What is the colour fastness of the washing test?
The colour fastness to washing test simulates the degree of colour fastness of textiles to different detergents and washing environments. There are various methods of laboratory colour fastness to washing test, and different test methods may have certain differences in temperature, washing solution and drying procedures. In larger testing institutes, the colour fastness test adopts a process-type working method with sub-posts, which is usually divided into sampling post, testing post and grading post. So even if the same test method, different inspectors in the sampling technique by habit, subjective judgement and other factors will lead to a certain difference in test results. This article discusses sampling methods of different types of fabrics in the washing colour fastness test.
Sampling methods for colour fastness to washing tests
The sampling of colour fastness to washing should first take into account the lining fabric. Taking GB/T 3921-2008 as an example, this standard stipulates that the choice of lining fabric can be either multi-fibre lining fabric or two single-fibre lining fabrics. The multi-fibre lining fabric includes:
(1) Multi-fibre lining fabrics containing wool and vinyl fibres (for tests at 40°C and 50°C, and in some cases also at 60°C, which need to be specified in the test report).
(2) Multifibre interlining fabrics without wool and acetic fibres (for some tests at 60°C and all tests at 95°C). Single-fibre lining fabrics include cotton, wool, viscose, polyamide (nylon), polyester (polyester), polyacrylonitrile (acrylic), ramie, silk, and vinyl. Usually, most testing institutes choose multi-fibre lining, and the requirements for multi-fibre lining are higher than those for single-fibre lining.
The following is a detailed analysis of the sampling methods for different types of samples in the colour fastness to washing test, taking the multifibre lining fabric test as an example.
The daily testing samples in the laboratory are roughly divided into plain samples, colour woven samples, printed samples, dark and light colour gradient dyeing samples, embroidery and turning samples, beading, drilling samples, yarn and loose fibres, openwork fabrics and so on. In GB/T 3921-2008, when the specimen is required to be fabricated, the specimen size is 40mm×100mm.
Plain colour samples
According to the requirements of the standard on the size of the specimen, along the front of the fabric in the direction of the warp or weft direction randomly cut specimens. However, it is required that the specimen must be taken from a large, evenly dyed, wrinkle-free sample that is representative of the batch dyeing. And the distance from the edge of the fabric must not be less than 10cm, so that the test can produce uniform results on the whole surface of the action.
Colour woven samples
According to the standard specimen size, it is required to take a sample that can contain all the colours of the sample. If one sample cannot contain all the colours of the sample, the sample size can be determined according to the proportion of each colour in the sample. Priority to the darker parts of the test or may increase the number of samples. However, the number of samples taken shall not exceed 3 sets.
These products are characterised by a wide range of colours. Printed samples include small prints, large prints, inter-colour stripes and so on. The basic principle of sampling, is the requirement to take the way of digging, take all the colours, and when digging, pay attention to retain the sample around the same colour parts as the original sample of the rating comparison. If a sample can not contain all the colours, you can increase the number of copies or according to the proportion of each colour to determine the amount of its sample, giving priority to the dark test. The following is a detailed analysis of the various types of samples.
1 Single cycle of small print
Single cycle of small print sampling to try to ensure that the sample in a complete print on the sample. Because sometimes, due to the influence of factors such as colour paste prescription, printing process and fabric structure, there will be a certain colour difference between the prints of the same type of pattern. Sampling should be taken in the way of digging for sampling. Digging should pay attention to retain the sample around the same colour as the test after the rating comparison of the original sample.
2 No cycle and irregular of small prints
This type of sample colour is relatively rich, before sampling, we must first carefully observe the sample, select the dyeing uniformly representative of the place for digging the sample. Usually take a sample can not contain all the colours, to increase the number of samples.
3 No cycle of large prints
In the samples sent by the customer for inspection, such as some bed sheets, quilt covers, etc., these samples are characterised by large margins and large prints. The colours of each pattern of these samples are different. Usually cutting a sample can not cover all the colours, in this case to give priority to the relatively darker colours in the position of digging specimens. And take into account the proportion of each colour depth between a certain proportion to take samples, not only digging the dark position. Because in the test process there may be a phenomenon of shallow and deep colour swimming shift, so the sampling should not only take into account the specimen of the staining situation, but also take into account the specimen of the colour change.
4 There is a cycle of large prints
This type of sample is usually also rich in colour, but it is cyclic. Simply scoop the sample on one of the looping patterns. If there are other colours that are not available, consider increasing the number of samples taken.
5 Intercolour stripe of print samples
Samples should be taken in the specified sample size to include all the interstripe colours. As the colour fastness to soap washing is a rolling test, unlike the colour fastness to perspiration is a static test, there is no prescribed pressure requirements, sampling can not be in accordance with the direction of the interstripe sampling, as long as all the colours can be taken. If a sample can not contain all the colours, you can increase the number of copies or according to the proportion of each colour to determine the amount of samples, priority to take the relatively dark parts of the test.
Dark and light colour gradient dyeing samples
These samples are generally coloured from light to dark or dark to light with a natural transition. Usually, there are two or more gradient colours. Sampling should be done by digging in the darker and lighter colours to find a uniformly stained area. Be careful to avoid the middle of the colour gradient position, because this position of the colour is usually uneven, not representative, and easy to affect the test results.
Embroidery and appliqué samples
Embroidered, appliquéd and embroidered samples are all unevenly bonded to the backing fabric by connecting threads. However, the soap washing resistance test is a dynamic test, unlike the colour fastness to perspiration test, which has a certain pressure requirement that does not affect the test results. Sampling should include all the parts of the pattern, embroidery and base colour. And we should pay attention to ensure that the appliqué, embroidery and small parts can not fall off in the test process after cutting the sample.
Samples of beads, hot diamonds
Consumers often encounter some troublesome problems in daily use, such as ironing diamonds coming off after washing, or the colour of beads staining other parts of the clothes, and so on. Therefore, some enterprise standards will also require the assessment of these parts of the discolouration and whether to fall off and so on. Therefore, the sampling can be done according to the customer’s requirements or according to the principle of strict assessment. Sampling should include all the beads and ironing parts, and should ensure that the beads and ironing parts will not fall off during the test.
Yarn and loose fibres
When the sample is yarn or loose fibres, the laboratory can weave the yarn into a fabric and sample it as if it were a fabric. Alternatively, when the sample is yarn or loose fibres, a mass of yarn or loose fibres approximately equal to half the total mass of the backing fabric is taken and sewn in a sand bundle to the backing fabric for testing.
There are two types of samples: larger than the lining fabric and smaller than the lining fabric. Samples are taken from the entire webbing. If the sample is larger than the size of the lining fabric, the sample is trimmed to fit the lining fabric. If the sample size is smaller than the backing fabric, several pieces of the sample are spliced to match the backing fabric.
Lace, hibiscus lace, openwork samples
These samples usually also have some printing, under the premise of meeting the sampling requirements of printed samples. Also note that when taking samples, try to cut the fabric structure of the dense parts, to prevent the specimen in the test process scattered.
Colour fastness to washing, also known as colour fastness to washing/colour fastness to soaping, is an assessment of the fabric in the soap washing process of the original fabric colour loss and lining staining.
The principle of the test is that the textile specimen and one or two pieces of standard lining fabric are sewn together, placed in soap or soap an anhydrous sodium carbonate mixture, in the specified time and temperature conditions, mechanical agitation, and then after washing and drying. The original sample is used as a reference sample, and a grey sample card or instrument is used to assess the discolouration of the sample and the staining of the backing fabric.
Colour fastness to water, also known as colour fastness to water stains, is to assess the colour loss of the original fabric and the colour staining of the lining of the textile after soaking in water.
The test principle is a textile specimen and a multi-fibre lining fabric or two pieces of single-fibre lining fabric combination together, immersed in water, squeezed out of the water, placed in the middle of the two flat panels of the test device, subjected to the prescribed pressure, to be a certain period of time, take out the test specimen and the lining fabrics drying, the original sample as a reference, the grey samples of the card or the instrument evaluation specimen discolouration and the lining of fabrics stained with the colour.
The WashTrue Washing Color Fastness Tester adopts a smart temperature control algorithm to ensure that the washing colour fastness test meets the test standards and the results are reliable. This machine is applicable to standards such as ISO 105 C06:2010, AATCC61-2013e3, GB/T 12490-2014, etc.
(1) The test specimen for colour fastness to washing must be taken from the front of the fabric or garment as the test surface.
(2) When the specimen is a piece of cloth, the specimen must be obtained from a large sample that is wrinkle-free and representative of the batch-dyed or printed-dyed material, not less than 10cm away from the edge of the cloth so as to produce uniform results on the whole surface of the test. The distance from the edge of the cloth shall not be less than 10cm in order to produce uniform results on the whole surface of the test.
(3) Samples shall be taken in all colours as far as possible. If a sample can not contain all the colours can be cut according to the proportion of each colour priority of the relatively dark position or take more than one group of samples, but generally no more than three groups of samples. It should be noted that the dark position of the sampling should be confirmed by at least three inspectors. Different types of samples have crossed and should meet the respective sampling principles.
(4) When samples are taken by a digging way, the operator needs to pay attention to retain the same colour around the digging specimen parts as the original sample after the test rating comparison.
(5) The samples that are easy to fall off in the test process should be avoided when taking samples to prevent the samples from falling off in the test process.
(6) When taking samples, pay attention to the size of the sample needs to match the size of the lining fabric, can not be larger or smaller than the size requirements of the lining fabric.