How many types of color fastness test are there for fabrics?

Colour fastness concept and its type analysis

Colour fastness is the ability of printed textiles to resist damage from the environment during use or processing. It shows how firm the dyes and fibres are. It also tests the chromophore’s stability to environmental factors. Colour fastness is a key measure of printed and dyed textiles. It is a major quality concern for consumers.

Coloured textiles can discolour due to environmental factors. Dyes (pigments) may detach from the fibres. The dye molecules may destroy or alter. This affects the colour’s intensity, hue, and brightness. The discoloration is mainly due to sun, rain, friction, sweat, washing, and ironing. Also, steam can cause it. So, colour fastness is usually measured by various indicators. These are: light, weather, friction, sweat, washing, heat, steam, pool water, seawater, and brushing. Colour fastness to water, swimming pool water, and seawater. Also, to brushing, dry cleaning, organic solvents, and reduction. The current product standards specify colour fastness tests.

They depend on the type of textiles and the use of dyes and processing technology.

Light fastness and weather fastness to discolouration rating is the degree of discolouration before and after exposure to sunlight (colour difference) and at the same time exposed to sunlight 8 blue wool standard degree of discolouration (colour difference) compared to the aforementioned lighting, observation conditions, the degree of discolouration of the specimen is equivalent to the degree of discolouration of a certain level of the blue standard, the degree of colour fastness to light or climate that is the level of the blue standard that is, between the two grades will be assessed as an intermediate grade For example, 4~5, 6~7, etc.. The blue wool standard is made by dyeing wool fabrics with 8 kinds of blue dyestuffs of specified depth, representing 8 grades of colour fastness to light or weather.

Staining rating is the test of standard lining fabrics. It checks for stains using a grey (or color) sample card. The card uses a masked, round hole. We must test the lining fabrics against two pairs of round holes in small paper. You must conduct the test in the same lighting and conditions as the rating.

The visual rating must match the test.

When the test of the lining fabrics finds a color difference, the evaluator uses the grey or color card. If the color difference matches a level on the grey or color card, it tests the textiles’ color fastness. The color fastness level is the level indicated by the grey or color card.

If the test shows a colour difference in the lining fabrics of the sample card, we can set an intermediate level. For example, 2 ~ 3 or 4 ~ 5. The colour fastness to staining ranges from level 1, the most serious, to level 5, the lightest. It is also divided into 5 levels of 9 grades. The above visual rating method is subjective due to each person’s knot color. So, there are inevitable errors. Thus, people have tried to use an instrument rating instead of visual rating.

At present, there is an international standard ISO/TC38/SCIN965 ‘textile colour fastness test method – with the instrument on the lining of the fabric staining degree rating’. Our country also in reference to the adoption of the basis, promulgated the name and the ISO standard GB6410-1986 national standards. It is the use of spectral photometer or colourimeter on the dyeing fastness test and textile samples in contact with the lining fabrics and untreated lining fabrics for the colour measurement, and CIELAB for the single calculation of the colour difference between the two, or with the staining ratings calculation method A formula (6-14) will be converted into staining fastness rating value (SSR).

Colour fastness to light and weather test methods, test requirements and ratings

Colour fastness to light is a textile’s ability to resist sunlight or its simulation. There are three standard tests for colour fastness to light. They are: the daylight method, the xenon arc lamp tester, and the carbon fox lamp tester. The daylight method is the closest to the actual. But, its test cycle is long and inconvenient. It is hard to adapt to modern production management. So, the latter two methods are better. They save time and are easy to operate. The latter two methods use artificial light close to daylight. But, there are differences in the light spectra. So, the test results will change. When there is a dispute, the daylight method should still prevail.

The light fastness test is as follows. Arrange a specimen and 8 pieces of a blue wool standard together. Cover them with an opaque cover, like a black-and-white card, in a prescribed ratio. Expose them to the sun, without rain or other conditions, until the test specimen’s color fades. The fade must match a certain level of discolouration on a grey card or the blue standard. After exposure, remove the cover. Then, place the specimen and blue standard in the dark for 4 hours. Finally, assess the textile’s light fastness under a specified light source and conditions.

Climatic colour fastness is a printed textile’s resistance to weather and artificial conditions. It measures how well its colour holds up.

The standard tests for colour fastness to weather are:

The outdoor exposure method.

The xenon arc lamp tester method.

The climate colour fastness test is to expose a specimen to the open air. There should be no protection and specific conditions. Alternatively, test it in a xenon arc lamp tester for the same duration as a spray tan. In the same place, someone must cover a blue wool standard with glass to prevent rain or spray. The test ends when the specimen or blue wool standard discolors to a certain level on a grey card. Finally, check the specimen against the grey card for colour fastness to the climate. Someone can terminate it. Finally, we can assess it for weather fastness. The original sample and a test for discolouration form the basis of this. The test uses the blue wool standard and the same exposure time. For the outdoor exposure method, the climate changes a lot. Researchers should test the sample in different seasons. Then, take the average of the results.

Many factors affect the colour fastness of textiles to light and weather. They include the nature of the dyestuff, especially its photochemical stability. Other factors are the type of textile, its structure, and its colour shade. The wavelength of the light, air humidity, and hazardous gas content also matter. The colour fastness to rubbing test method is the same as that for the rubbing test.

Colour fastness to rubbing test method and staining rating

Colour fastness to rubbing is how firm a printed textile’s colour is against rubbing. The colour fastness to rubbing of coloured materials depends on two main factors. They are the amount of floating colours and the combination of dyes and fibres. The more floating colors on a textile’s surface, the worse its color fastness to rubbing.

The test method of colour fastness to friction is on the friction colour fastness tester. Use a standard white cotton cloth. You must desize, bleach, and ensure it is free of finishing agents. Fix a round friction head to the tester. Then, apply a 9N vertical pressure on the surface of the printed textile. Friction it back and forth, in a straight line for 100mm, at 60 times per minute. This will determine the degree of staining of the standard white cotton cloth. The test method depends on if the standard white cotton cloth is dry or wet. They divide it into dry and wet rubbing methods. The standard white cotton cloth should be wet in the distilled water in the diffusion. The test machine should then roll away excess water or evenly drip water onto the cloth. The water content should be 100% ± 5%.

The test procedure is as follows.

First, clamp a textile specimen flat in the test machine on the test bench. Then, fix dry or wet standard white cotton on the friction head. The standard white cotton’s warp and weft yarns must intersect the specimen’s at 45°. Next, the friction head must run along a 10 cm track on the test specimen. It must do this for 10, 1-second, straight-line, reciprocating tests. The specimen must be at least 20 cm x 5 cm, with the long direction of the warp yarn or the weft yarn. The test was for colour fastness to friction. It rubbed the fabric in the warp and weft directions. You must brush off any coloured fibres left on a standard white cotton cloth. It tested the staining of a grey (or colour) card against the stained white cotton cloth and the warp and weft.

Colour fastness to perspiration test method and rating method

Colour fastness to perspiration measures how well printed and dyed textiles resist sweat. Researchers mostly use it to test summer-coloured garments that often touch human skin.

The colour fastness to perspiration test is as follows. A fabric specimen (40mm x 100mm) sandwiches between two lining fabric pieces (each 40mm x 100mm). Sew along the short sides to form a combination of specimens. For printed fabrics, use the front sides of the lining pieces, with half of the contact cut off. The backs should be cross-covered, then sew the two short sides. If you can not include all the colours, need to use more than one combination of specimens). Then, researchers placed the two combined specimens in a simulation of the human body. This was to remove excessive sweat on the specimens. An acidic, alkaline sweat impregnation treated them. Then, the sweat colour fastness tester spring clamp held them.

A heavy hammer made the specimen pressure 12.5kPa. Then, the instrument moved to an insulation box at 37℃ ± 2℃ for 4 hours. Finally, remove the specimen’s combination. Then, use the grey (or color) sample card. It will assess the specimen’s discoloration and the fabric’s staining. In CB/T3922-1995 standard, there is a non-arbitrary rapid test method. The researchers saturated the method with simulated sweat.

Combine specimens one by one, flat on the plywood. Scrape off excess sweat, cover the plywood, and stack it.

Then, put a good spring platen and the hammer’s weight on it. This will apply 12.5 kPa of pressure to the specimens. Next, tighten the head screws to remove the hammer block’s weight. Finally, process at 70 ℃ for 60 min. the acid and alkali tests of the sweat in the specimen. Also, the discolouration and staining of each type of lining fabric. Choose the most serious one! They selected the most serious one.

In the above test, the researchers used two lining fabrics for each specimen. The artisans made the first from the same fibre as the specimen. The manufacturer made the second from the specified fibre. If someone blends or interweaves the specimen, they make a first piece from strong fibres. They made the second piece of low-content fibres. Also, human sweat is alkaline when first excreted. It becomes acidic after bacterial action. So, the pH value of the artificial sweat should match that of human sweat. Researchers add L-histidine to the artificial sweat. Human sweat has amino acids that affect the specimen’s discoloration.

Colour fastness to washing test method and colour change, staining rating

Colour fastness to washing measures how well textiles resist fading when washed. It tests printed and dyed fabrics. It is a key quality measure for most of these textiles.

The colour fastness to washing test is as follows. The specimen is a fabric, 40mm x 100mm. The two pieces of lining fabric are also 40mm x 100mm. Sew them together and put them in the colour fastness to washing tester. According to the selected method, add the test solution at a 50:1 ratio. Then, wash and dry the specimen. Use mechanical mixing under the test conditions. Finally, assess the colour fastness to washing with a grey or colour sample card. A grey (or colour) sample card tests for colour change and stains on the lining fabric.

The main device of the colour fastness to washing tester is a rotating shaft. It supports several glass or stainless steel containers. Each has a capacity of about 550mL ± 50mL (diameter 75mm ± 5mm, height 125mm ± 10mm). The shaft rotates at 40 times per minute ± 2 times. Its temperature control device can keep the test liquid at ± 2 ℃ of the target temperature.

China’s CB/T3921.1-1997 and GB/T3921.5-1997 specify a ‘colour fastness to washing test method.’ It lists five methods. The test solution formula and conditions differ. Use the method specified in the various product standards. We use Method 1 or Method 2 for general garments.

After washing, take out and wash with cold water twice. Then, rinse in cold water for 10 minutes. Squeeze out the water and combine with the specimen. Unfold and hang to dry in air at no more than 60°C. Then, use the grey sample card to check for discolouration and staining.

Ironing and steam pleat colour fastness test method and rating method

Ironing fastness is the degree of firmness of the colour of printed textiles to ironing. The colour fastness to ironing test is usually done on an ironing colour fastness tester. The main device for heating is a pressure device. It has a pair of smooth, parallel plates. Asbestos, wool flannel, and dry, undyed cotton cover the lower plate. It has an electric heater with accurate temperature control. It can apply a pressure of (4 ± 1) kPa to the specimen. The colour fastness to ironing test has three methods: dry, damp, and wet. They are for different types of fibre products, based on their end use.

Dry test is to put the dry specimen, front up, on the cotton liner. Then, put the heating device on the plate at the specified temperature for 15 seconds.

The tide test is to put a dry specimen face up on a cotton liner. Then, take a piece of cotton, the same size as the specimen’s lining fabrics. It must be an undyed, bleached white cotton with a smooth surface and a weight of 100-130 g/m². Immerse it in distilled water to saturate it. Then, place the wet lining fabric over the sample. Close the heating device’s upper plate. Apply pressure at the specified temperature for 15 seconds.

The wet test is to immerse the sample and the cotton lining fabric in distilled water to saturate them.

Then, place the wet specimen on the wet lining fabric. Lower the heating device’s upper plate. Apply pressure at the specified temperature for 15 seconds. After both tests, the cotton fabric (non-dyed, bleached, smooth 100-130 g/m²) must withstand a 15-second immersion under pressure.

After the above test, use a grey (or colour) sample card. This checks the specimen’s discolouration and the lining fabrics’ colour. Finally, test with quasi-atmospheric adjustments after 4h. Base the ironing test temperature on the fibre heat resistance and the textile. If necessary, you can also select other degrees. For blended or interwoven fabrics, use the lowest heat-resistant fibres’ temperature.

Using a household iron for the tests is difficult. It cannot meet the temperature and pressure requirements. This limits the test’s accuracy and reproducibility.

The colour fastness to vapour tucking is how well printed and dyed textiles resist it. The test method is to put the specimens on the gripper. Then, put the gripper and specimens into the steam box or pressure cooker with a jacket. This must meet one of the steam conditions in each group. Steam after taking out the combination of samples, folding line to expand, dry. Then, at (20 ± 2) ℃ and RH (65 ± 2) %, use wet 4 and a grey (or colour) sample card. Assess the specimen’s discolouration and the lining fabrics’ colour level.

Colour fastness to saliva test method and rating method

Colour fastness to saliva applies only to products for infants and children aged 2 and below. This includes children’s fluffy toys and garments. Infants and young children can absorb dyestuffs through their saliva and sweat. This may harm their health. So, it’s a key part of the eco-textiles’ colour fastness requirements. There are no such requirements for ordinary or decorative textiles in direct or non-direct contact. Baby products must have level 4 saliva color fastness. This is per the Oeko-Tex Standard 100 and China’s GB/T18885-2002.

For testing, take a 10cm x 4cm piece of fabric. Sandwich it between two single-fibre lining fabrics. Or, attach it to a multi-fibre lining fabric. Then, sew along a short edge to form a sample. In the test of printed fabrics, the front and two lining pieces must contact half of each. Cut off the remaining half. Then, cross over the back and sew the two short edges. Alternatively, use a piece of multifibre lining, sewing a short edge. If the test cannot include all the colours, use more than one combination of specimens. When testing yarn or loose fibres, take half the weight of the interlining fabric. Sandwich it between two pieces of single-fibre interlining fabric. Or, sandwich it between a 10cm x 4cm piece of multi-fibre interlining and a same-size, undyed piece.

Sew the four edges to hold it. The interlining fabrics used are each 10cm x 4cm. If you use a single-fibre interlining, the first piece must match the type of fibre in the specimen. The specified fibre must make the second piece. If the sample is for blended or interwoven fabrics, the fibres make up the first piece of the sample. The secondary content of fibres makes up the second piece. Lining fabric specs must follow CB7564-1987 to CB7568-1987 and CB11404-1989.

Put a piece of combined specimen into a 50:1 artificial saliva bath.

It must be completely wet. Then, place it at room temperature for 30 minutes. If needed, press and stir it slightly to ensure uniform penetration. Remove the test. Pour away the residual liquid. Use two glass rods to squeeze off the specimens on the excess test liquid. Use another specimen plate to scrape away the excess test liquid. We will sandwich the specimens between the two specimen plates. Then make the specimen subject to 12.5kPa. Then, put the instrument with the specimens in the thermostat. It should be at 37 ℃ ± 2 ℃ for 4 hours. After that, take it out. Remove all but a short side of the stitches from the specimens. Unfold them and hang them to dry in air over 60 ℃.

Finally, test the specimen discoloration per GB250-1995 and GB251-1995. Use a grey sample card. Also, test the lining fabrics and the specimens that contacted the side of the staining.

 

For more information on textile testing methods/standards
or textile testing machines, contact us:
What’s App: +86 180 2511 4082
Tel: +86 769 2329 4842
Fax: +86 769 2329 4860
Email: [email protected]