Determination of Color Fastness to Light in Hardshell Jackets: Standards, Test Methods and Grading

Color fastness to light is one of the most critical durability indicators for hardshell jackets, as these outdoor garments face prolonged exposure to sunlight and ultraviolet radiation during use. This article explains how light fastness of hardshell jacket fabrics is determined in accordance with ISO 105-B02, GB/T 8427 and related standards, covering specimen preparation, xenon arc exposure procedures, blue wool reference grading, and acceptance criteria under the Chinese product standard GB/T 32614. It serves as a practical technical reference for textile manufacturers, quality engineers, and buyers sourcing weatherproof outdoor apparel.

Technical Overview

Color fastness to light, commonly referred to as light fastness, quantifies the ability of dyed, printed, or coated textiles to resist fading or color change when exposed to sunlight or to an artificial light source that simulates solar radiation. Hardshell jackets are engineered for demanding outdoor environments where they are subjected to intense and repeated ultraviolet (UV) and visible light exposure. Poor light fastness leads to visible fading, color mismatch between panels and trims, and premature aging of the garment surface, all of which directly affect product appearance and perceived quality.

Light fastness is therefore a mandatory performance parameter in the Chinese national product standard GB/T 32614, which specifies requirements for outdoor sports hardshell apparel, as well as in most international brand performance specifications. Testing is typically performed by accredited third-party laboratories using a xenon arc fading lamp, with results graded against blue wool reference fabrics on a scale of 1 to 8, where grade 8 represents the highest resistance to fading. Depending on the product quality classification, GB/T 32614 generally requires light fastness grades in the range of 3-4 to 4-5, and many commercial specifications set grade 4 as the minimum acceptance threshold for shell fabrics.

Testing Samples

Shell Fabric Specimens

Specimens are cut from representative body panels of the finished hardshell jacket or from bulk production fabric of the same dye lot. Each distinct color zone must be sampled separately. Following the requirements of ISO 105-B02 and GB/T 8427, each specimen should measure at least 20 mm x 45 mm, be free from creases and wrinkles, and be mounted on inert white cardboard backing. Prints, patterns, and coated surfaces must be tested exactly as they appear on the finished garment, without any surface preparation.

Composite and Laminated Constructions

Most hardshell jackets use two-layer or three-layer laminates consisting of a face fabric, a waterproof-breathable membrane, and, in three-layer constructions, a protective scrim or tricot backing. These materials must be tested as a complete composite rather than as separated components, because the membrane, adhesives, and finishing agents can influence photodegradation behavior. The face fabric side, which is the light-exposed surface in actual wear, is oriented toward the light source during exposure.

Trims, Zipper Tape and Decorative Elements

Colored zipper tape, piping, binding, seam tape, embroidered or heat-transferred logos, hook-and-loop fasteners, and lining fabrics should be sampled whenever they contribute to the visible appearance of the garment. Because trims are frequently dyed with different dye classes than the shell fabric, they may fade at different rates, producing unacceptable color mismatch even when the main fabric passes. Small or non-self-supporting components are mounted on suitable inert backing to ensure a flat, reproducible exposure surface.

Testing Items

The core test item for hardshell jackets is color fastness to light, expressed as the change in color of the exposed specimen relative to an unexposed portion of the same specimen. Depending on the purpose of testing, the scope may be extended to include:

• Color fastness to artificial light using a xenon arc fading lamp (change in color), tested to ISO 105-B02 or GB/T 8427.
• Color fastness to daylight exposure behind glass, tested to ISO 105-B01 or GB/T 8426 as a reference or arbitration method.
• Light fastness of printed patterns, transfer logos, and coated or calendared surfaces.
• Light fastness of trims and accessories relative to the shell fabric, evaluated for color consistency.
• Light fastness determined after laundering or other pre-treatments, where the relevant specification requires it.

Within the full assessment framework of GB/T 32614, light fastness is evaluated alongside companion color fastness properties such as fastness to rubbing, perspiration, water, and washing, so that the complete color performance profile of the jacket can be verified in a single test program.

Testing Methods

Xenon Arc Lamp Method (ISO 105-B02 / EN ISO 105-B02 / GB/T 8427)

The xenon arc method is the dominant industrial procedure because it provides accelerated, controlled, and reproducible exposure conditions. A xenon arc burner fitted with suitable daylight filters produces a spectral distribution closely matching sunlight transmitted through window glass. Typical operating parameters include an irradiance of 42 W/m² in the 300 nm to 400 nm band, or 1.10 W/m² at 420 nm, a black standard thermometer temperature of approximately 50 °C, and controlled relative humidity inside the exposure chamber. Effective humidity is validated using standard control fabrics to ensure comparability between test runs.

The specimen and a set of blue wool reference fabrics are mounted in holders, and a portion of each is covered with an opaque masking card so that an unexposed area remains available for comparison. Exposure proceeds until the endpoint defined by the selected method is reached, most commonly the point at which the specimen exhibits a color change corresponding to gray scale grade 4, or the point at which a specified blue wool reference shows a defined level of fading. The exposed specimens are then conditioned in a standard atmosphere before evaluation.

Daylight Exposure Method (ISO 105-B01 / GB/T 8426)

In the daylight method, specimens and blue wool references are exposed outdoors behind glass, oriented toward the equator, with portions masked for control comparison. Because solar intensity and spectrum vary with season, latitude, and weather, this method is slow and results are strongly influenced by climate. It is mainly used as a reference or arbitration technique when correlation with natural conditions is required, rather than for routine production control.

AATCC 16 Option for North American Markets

For products destined for North American markets, AATCC 16 defines several xenon arc and carbon arc exposure options. A widely used xenon option employs continuous illumination with a black panel temperature of 63 °C and controlled relative humidity, and specimens are graded against AATCC blue wool lightfastness standards. Because the exposure cycles, references, and rating conventions differ, AATCC results are not directly interchangeable with ISO or GB/T results, and the applicable specification must be confirmed before testing begins.

Evaluation and Grading

After exposure and conditioning, specimens are assessed in a color matching cabinet under standard illuminant D65 by trained observers. The permanent color change of the exposed area is compared with the fading of the blue wool references, and the fastness grade is reported as the number of the blue wool reference that shows a comparable visible change. Half-step grades such as 4-5 are permitted, and results may be reported as minimum values, for example grade 4 or higher. For compliance with GB/T 32614, the reported grade must meet or exceed the minimum value assigned to the product quality classification, with higher classifications demanding correspondingly higher light fastness performance.

Applications

Light fastness determination supports the entire product life cycle of hardshell jackets, from material development to market surveillance:

• Dye, pigment, and laminate selection during fabric research and development, enabling suppliers to engineer color systems that withstand prolonged outdoor exposure.
• Factory quality control and incoming material inspection, ensuring that each production batch of shell fabric and trims meets the specified minimum grade.
• Compliance verification against GB/T 32614 for products sold in China, and against ISO or AATCC based specifications for export markets in Europe, North America, and Asia.
• Certification and marketplace testing programs conducted by accredited third-party laboratories, providing authoritative test reports for brands, retailers, and regulatory submission.
• Failure analysis and consumer complaint investigation, where fading complaints are diagnosed by reproducing exposure under controlled conditions and comparing performance against the original specification.

FAQ

What light fastness grade is required for a hardshell jacket to pass?

Under GB/T 32614, the minimum acceptable grade depends on the declared product quality classification, with typical requirements ranging from grade 3-4 to grade 4-5. In commercial practice, most brand specifications require at least grade 4 for the shell fabric, and vivid or dark colors that are more sensitive to fading are often assigned stricter internal limits.

Why are blue wool references used instead of simply reporting exposure hours?

Exposure hours alone cannot be compared between different instruments, lamp conditions, or laboratories, because irradiance, temperature, and humidity vary. Blue wool references fade alongside the specimen and act as an internal dosimeter, allowing the light dose actually received by the specimen to be expressed as a grade that is reproducible across laboratories and test conditions.

How long does a xenon arc light fastness test take?

Test duration depends on the target grade and the selected exposure cycle. To demonstrate a grade of 4 or higher, exposure typically requires several tens of hours of machine operation, while verification of very high grades approaching 7 or 8 can extend beyond one hundred hours. The laboratory confirms completion by checking the specimen and references against the defined endpoint before grading.

Should the membrane side and lining be tested as well?

The face fabric is the primary test object because it receives direct sunlight in wear. However, colored linings, mesh panels, and visible trim tapes should also be tested when the product specification covers the whole garment, since differential fading between adjacent components is a common source of consumer dissatisfaction.

Can one specimen represent all colors of the jacket?

No. Light fastness is determined by the dye class, depth of shade, and fiber composition, so every distinct color, print area, and trim material must be sampled and tested individually. A jacket is considered conforming only when all tested components meet the specified minimum grade.