The color fastness test simulates the fastness of the color of the textile under different environments or conditions.There are many kinds of color fastness test items, such as soap washing, water stains, sweat stains, light resistance and so on. Different test items have certain differences in sampling.Even if it is the same test method, the sampling techniques of different personnel are affected by habits, subjective judgment and other factors, which will also lead to certain differences in the test results.

We have divided the color fastness items commonly checked into three categories: water bath type, pressure type and light type.

Water bath type

The water bath type represents color fastness to soap washing, color fastness to dry cleaning, etc. The test samples are stirred in the equipment and the sampling point is to get all the colors.

Pressure type

The pressure type represents the color fastness of water and sweat stains, etc. This type of sample shall be fully contacted with the lining under the specified pressure for testing. Sampling points: All colors shall be in contact with all types of lining, and the sampling requirement is higher than that of the water bath type.

Light type

Light type represents color fastness to light and color fastness to light and sweat. The size of such test sample depends on the instrument used, and the width is generally not less than 15mm. All colors shall be checked for sampling.

Taking the color fastness to washing as an example, the sampling points of color fastness are summarized below.

The first thing to consider when sampling for color fastness to washing is the lining fabric.Taking GB/T 3921-2008 as an example, it is stipulated in this standard that the choice of laminated fabric can be multi-fiber laminated fabric or two single-fiber laminated fabric.The lining fabric includes:

(1) Multi-fiber pasted fabric with wool and vinegar fiber (used for 40℃ and 50℃ tests, in some cases can also be used for 60℃ tests, need to be specified in the test report).

(2) Wool and vinegar-free multi-fiber laminated fabrics (for some 60 ° C tests and for all 95 ° C tests).

(3) Single-stick lining fabrics include: cotton, wool, viscose fiber, polyamide (nylon), polyester (polyester), polyacrylonitrile (acrylic), hemp, silk, vinegar fiber.Usually most testing institutions will choose multi-fiber lining, and the assessment requirements of multi-fiber lining are generally higher than that of single fiber lining.

In the following example, we will analyze the sampling methods used in the color fastness test according to different types of samples using the multi-fiber lining fabric test.

1 solid color sample

Samples are cut randomly along the warp or weft direction of the front of the fabric according to the size requirements of the standard.However, it is required that the sample cut down must be from a uniformly dyed, wrinkle free sample, and the distance from the cloth edge should not be less than 15cm, in order to make the whole test surface produce uniform results during the test.It should be noted that the cutting direction of the test sample and the original sample should be the same as the warp or weft.

2 yarn-dyed samples

According to the specification of the sample size in the standard, it is required to include all the colors of the sample when sampling. If a sample cannot contain all the colors of the sample, the sampling amount can be determined according to the proportion of each color of the sample and the size of sample cycle.

3 Printed samples

This kind of product is characterized by rich colors.Printing samples include small printing, large printing, color stripe and so on.The basic principle of sampling is to get all the colors on the sample. When sampling, pay attention to retaining the parts around the sample with the same color as the original sample for grading.If a sample cannot contain all the colors, increase the number of samples or determine the sample size according to the proportion of the colors, and give priority to the darker parts of the test.The following is a detailed analysis of all kinds of samples.

① a single small circular printing

When sampling, try to ensure a complete printing sampling, because sometimes due to the influence of color paste prescription, printing process and fabric structure and other factors, the same pattern in the same fabric printing will also have a certain color difference.Sampling can be cut according to the printing situation, but it is necessary to keep the samples of the same color around the sample as the comparison sample for the grading after the test.

② no circulation irregular small printing all over the ground

The color of this kind of sample is more complex. Before sampling, we should carefully observe the sample and select the representative place with uniform dyeing to cut.Mainly in the dark, brilliant color parts, usually take a sample can not contain all the colors, to prepare several more test samples.The color of the original sample and the test sample must be consistent and free of color difference to facilitate grading comparison after the test.

③ no circulation of large printing

Among the samples sent for inspection by the customer, some samples have large margins and large prints.The color of each pattern of such samples is different. Usually, one sample cannot cover all the colors. In this case, the position with relatively dark color should be evaluated first and the sample should be cut.In addition, it is necessary to take into account the proportion of each color and a certain proportion of the dark and light phases to sample. It is not possible to cut only the dark position, because there may be dark and light displacement phenomenon in the test process.

④ There are large circulation printing

This type of sample is also usually colorful, but it has cycles.Just cut from one of the circular patterns.If the sample of one cycle cannot meet both the test sample and the original sample, two cycle samples are needed. However, it is necessary to compare the color of the samples of the two cycles before cutting, so as to prevent the color difference between the same design and color of the two cycles.If one sample cannot contain all the colors, the number of samples can be increased to ensure that the color of the sample can be measured evenly.

⑤ color stripe printing sample

Samples within the specified test size shall include all color strips.Because the test state of color fastness to soap washing is a rolling type test, sampling can be done in different directions as long as all colors are collected.If a sample cannot contain all the colors, increase the number of copies or determine the sample size according to the proportion of each color, and give priority to the relatively dark parts for testing.

4. Dark and light colored samples with gradual dyeing

This kind of sample color is generally from light to deep or from deep to light, the transition of natural color.There are usually two or more gradients.Sampling should be in the dark and light locations to look for uniform staining to sample.Pay attention to avoid the position of the middle color gradient, because the color in this position is usually uneven, unrepresentative, easy to affect the test results.

Embroidery and flower samples

Embroidery, applique and car flower samples are all combined together by connecting wire and bottom cloth, which are uneven, but the soap-washing test is a dynamic test and does not affect the test results.Sampling should include all the flower, embroidery and background color parts, and pay attention to the sample after cutting to ensure that the applique, flower, small parts in the test process can not fall off.

Yarn and loose fiber

When the sample is yarn or loose fiber, the laboratory can weave the yarn into a fabric and sample it in the same way as the fabric.If the yarn or loose fiber cannot be made into fabric, the yarn or loose fiber should be taken to be approximately equal to half of the total mass of the laminated fabric, and the yarn can be wound into a sand bundle, and the yarn or loose fiber should be approximately equal to half of the total mass of the laminated fabric, and the yarn or loose fiber should be sutured with the laminated fabric for test.

7. Samples of ribbons and labels

There are more than the lining fabric and less than the lining fabric two.When sampling, the sample contains all the colors on the entire webbing. If the sample size is larger than the size of the taped fabric, the sample should be trimmed to match the size of the taped fabric.If the sample size is smaller than the lining fabric, several samples need to be stitched together so that the sample size matches the size of the lining fabric.

Matters needing attention

(1) The test sample for color fastness to washing must be on the front of the fabric or garment.

(2) The size of the sample should be sampled according to the size specified in the standard. If it is not satisfied, the sample can be spliced.

(3) In multi-color sampling, it is necessary to keep the same color parts around the sample as the original sample for grading comparison after the test.

(4) If the sample is easy to fall off during the test, attention should be paid to avoid it during the sampling to prevent the sample from falling off during the test.

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