Colour Fastness Properties of Textiles
What is color fastness?
Color fastness is a term which is used in the dyeing of textile materials, We can define colorfastness as, having color that will not run or fade with washing or wear. There are many properties of textile fabrics, among them colorfastness property is most important. It is a property of a colorant which allows it to retain its different characteristics despite degradation conditions such as exposure to light and dry cleaning.
One of the major sources of consumer complaints relating to dyed fabric is their variable and nonacceptable fastness. Dyed fabrics behave differently when they are in contact with various conditions like rubbing, washing, perspiration, and exposure to light during the fabric/garment’s life. Fabric can be fast to one condition but can easily exhibit poor fastness in another condition. Therefore, it is necessary to test the fabric as per the required end use, and that test method needs to be mentioned clearly to avoid any complications. Typically, the class of dye, subtype of dye, color of dye, shade depth, and dyeing process impart significant effects on the final fastness rating of the fabric.
It is also very important to mention how the fastness rating is given. Typically, there are two ways to do this. One is the subjective assessment of the observer by using the standard gray scales under standard light conditions as shown in Figures-1 and Figure-2. The rating is given by assessing the difference on the gray scale rating and comparing it with the obtained similar difference on the tested and nontested fabric.
The final rating is given on the basis of the similar level of difference on the gray scale. However, different ratings can be given by different observers on the same tested fabric.
A second rating can be given by the use of an instrument called a spectrophotometer, which is based on ΔE as shown in Table-1. The rating is still given on the basis of the standard gray scale, which is fed into the computer system, but it is given by using ΔE and so human error and bias can easily be avoided.
Table-1: Gray Scale Rating of Spectrophotometer Based on ΔE
Different Types of Color Fastness of Fabrics:
There are various types of color fastness test for fabric. Important color fastness tests are given below:
Color fastness to rubbing:
This test exhibits the amount of color that is transferred from the dyed sample onto the white fabric under specific conditions of rubbing. It is performed by using crock meter equipment, which can be operated manually or motorized. There are two main types of test methods that are used to determine the effect of rubbing, one is BS EN ISO-105-X12, while the second is the AATCC crock meter method, test method 8. With the BS EN ISO-105-X12 test method, dyed fabric dimensions should not be less than 50 mm . 140 mm. However, with the AATCC-8 specimen, dimensions should be at least 50 mm . 130 mm.
The AATCC also developed another method, the rotary vertical crock meter AATCC-116, which is used for smaller samples as well as for printing fabrics. A dyed fabric sample is locked onto the base of the crock meter, while white bleached fabric, whose dimensions are 5 cm . 5 cm, is mounted onto the finger and rubbed against the dyed fabric. The finger is rubbed against the dyed fabric at the speed of one turn per second (10 . 10 s). Then the white finger cloth is removed and evaluated by using the gray scale shown in Figure-1.
A rating is given on a scale of 1–5. The procedure for wet rubbing fastness is exactly similar to that of the dry one, apart from the fact that the finger cloth is wet prior to rubbing. It is very important to keep the pick-up of the fabric at 65%, otherwise significant variations can be reported. This test method is equally good at determining the rubbing rating for a range of solely dyed fabrics as well as for after-treated dyed fabrics.
Color fastness to washing:
This method is used for assessing the resistance of the color of the dyed fabric to all kinds of wash in water with soap and detergent. There are numerous methods and submethods for assessing dyed fabric fastness to washing as washing conditions vary from country to country as well as from consumer to consumer. Therefore, various test methods have been developed. Two major ones that are adopted by many international organizations are discussed below. The first is the BS EN ISO 105-C06:2010, Textiles-Tests for Color Fastness (Part C06: Color Fastness to Domestic and Commercial Laundering). The second is the AATCC Test Method 61-2003, Colorfastness to Laundering, Home and Commercial: Accelerated. There are various methods to assess the color fastness to washing as per ISO methods ranging from C01 to C06. A different soap percentage, temperature, time of washing, and level of washing are used in methods from C01 to C06 as shown in Table-2.
Table-2: Conditions of Color Fastness for C01–C06
In BS EN ISO 105-C06:2010, dyed fabric having dimensions of at least 10 cm . 4 cm are sewn together with standard multi-fiber strip. There are two types of multi-fiber strip containing six types of fibers; type DW has wool, while type TV is without wool. Loose dyed fibers can also be assessed by compressing the samples through padding and then sewing it between the multi-fiber strip. To test, the colored yarns can be converted to knitted fabric, or the above mentioned approach for loose fibers can also be repeated for yarns as well. The sample is washed in a washing machine at a speed of 40 revolutions per minute using one of the sets of conditions. A washing solution is prepared by dissolving 4 g of detergent per liter of water. The reference detergent may be AATCC 1993, WOB (without optical brightener) or ECE (European Colorfastness Establishment) detergent with phosphates. Sixteen different subtests can be adopted as per requirement.
These test methods have a different liquor volume, washing temperature,chlorine level, perborate level, quantity of steel balls as well as pH.
Abrasive action on the dyed fabric is achieved by a low liquor level and by using a high number of steel balls. The gray scale rating for change of color and staining can be given by using the respective gray scales. A rating can be given on a scale of 1–5. The C06 method is equally effective for all type of dyes whether synthetic or natural. A similar washing machine is used as in ISO C06; however, the sample size and washing conditions are different. The sample size is 50 mm . 100 mm for Test No. 1A and 50 mm . 150 mm for Test Nos 2A, 3A, 4A, and 5A.
Color fastness to light:
This test is used to assess color fading when the sample is kept under a specific light source. The test samples are exposed to light for a certain time (24, 36, 48, 72 h, etc.) or to customer demand, under certain conditions of light source, temperature, and humidity, and compared with standard samples. A blue scale is used to determine the color change. This test is quite important for the dyestuff manufacturer, the dyeing units, and the retailer. Certain products like carpets, curtains, and upholstery require excellent light fastness due to their end use performance requirement.
The two most commonly used standard test methods are (1) BS EN ISO 105- B02:2014; Textiles, Tests for Color Fastness: Color Fastness to Artificial Light: Xenon Arc Fading Lamp Test and (2) AATCC Test Method 16. Typically a xenon arch-based light source exhibits similar spectral content to that of daylight and therefore is much preferred. In addition, an effective filter needs to be used between the lamp and specimen to control the intensive light. These variables can easily lead to significant changes in the light fastness rating. Therefore, it is important to mention which conditions have been used to expose the sample.
The tested samples as well as the standard blue wool reference are kept in a specific light source under the standard conditions. A certain portion of the samples is partially covered as per the standard and the remainder is exposed to the specific light source. A comparative subjective rating is given depending on the equal color change between exposed and nonexposed samples and standard specimens. A rating will be given on a scale of 1 (lowest) to 8 (highest). Half-a-scale rating such as 3–4 can also be given. The American and European scales use two different sets of reference standards. The European scale rating is given from 1 to 8, while for the American it is given from L2 to L9. It is important to note that these scales are not interchangeable and that the scale on which the rating is based should be mentioned.
Color fastness to perspiration:
This test is used to assess the change in color of the fabric when exposed to perspiration. Tested samples are dipped in a solution that mainly consists of histidine. The sample is then placed in the perspirometer equipment, where it is treated with histidine solution; a standard sample is separately dried. A gray scale can be used to determine the change in color and staining. Two significant test methods in this area are the AATCC Test Method 15 and the BS EN ISO 105-E04. Two major types of perspiration are based on the solution pH. In an alkaline solution, a pH of 8 is maintained by using NaOH; other ingredients are 0.5 g of histidine monohydrochloride monohydrate, 5 g of sodium chloride, and 2.5 g of disodium hydrogen orthophosphate per liter. For acidic pH, a pH of 5.5 is maintained; other ingredients of the recipe are kept the same as above.
The fabric is thoroughly wetted with the desired acidic or basic pH solution, having a liquor ratio of 50:1, by dipping the sample in the solution for half an hour at ambient temperature. To remove the extra liquor, the sample is wiped through two glass rods and then placed in between the two plates of the perspirometer under the recommended pressure of 12.5 kPa. The sample is dried in an oven at 37°C for 4 h. The rating is given as 1–5 by using the gray scale.
Color fastness to sublimation:
The color fastness of a dyed article is not only affected by washing, water, or rubbing but also by heat in many forms, such as by pressing, dry heat, or heat with moisture. Some dyes are sensitive to heat and hence can fade/bleed due to the effect of heat. This test is intended to assess resistance of color to the action of dry heat only and not by pressing. Mostly, there are two methods to evaluate color fastness to dry heat: ISO 105–P01, Color Fastness to Dry Heat (Excluding Pressing) and AATCC Test Method 117-2004-Color Fastness to Heat: Dry (Excluding Pressing). The methods are applicable to textiles of all kinds and can be conducted at different temperatures depending upon the stability of fibers, which can be influenced by chemicals used during dyeing, printing, chemical processing, and by physical factors involved in color change and staining. Nondyed fabric attached to tested samples are exposed to heat. The rating is given using the gray scale.
A specimen of the sample under test is treated with dry heat for 30 s under a specified temperature and pressure. Three temperature options are 150°C ± 2°C, 180°C ± 2°C, and 210°C ± 2°C, and it is important to mention the temperature at which the sample is exposed as it can significantly alter the results. A pressure of 4 ± 1 kPa is applied to the sample during testing. The treated specimens are conditioned and evaluated using the gray scale for color change and staining on adjacent fabric.
References:
Color fastness is a term which is used in the dyeing of textile materials, We can define colorfastness as, having color that will not run or fade with washing or wear. There are many properties of textile fabrics, among them colorfastness property is most important. It is a property of a colorant which allows it to retain its different characteristics despite degradation conditions such as exposure to light and dry cleaning.
One of the major sources of consumer complaints relating to dyed fabric is their variable and nonacceptable fastness. Dyed fabrics behave differently when they are in contact with various conditions like rubbing, washing, perspiration, and exposure to light during the fabric/garment’s life. Fabric can be fast to one condition but can easily exhibit poor fastness in another condition. Therefore, it is necessary to test the fabric as per the required end use, and that test method needs to be mentioned clearly to avoid any complications. Typically, the class of dye, subtype of dye, color of dye, shade depth, and dyeing process impart significant effects on the final fastness rating of the fabric.
It is also very important to mention how the fastness rating is given. Typically, there are two ways to do this. One is the subjective assessment of the observer by using the standard gray scales under standard light conditions as shown in Figures-1 and Figure-2. The rating is given by assessing the difference on the gray scale rating and comparing it with the obtained similar difference on the tested and nontested fabric.
 |
| Figure-1: Standard gray scale for staining |
 |
| Figure-2: Standard gray scale for coloring |
Table-1: Gray Scale Rating of Spectrophotometer Based on ΔE
ΔE
|
Gray Scale
| |
≥0
|
<0.4
|
5
|
≥0.4
|
<1.25
|
4–5
|
≥1.25
|
<2.10
|
4
|
≥2.10
|
<2.95
|
3–4
|
≥2.95
|
<4.10
|
3
|
≥4.10
|
<5.80
|
2–3
|
≥5.80
|
<8.20
|
2
|
≥8.20
|
<11.60
|
1–2
|
≥11.60
|
1
| |
Different Types of Color Fastness of Fabrics:
There are various types of color fastness test for fabric. Important color fastness tests are given below:
- Color fastness to rubbing
- Color fastness to washing
- Color fastness to light
- Color fastness to perspiration
- Color fastness to sublimation
- Color fastness to water
- Color fastness to sea water
- Color fastness to hot pressing
- Color fastness to chlorinated water
Color fastness to rubbing:
This test exhibits the amount of color that is transferred from the dyed sample onto the white fabric under specific conditions of rubbing. It is performed by using crock meter equipment, which can be operated manually or motorized. There are two main types of test methods that are used to determine the effect of rubbing, one is BS EN ISO-105-X12, while the second is the AATCC crock meter method, test method 8. With the BS EN ISO-105-X12 test method, dyed fabric dimensions should not be less than 50 mm . 140 mm. However, with the AATCC-8 specimen, dimensions should be at least 50 mm . 130 mm.
The AATCC also developed another method, the rotary vertical crock meter AATCC-116, which is used for smaller samples as well as for printing fabrics. A dyed fabric sample is locked onto the base of the crock meter, while white bleached fabric, whose dimensions are 5 cm . 5 cm, is mounted onto the finger and rubbed against the dyed fabric. The finger is rubbed against the dyed fabric at the speed of one turn per second (10 . 10 s). Then the white finger cloth is removed and evaluated by using the gray scale shown in Figure-1.
A rating is given on a scale of 1–5. The procedure for wet rubbing fastness is exactly similar to that of the dry one, apart from the fact that the finger cloth is wet prior to rubbing. It is very important to keep the pick-up of the fabric at 65%, otherwise significant variations can be reported. This test method is equally good at determining the rubbing rating for a range of solely dyed fabrics as well as for after-treated dyed fabrics.
Color fastness to washing:
This method is used for assessing the resistance of the color of the dyed fabric to all kinds of wash in water with soap and detergent. There are numerous methods and submethods for assessing dyed fabric fastness to washing as washing conditions vary from country to country as well as from consumer to consumer. Therefore, various test methods have been developed. Two major ones that are adopted by many international organizations are discussed below. The first is the BS EN ISO 105-C06:2010, Textiles-Tests for Color Fastness (Part C06: Color Fastness to Domestic and Commercial Laundering). The second is the AATCC Test Method 61-2003, Colorfastness to Laundering, Home and Commercial: Accelerated. There are various methods to assess the color fastness to washing as per ISO methods ranging from C01 to C06. A different soap percentage, temperature, time of washing, and level of washing are used in methods from C01 to C06 as shown in Table-2.
Table-2: Conditions of Color Fastness for C01–C06
Test
|
Liquor
|
Temperature (°C)
|
Time (min)
|
Reproduces Action of
|
C01
|
0.5% soap
|
40
|
30
|
Hand washing
|
C02
|
0.5% soap
|
50
|
45
|
Repeated hand washing
|
C03
|
0.5% soap
0.2% soda ash
|
60
|
30
|
Medium cellulosic wash
Severe wool wash
|
C04
|
0.5% soap
0.2% soda ash
|
95
|
30
|
Severe cellulosic wash
|
C05
|
0.5% soap
0.2% soda ash
|
95
|
240
|
Very severe cellulosic wash
|
C06
|
4 g/L reference
detergent + perborate
|
Various
|
Various
|
Domestic laundering
|
In BS EN ISO 105-C06:2010, dyed fabric having dimensions of at least 10 cm . 4 cm are sewn together with standard multi-fiber strip. There are two types of multi-fiber strip containing six types of fibers; type DW has wool, while type TV is without wool. Loose dyed fibers can also be assessed by compressing the samples through padding and then sewing it between the multi-fiber strip. To test, the colored yarns can be converted to knitted fabric, or the above mentioned approach for loose fibers can also be repeated for yarns as well. The sample is washed in a washing machine at a speed of 40 revolutions per minute using one of the sets of conditions. A washing solution is prepared by dissolving 4 g of detergent per liter of water. The reference detergent may be AATCC 1993, WOB (without optical brightener) or ECE (European Colorfastness Establishment) detergent with phosphates. Sixteen different subtests can be adopted as per requirement.
These test methods have a different liquor volume, washing temperature,chlorine level, perborate level, quantity of steel balls as well as pH.
Abrasive action on the dyed fabric is achieved by a low liquor level and by using a high number of steel balls. The gray scale rating for change of color and staining can be given by using the respective gray scales. A rating can be given on a scale of 1–5. The C06 method is equally effective for all type of dyes whether synthetic or natural. A similar washing machine is used as in ISO C06; however, the sample size and washing conditions are different. The sample size is 50 mm . 100 mm for Test No. 1A and 50 mm . 150 mm for Test Nos 2A, 3A, 4A, and 5A.
Color fastness to light:
This test is used to assess color fading when the sample is kept under a specific light source. The test samples are exposed to light for a certain time (24, 36, 48, 72 h, etc.) or to customer demand, under certain conditions of light source, temperature, and humidity, and compared with standard samples. A blue scale is used to determine the color change. This test is quite important for the dyestuff manufacturer, the dyeing units, and the retailer. Certain products like carpets, curtains, and upholstery require excellent light fastness due to their end use performance requirement.
The two most commonly used standard test methods are (1) BS EN ISO 105- B02:2014; Textiles, Tests for Color Fastness: Color Fastness to Artificial Light: Xenon Arc Fading Lamp Test and (2) AATCC Test Method 16. Typically a xenon arch-based light source exhibits similar spectral content to that of daylight and therefore is much preferred. In addition, an effective filter needs to be used between the lamp and specimen to control the intensive light. These variables can easily lead to significant changes in the light fastness rating. Therefore, it is important to mention which conditions have been used to expose the sample.
The tested samples as well as the standard blue wool reference are kept in a specific light source under the standard conditions. A certain portion of the samples is partially covered as per the standard and the remainder is exposed to the specific light source. A comparative subjective rating is given depending on the equal color change between exposed and nonexposed samples and standard specimens. A rating will be given on a scale of 1 (lowest) to 8 (highest). Half-a-scale rating such as 3–4 can also be given. The American and European scales use two different sets of reference standards. The European scale rating is given from 1 to 8, while for the American it is given from L2 to L9. It is important to note that these scales are not interchangeable and that the scale on which the rating is based should be mentioned.
Color fastness to perspiration:
This test is used to assess the change in color of the fabric when exposed to perspiration. Tested samples are dipped in a solution that mainly consists of histidine. The sample is then placed in the perspirometer equipment, where it is treated with histidine solution; a standard sample is separately dried. A gray scale can be used to determine the change in color and staining. Two significant test methods in this area are the AATCC Test Method 15 and the BS EN ISO 105-E04. Two major types of perspiration are based on the solution pH. In an alkaline solution, a pH of 8 is maintained by using NaOH; other ingredients are 0.5 g of histidine monohydrochloride monohydrate, 5 g of sodium chloride, and 2.5 g of disodium hydrogen orthophosphate per liter. For acidic pH, a pH of 5.5 is maintained; other ingredients of the recipe are kept the same as above.
The fabric is thoroughly wetted with the desired acidic or basic pH solution, having a liquor ratio of 50:1, by dipping the sample in the solution for half an hour at ambient temperature. To remove the extra liquor, the sample is wiped through two glass rods and then placed in between the two plates of the perspirometer under the recommended pressure of 12.5 kPa. The sample is dried in an oven at 37°C for 4 h. The rating is given as 1–5 by using the gray scale.
Color fastness to sublimation:
The color fastness of a dyed article is not only affected by washing, water, or rubbing but also by heat in many forms, such as by pressing, dry heat, or heat with moisture. Some dyes are sensitive to heat and hence can fade/bleed due to the effect of heat. This test is intended to assess resistance of color to the action of dry heat only and not by pressing. Mostly, there are two methods to evaluate color fastness to dry heat: ISO 105–P01, Color Fastness to Dry Heat (Excluding Pressing) and AATCC Test Method 117-2004-Color Fastness to Heat: Dry (Excluding Pressing). The methods are applicable to textiles of all kinds and can be conducted at different temperatures depending upon the stability of fibers, which can be influenced by chemicals used during dyeing, printing, chemical processing, and by physical factors involved in color change and staining. Nondyed fabric attached to tested samples are exposed to heat. The rating is given using the gray scale.
A specimen of the sample under test is treated with dry heat for 30 s under a specified temperature and pressure. Three temperature options are 150°C ± 2°C, 180°C ± 2°C, and 210°C ± 2°C, and it is important to mention the temperature at which the sample is exposed as it can significantly alter the results. A pressure of 4 ± 1 kPa is applied to the sample during testing. The treated specimens are conditioned and evaluated using the gray scale for color change and staining on adjacent fabric.
References:
- Advanced Textile Testing Techniques Edited by Sheraz Ahmad, Abher Rasheed, Ali Afzal, and Faheem Ahmad
- http://textilelearner.blogspot.com/2011/12/what-is-color-fastness-classification.html
- http://textilelearner.blogspot.com/2012/11/different-color-fastness-tests.html
