Color Fastness
Color fastness is the ability of a textile material, like fabric or yarn, to retain its color without fading, bleeding, or transferring when exposed to external factors such as washing, light, rubbing, perspiration, and chemicals. It’s a key measure of a fabric’s durability and quality, ensuring that the color remains consistent and vibrant over time and with use.
We also can say, color fastness is the resistance of a dyed or printed fabric to color change or transfer when exposed to different conditions like washing, sunlight, friction, or chemicals. High color fastness means the fabric retains its color and appearance over time.
Why Color Fastness Matters:
In textiles, color fastness is a crucial quality indicator. It determines how well the fabric maintains its appearance after exposure to environmental and mechanical factors. Poor color fastness can lead to fading, staining of other clothes, and customer dissatisfaction, especially in fashion, home textiles, and industrial fabrics.
Some Important Tests:
Color Fastness to Washing (ISO 105-C06): This is a standardized test method used to determine how well a dyed or printed textile resists color fading and bleeding when washed under specific conditions. It’s part of the ISO 105 series of tests for evaluating color fastness.
Objective:
To assess the resistance of a fabric’s color to washing in water, with detergent and agitation, replicating typical home or industrial laundering conditions.
Testing Procedure:
Sample Preparation:
- A fabric specimen is cut and attached to an undyed adjacent fabric (like cotton or polyester) to observe possible staining.
Washing:
- The sample is washed in a solution of detergent and water at a specified temperature (like 40°C, 50°C, or 60°C) for a set duration (typically 30 minutes).
- Mechanical agitation replicates real-world washing conditions.
Rinsing and Drying:
- After washing, the fabric is rinsed and dried, usually air-dried or tumble-dried at a controlled temperature.
Evaluation:
- Color Change: The degree of fading is compared against a grey scale (a standard tool for assessing color changes).
- Staining: The amount of dye transferred to the adjacent undyed fabric is also evaluated using a grey scale for staining.
Grading:
( Results are graded from 1 to 5 )
- No color change or staining (excellent fastness)
- Severe color change or heavy staining (poor fastness)
Color Fastness to Light (ISO 105-B02): This is an internationally recognized test method used to determine how well a dyed or printed textile resists fading when exposed to light, particularly simulated sunlight or artificial light. It’s part of the ISO 105 series of tests for evaluating color fastness.
Objective:
To assess the resistance of a fabric’s color to fading when exposed to a controlled light source over a specific duration.
Testing Procedure:
Sample Preparation:
- A fabric specimen is cut and prepared for exposure to light.
Light Exposure:
- The sample is placed in a lightfastness testing machine (like a xenon arc lamp) that simulates natural sunlight.
- It’s exposed for a set duration under controlled conditions of temperature and humidity.
Reference Standard:
- Alongside the sample, a set of blue wool standards (ISO Blue Wool Scale) is exposed. These standards fade at a known rate and help compare the sample’s performance.
Evaluation:
- After exposure, the fabric’s color change is compared to the original using a Grey Scale for Color Change or against the blue wool standards.
Grading:
Results are measured on a scale of 1 to 8:
- Excellent light fastness (no fading)
- Very poor light fastness (severe fading)
Color Fastness to Rubbing (ISO 105-X12): This test evaluates how well a fabric resists color transfer (or staining) when rubbed, either when dry or wet. It measures the durability of the dye on the textile and its potential to stain other materials or surfaces through friction, which is a common occurrence in everyday wear (e.g., clothing rubbing against skin, furniture, or other fabrics).
Objective:
To assess the resistance of the fabric’s color to rubbing, determining how much color might transfer to another material, such as a white cloth or the skin, during normal use. This is especially important for clothing, upholstery, and footwear.
Testing Procedure:
Sample Preparation:
- A specimen of the dyed or printed fabric is prepared for testing.
- A white rubbing cloth (typically cotton) is used for the test.
Rubbing Action:
- The sample fabric is firmly rubbed against the white cloth. The rubbing can be either dry or wet, simulating different conditions.
- Dry rubbing: Simulates normal wear without moisture.
- Wet rubbing: Simulates conditions where moisture (like sweat or rain) is present.
Rubbing Parameters:
- The test is performed using a specific rubbing device (such as a Martindale Abrasion Tester) that measures both the pressure applied during rubbing and the number of rubs (usually around 10 to 20 rubs).
- The rubbing is done in a specific direction (typically back and forth) to ensure consistency.
Evaluation:
- After rubbing, the amount of dye transferred to the white rubbing cloth is evaluated.
- The extent of color change in the fabric is also measured.
- Grading is done using the Grey Scale for Color Change (to assess fabric fading) and the Grey Scale for Staining (to assess how much dye has transferred to the rubbing cloth).
Grading:
( Results are graded on a scale from 1 to 5 )
- No color transfer or staining (excellent fastness).
- Severe color transfer and staining (poor fastness).
Color Fastness to Perspiration (ISO 105-E04): This test evaluates how well a fabric retains its color when exposed to sweat, which can be acidic or alkaline. Perspiration can cause dyes to fade or transfer to other materials, especially in clothing worn for prolonged periods, like sportswear or uniforms. The test helps ensure that garments will not lose their color or stain the skin or other clothing due to exposure to sweat.
Objective:
To assess the resistance of a dyed or printed textile to color change or staining when exposed to simulated perspiration (both acidic and alkaline), reflecting real-life wear conditions.
Testing Procedure:
Sample Preparation:
- A specimen of the dyed or printed fabric is cut and prepared for testing.
- The sample is placed in contact with cotton fabric (or another reference material) to assess staining.
Simulated Perspiration:
- Two types of simulated perspiration are used:
- Acidic perspiration: Mimicking human sweat, which typically has a slightly acidic pH (around 4 to 5).
- Alkaline perspiration: Simulating sweat that has a higher pH (around 8 to 9), which can be relevant for certain skin conditions or sweat compositions.
The perspiration solution is applied to the fabric under controlled conditions of temperature (typically around 37°C to mimic body temperature) and pressure.
Exposure:
- The fabric is subjected to simulated perspiration for a defined period (usually 30 minutes to 1 hour).
- The fabric is pressed against a specific weight to simulate the pressure between fabric and skin.
Evaluation:
- After exposure to the perspiration solution, the fabric is evaluated for color change and staining.
- Color Change: The degree of fading or color alteration is assessed using a Grey Scale for Color Change.
- Staining: The amount of dye transferred to the adjacent cotton fabric (or reference material) is evaluated using a Grey Scale for Staining.
Grading:
( Results are graded on a scale from 1 to 5 )
- No color change or staining (excellent fastness).
- Severe color change or heavy staining (poor fastness).