What is textile sample dyeing in the dyeing lab? Based on the colour requirement and…
Accuracy and stability of fabric dyeing play a vital role in fabric dyeing business, in this article we will the factors affecting the fabric dyeing accuracy and stability, with these in mind, fabric dyeing sample could be approved by customer fast and accurate.
Table of Contents
Things to check before sampling
For new orders requiring dyeing sampling, here is a quick checking list:
- Standard sample is complete
- The light source should be defined
- Fabric specifications should be confirmed
- The color fastness requirement(washing fastness, rubbing fastness, light fastness, and etc.)
- The requirements of finishing process( softness, penetration resistance, anti-bacteria, fire resistance, UV protection and etc.)
- The lead time for the final dyeing samples
Any doubts in this stage should be confirmed with the customer.
Common problems relating to the standard sample from customer are:
- The organization specifications of the original sample are different from the organization specifications specified in the colorrequirementlist. In this case, due to the difference in light absorption, reflection and light transmission of the fabric, it is difficult for the sample to match the original color. At this time, you should make a few more samples with different shades and different shades for customers to choose, so as to increase the customer’s recognition rate.
- The original sample is not fabric, but printed cardboard. In this case, due to the smooth surface of the paper sample, strong gloss, and the paper sample is printed paint, rather than dyes, etc., under the specified light source, the color of the dyed sample is generally difficult to match the original sample. At this time, only a few more samples with different shades and shades can be printed for customers to choose.
- When dyeing cotton-polyamide or cotton-polyester blended fabric, if the original sample provided by the customer, the color depth and color uniformity of the bicomponent fiber are poor, and there are two-color phenomenon; at this time, there are usually two situations: the first is to keep This kind of two-color effect; secondly, don’t want two-color effect, but even one color. Therefore, the shade of bicomponent fiber should be leveled (in the original sample, the shade of bicomponent fiber is different due to poor dyeing uniformity). In this case, be sure to ask the customer clearly, so as not to get confirmation of the sample.
- The original sample has a certain amount of fluorescence under the light source. In this case, pay special attention. Generally, there are two possibilities: first, the fabric should have a fluorescent effect under a specific light source; the second fabric itself is not required to have fluorescence, but when dyeing, in order to brighten, it is helpless to add a fluorescent whitening agent. At this time, you must first clarify the true requirements of the customer, and then make the approved samples according to the requirements.
- The original sample is silk fabric or acrylic fabric (or acrylic fleece), but the small sample needs to be made of pure cotton, or cotton-polyester or cotton-polyamide. In this case, the original sample is often dyed with acid dyes or cationic dyes. The vividness is so good that the sample cannot meet the brightness requirements of the original sample. In this case, you must print a similar sample for the customer’s reference and explain the reason to the customer. If fluorescent brightener is added to increase the brightness, the customer’s consent must be obtained.
- The color number of “white” is often included in the customer’s color requirement list. Such as: natural white, ivory white and pearl white, etc., but there is no physical standard. In this case, it is necessary to figure out in advance the so-called “shade” in the color requirement list, whether it refers to natural white, bleaching or whitening. If the customer is confused about this and it is difficult to determine, the three samples of natural white, bleaching and whitening must be printed first and recognized by the customer. If the whitening sample is identified, three samples of yellow light, red light and blue light are usually provided. , Let the customer confirm. In this case, we must take it seriously, otherwise, it will be easy to have color and light differences with customers during the inspection and acceptance of large goods, or even rework.
- For cotton-nylon, cotton-polyester, nylon-polyester, polyester-viscose and other interwoven or blended fabrics, the original sample provided by the customer is sometimes a flash sample (that is, the two fiber components have different colors and have a flashing effect); It is necessary to determine exactly which fiber is which color, and generally cannot be changed. If the color is reversed, there will generally be two situations: first, the overall effect of the fabric surface is not consistent; second, if the blending ratio is equivalent and the weaving specifications are appropriate The overall effect of the cloth is basically similar, giving people an illusion, but it leaves a potential problem, that is, once the customer finds the wrong color of the fiber, they will refuse to receive the goods and must be dyed again. Therefore, you should be very careful about the shining color samples and not careless.
- The nylon and polyester contained in cotton-nylon or cotton-polyester fabrics are not all matte yarns. Sometimes there are shiny yarns, nylon and polyester luster strengths, which have a great impact on the brightness and brilliance of the dyeing color of the fabric. Big. Therefore, it is necessary to determine whether the nylon or polyester contained in the original sample provided by the customer is shiny or matte. If it is shiny, the same fabric must be used for proofing. If the matte yarn is used for proofing, the color will be sure Is inconsistent. If fluorescent whitening agent is used for brightening, it is usually not accepted by customers, so the customer’s approval must be obtained in advance.
- The nylon component in cotton-nylon interwoven fabric is usually nylon 6, but nylon 66 is also available. As the amino content of nylon 6 is more than twice that of nylon 66, nylon 6 has a high affinity for anionic dyes, has good dye depth, and is easy to dye deep and dense colors. However, nylon 66 is only suitable for dyeing medium and light colors due to its low amino content.
Therefore, before proofing, first try to ask the weaving factory about the type of nylon, and second, try to dye deep and thick colors with nylon 6 blanks. If nylon 66 is used for dyeing deep and dense color, even if it is saturated with acid bath and ultra-high temperature (100℃), it is often difficult to meet the depth requirements. Even if the small sample reaches the depth, the reproducibility of the large sample is often very poor, and there are also problems of low color fastness and serious sewage.
- Twill fabrics with front and back sides generally use the twill side as the front side, and sometimes there are exceptions, with the back side as the front side. Therefore, we must carefully review the original sample provided by the customer. If you find that the swatch in the color requirement listis facing up, you must figure out whether the reverse is the front facing color, or the customer puts the swatch on the reverse side. Don’t be empirical and change without authorization, otherwise reprinting the sample is a trivial matter, and it will be a big mistake if it is put into production.
- Sometimes the color requirement listprovided by the customer includes both the original sample (usually different from the required texture in the color requirement list) and the approved sample (usually the first approved sample issued by other factories, and the texture is generally the same as the color requirement list. The requirements are the same), but there is usually a certain shade or shade difference between the two.
At this time, there are generally two customer requirements: one is based on the original sample as the standard, and the approved sample is re-printed; the other is based on the first approved sample provided as the standard and re-proofed. In this regard, it is important to understand the customer’s intentions and not subjectively. The proofing color requirement list provided by the customer generally has clear light source requirements, such as natural light, fluorescent light, D65 light, TL84 light, CWF light, F/A light, UV light, etc.
Things to confirm with production planning dept before sampling
Before making samples, the quality of the semi-finished products should be determined uniformly with the production planning department, such as mercerized or unmercerized cloth, sanded or unsanded cloth, white cloth or bleached cloth, pre-shaped cloth or post-shaped cloth, and pre-shrunk cloth or not The principle of shrinking cloth, etc. is: the cloth used for proofing must be consistent with the cloth used for mass production in the future to unify the process flow and process conditions, and it should not be changed on the way after confirmation.
Before making samples, first confirm the production method with the production planning department, such as whether the mass production is liquid jet dyeing or flat cylinder jig dyeing. Once confirmed, it should not be changed on the way. Because the proofing conditions of liquid flow dyeing and jig dyeing are different, the dyes and auxiliaries used are also different; if it is changed, it can only be re-proofed, and the sampling prescription must not be used in combination.
Selecting the right dyes: The general principle
According to the customer’s color details for dyeing depth, shade and color fastness requirements, carefully select dyes. For example: for deep and thick colors, use high-strength, high-deepness, and high wet fastness dyes; for light and light colors, use high-level dyeing and high light fastness dyes; for chlorine bleaching Chlorine-resistant dyes should be used if the degree of resistance is required; dyes that are resistant to organic solvents should be selected for dry-cleaning fastness; when dyeing cotton-polyamide or cotton-polyester interwoven fabrics, especially when dyeing flash white or flashing colors Use dyes with low mutual contamination. If it is nylon/cotton or cotton/nylon stretch fabric, when dyeing nylon, disperse dyes and neutral dyes or acid dyes should be matched to ensure brightness, color fastness and uniformity of the fabric surface to meet customer requirements. What I want to point out here is that nylon and spandex have a great difference in the color absorption (shade, shade) of disperse dyes. Dyeing nylon with disperse dyes alone has good level dyeing properties, but it often produces spandex on the cloth surface. “Silk” jumps out, affecting the uniformity and color of the cloth.
Other risks in real production: Selecting the professional color matching cabinet
- There are many brands of standard light boxes and lamps used, and light boxes and lamps of different brands have certain differences in the color light;
- Paste prescription paper and color samples on the gray inner wall of the light box, which will have a certain impact on the color and light. Therefore, when the standard light box is color matching, the color and light in the factory light box match, but in the light box of the client company There is a color deviation in the color, which makes it difficult to recognize the small and large color samples.
Therefore, the standard light box, especially the lamp tube, must use products that meet international standards, and the lamp tube must be used correctly to eliminate the non-standard light box caused by the non-standard light source of the lamp tube and the improper use of the light box, resulting in color differences.
D65 light source
D65 light source is artificial daylight light source. Compared with natural light sources, their responses to colored light are not completely the same. Some customers confuse the two and think that D65 light is natural light. Therefore, the color requirement list for proofing is often specified as D65 color matching, and when accepting small samples (or large samples), natural light is used for color matching. Therefore, there are often differences between the factory and the customer. In this regard, we must communicate with customers to unify their understanding and eliminate misunderstandings.
Challenges from Different light sources
Some customers require two different light sources for color matching, and even require two light sources to be turned on at the same time, and a mixed light source for color matching. In this case, there is usually an obvious problem of light jumping, that is, under different light sources, different colored lights are produced, or even completely unrecognizable.
Different dyes have different structures, and have different light absorption and reflectivity for different light sources. It is not easy to solve the problem of color matching dyes (2~3 dyeing). The only way is to do dye compatibility test. , Choose dyes that are compatible with the light source. Under different light sources, the degree of light jumping is relatively small.
Validating the requirement, following the right steps and selecting the reliable tools, should help you win the approval from the customer accurate and fast.