Color fastness testing generally includes light fastness, weather fastness, wash fastness, rub fastness, perspiration fastness, etc. Sometimes, there are special color fastness requirements for different textiles or usage environments. Typically, in color fastness tests, the degree of color change of the dyed material and the degree of color transfer to the lining material are evaluated. Except for light fastness, which is graded on an eight-level scale, the rest are usually graded on a five-level scale. A higher level indicates better color fastness.

This article mainly focuses on wash fastness testing. Wash fastness, also known as detergent fastness or soap fastness, refers to the ability of textiles to maintain their original color under washing conditions, that is, their ability not to fade or change color. Washing is one of the most common methods of garment care, and wash fastness simulates the degree of color fastness of textiles in different detergent and washing environments. There are various methods for wash fastness testing. The basic principle is to simulate domestic or commercial washing conditions, where the test samples undergo agitation, rinsing, and drying under a specified time and temperature conditions, and then the color change of the samples and the color transfer to the lining fabric are evaluated against a grayscale card or instrument. There may be some differences among various methods regarding temperature, test solution, washing procedure, addition of steel balls, and drying procedure.

Testing Principle

The wash fastness test involves affixing textile samples to one or two specified lining fabrics, immersing them in a soapy solution, subjecting them to mechanical agitation, followed by rinsing and drying under specified time and temperature conditions. The degree of color change of the samples and the color transfer to the lining fabric is evaluated against a grayscale card. There are five test methods for wash fastness, primarily differing in test temperature and time, with other aspects being largely similar.

Testing Standards

ISO 105-C01-C05-1989 “Textiles – Tests for Colour Fastness – Part C: Colour Fastness to Washing: Tests 1 to 5” EN 20105C01-C05-1992 “Textiles – Tests for Colour Fastness – Part C: Colour Fastness to Washing: Tests 1 to 5” DINEN 20105C01-C05-1993 “Textiles – Tests for Colour Fastness – Part C: Colour Fastness to Washing: Tests 1 to 5” AATCC 172-2002 “Test Method for Colorfastness of Fabrics to Household Laundering Using Oxygen Bleach” GB/T 3921.1-5-1997 “Textiles – Tests for Colour Fastness – Part C: Colour Fastness to Washing: Tests 1 to 5” ISO 105-C01-C05 specifies several test methods for wash fastness, covering a range from mild to severe washing operations. It remains widely used as a classic color fastness test method. Among them, the ISO 105-C03 method is used for testing the wash fastness of all-cotton fabrics, and the Chinese standard GB/T3921.3-1997 is based on this method with no technical differences from the international standard, applicable to any form of textiles. In addition to these standards, there are many other international standards for testing the wash fastness of textiles, such as the British BS 1006-C01 and the Japanese JISL 0844.

Testing Methods

(1) Chinese Standard (GB/T 3921.3-1997) A 4cm × 10cm sample is taken, with its front side in contact with a 4cm × 10cm multicomponent lining fabric, sewn along one short edge to form a composite sample, which is then placed in a stainless steel container with a capacity of (550±50)mL [(diameter (75±5)mL, height (125±10)mL)], and filled with soapy solution preheated to (60±2)°C to achieve a bath ratio of 50:1. The composite sample is treated at (60±2)°C for 30 minutes, then removed, rinsed twice with cold distilled water, and rinsed for 10 minutes in flowing cold water. After removing excess water, the composite sample is unfolded to hang dry in air not exceeding 60°C. Once dry, the composite sample is evaluated against a gray scale card for color change and staining of the lining fabric. (2) American Association of Textile Chemists and Colorists Standard (AATCC 61A-2003) A 50mm × 100mm sample is taken, with its front side in contact with a 5mm × 100mm multicomponent lining fabric, sewn along one short edge to form a composite sample, which is then placed in a stainless steel container with a capacity of (550±50)mL [(diameter (75±5)mL, height (125±10)mL)], and filled with soapy solution preheated to (40±2)°C to achieve a bath ratio of 200mL. The composite sample is treated at (40±2)°C for 45 minutes, then removed, rinsed three times with distilled water at (40±3)°C for 1 minute each, and excess water is removed. The composite sample is unfolded to hang dry in air not exceeding 71°C. Once dry, the composite sample is evaluated against a gray scale card for color change and staining of the lining fabric. (3) Japanese Industrial Standard (JISL 0844-2005) A 4cm × 10cm sample is taken, with its front side in contact with a 4cm × 5cm cotton lining fabric and a 4cm × 5cm nylon lining fabric respectively, sewn along one short edge to form a composite sample, which is then placed in a stainless steel container with a capacity of (550±50)mL [(diameter (75±5)mL, height (125±10)mL)], and filled with soapy solution preheated to (50±2)°C to achieve a bath ratio of 50:1. The composite sample is treated at (50±2)°C for 30 minutes, then removed, rinsed twice with cold distilled water, rinsed for 10 minutes in flowing cold water, and excess water is removed. The composite sample is unfolded to hang dry in air not exceeding 60°C. Once dry, the composite sample is evaluated against a gray scale card for color change and staining of the lining fabric.

Testing Procedure

Here, we will introduce the testing process using GB/T 3921-2008 “Textiles – Tests for Colour Fastness – Colour Fastness to Soaping” as an example:

1. Sample Preparation:

A sample of 100mm x 40mm is taken, with the face in contact with a 100mm x 40mm multi-fiber lining fabric, sewn along one short edge to form a composite sample.

Alternatively, a sample of 100mm x 40mm is taken, sandwiched between two 100mm x 40mm single-fiber lining fabrics, sewn along one short edge to form a composite sample. If the sample is a blend or interwoven fabric, one piece is made of the fiber with the highest content, and the second piece is made of the fiber with the lower content.

2. Preparation of Test Solution

For tests A and B, prepare a solution with 5 grams of standard soap per liter of distilled water. For tests C, D, and E, prepare a solution with 5 grams of standard soap and 2 grams of anhydrous sodium carbonate per liter of distilled water.

3. Testing

Place the composite sample and the specified number of steel balls in a container, pour in the preheated test solution to the required volume at the test temperature ±2°C, achieving a bath ratio of 50:1. Close the container, adjust the temperature and time according to the standard, and start the machine. Timing starts from when the container is closed. The WashTrue washing fastness tester, equipped with SmartFill intelligent liquid filling technology, ensures precise and efficient testing. It features a touch screen interface for easy operation, intelligent temperature control algorithms for reliable results, and multiple safety designs for long-term, low-noise operation.

4. Rinsing and Drying

After washing, remove the composite sample from the container, rinse it twice in distilled water, then rinse with flowing cold water until clean. Squeeze out excess water, unfold the composite sample, leaving only the seam connecting the sample, and place it flat between two unused filter papers to remove excess moisture. Then hang it to dry in air not exceeding 60°C.

Test Results

Each sample is assessed for color change and staining of the lining fabric using either instruments or gray scale cards. The degree of fading or staining should be tested under specified light sources and rated according to a standard gray card, with results graded on a scale of 1 to 5, with 5 being the best and 1 being the worst. Instrument grading involves calibrating against the standard reflectance of a known specification whiteboard, measuring the spectral power distribution of the sample’s reflected light or its own reflectance characteristics, and then calculating the three influencing values, chromaticity coordinates, CIELAB uniform color space, etc., based on the spectral measurement data. These values are then converted into gray card ratings for color change and staining fastness through a series of formulas.

Gray scale card ratings are divided into color change and staining scale cards, each with five levels and nine grades. When rating, the illumination conditions should be sunny daylight (9:00~15:00) or an equivalent light source with an illumination of 6001x or above. The observer’s line of sight and the fabric surface should form an angle of approximately 5 degrees, with the observation direction roughly perpendicular to the fabric surface. Gray scale cards are used to rate color changes and staining levels of the test samples.

Error Analysis in Testing

• Differences in multi-fiber lining fabrics can cause testing errors. The same sample and method may yield different results when using different multi-fiber lining fabrics for staining tests. Variations in the fabric structure, composition, yarn count, density, and finishing process of multi-fiber lining fabrics directly impact their staining performance and ultimately influence test results.
• Prolonged evaluation of color fastness samples under standard light sources in a lightbox can cause eye fatigue, affecting the accuracy of assessments.

• During rating, the angle of illumination from the light source should be 40 degrees to the sample surface, with the observer’s line of sight perpendicular to the sample surface and a distance of 30-40cm for optimal viewing, as deviation may affect assessment results.
• The cleanliness of loose fibers attached to the lining fabric’s surface also affects assessment results.

Conclusion

Significant differences exist in the wash fastness values obtained according to different national testing standards. Compared to the standards of the United States and Japan, the testing requirements for wash fastness of textiles under the Chinese standard are stricter. This edition primarily focused on the wash fastness testing of textiles. For more knowledge on color fastness testing, please like and follow us for timely updates. For more textile testing knowledge, instrument knowledge, and textile testing laboratory knowledge, please feel free to contact us:

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