fully penetrate. Use this silk to rub the whitened gray wound in one direction to make a small amount stick to the villi of the gray wound. Olive oil, the color becomes slightly darker, and it looks like there is no gray damage. When operating, be careful not to use too much oil, otherwise oil spots will appear. This method can only temporarily remove the dust damage. After cleaning, the dust damage will reappear.
③Dye solution application method. Use a brush to dip the coloring liquid into the stain, and apply it carefully to the gray wound so that the color of the gray wound is the same as elsewhere. Then use an iron to flatten it to fix the color at high temperature.
④Enzyme treatment method. Utilizing the principle of enzyme refining, that is, protease can decompose proteins at appropriate temperatures and pH values, and the silk that needs to be repaired is treated with enzymes. The fine fluff that causes “uniform gray damage” on the silk surface is broken down first, thereby removing the gray. However, the action of 2709 alkaline protease is slower, and due to the long wet treatment time, the color of the silk will fall off and the hue will change. You can use the “Silk Wash 2000” fast protease produced in Switzerland, which can remove grayscale in a short time and has good results.
⑤Singeing method. The principle of singeing is used to burn off the uniformly damaged fluff formed on the silk surface to remove the gray. However, this method is difficult to master. High-temperature singeing can easily cause the silk to deteriorate and turn yellow, so special attention must be paid.
The above ①②③ method is suitable for repairing “localized gray damage” such as “white strips” and “scratches”, and ④⑤ method is suitable for repairing “uniform gray damage”.
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