What Is Light Fastness?
In the colour fastness to light test, the sample is exposed to light under controlled conditions with a xenon arc lamp. Assessment is made comparatively with a blue wool reference scale placed alongside the sample: whichever reference's fading matches the sample's fading gives the fastness grade.
Purpose of Light Fastness
The purpose is to assess how well the product retains its colour under sunlight or shop-window lighting. It is a decisive parameter for curtain, upholstery and automotive interior textiles.
Which Products Is Light Fastness Applied To?
- Curtain and upholstery fabrics
- Automotive interior textiles
- Outdoor textiles and awnings
- Shop-window and display products
- Carpet and floor textiles
In Which Sectors Is Light Fastness Used?
Standards Related to Light Fastness
- ISO 105-B02 (colour fastness to artificial light — xenon arc)
- ISO 105-B06 (colour fastness to artificial light at high temperature and weathering)
- ISO 105-A02 (grey scale for assessing change in colour)
- AATCC 16 (colour fastness to light)
Light Fastness Conditions
- Light source
- Xenon arc lamp and defined filter system
- Reference
- Blue wool scale; exposed to the same condition as the sample
- Climate
- Black panel temperature and relative humidity are defined in the standard
- Time
- until the target level of the reference scale fades out.
Equipment for Light Fastness
- Xenon arc light fastness tester
- Blue wool reference scales
- Sample holder and mask plates
- Irradiance and temperature control system
- Light box and grey scale
Sample Requirements for Light Fastness
- The sample must be taken so as to represent the batch or production run.
- Sample description, material type, and production direction if any, must be stated.
- The standard to be applied and any customer specification must be provided together with the sample.
- The test may be destructive; the required number of samples must be confirmed in advance.
- Surfaces that will be tested must be protected during transport.
Duration of Light Fastness
High fastness grades require long exposure; the test can take days. Duration increases significantly as the target grade rises.
Light Fastness Procedure
- 1The sample and blue wool scale are placed together in the holders.
- 2A portion is covered with a mask to preserve a comparison area.
- 3The instrument is run under the defined climate conditions.
- 4Fading of the reference scale is monitored.
- 5Exposure is stopped when the target step has faded.
- 6Masked and unmasked areas are compared.
- 7The sample's fastness grade is determined by its blue wool equivalent.
Light Fastness Acceptance Criteria
The method standard defines how the test is performed, not what the result must be. The acceptance limit comes from the material or product standard, the customer specification, or the relevant regulation; this page therefore does not give a numerical limit.
Evaluation of Results
The result is given as a grade from 1 (very low) to 8 (very high) on the blue wool scale. The acceptance grade comes from the specification according to the product's use: expectation for a curtain fabric is markedly higher than for underwear.
Light Fastness Report
- Sample description, material/product information, and batch number if any
- Sample preparation method and conditioning conditions
- Standard and test conditions applied
- Instrument used and calibration status
- Measurement results and units
- Measurement uncertainty (if requested)
- A statement that the result applies only to the specimen submitted for testing
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- Harmonised standards applied according to the product family
- EU 765/2008 (market surveillance and accreditation framework)
- Relevant product regulations and customer specifications
Tekstil Testleri — What Does This Testing Field Cover?
The section below describes the field that the Light Fastness test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Textile testing answers two questions separately: does the fabric hold up physically over its service life, and does it carry any substance restricted for human health? These two axes require different laboratory infrastructure and different decision mechanisms.
On the physical side, breaking and tear strength, abrasion resistance, pilling, dimensional change, colour fastness and water and oil repellency are measured. Most of these tests depend on the USE SCENARIO: Martindale abrasion cycles are decisive for an upholstery fabric, while dimensional change in washing and colour fastness come to the fore for a shirting fabric. The same fabric goes through a different test set for a different use.
Colour fastness is a body of work of its own in this field and is not a single test. The fastness of the same fabric to light, washing, rubbing, perspiration, saliva, chlorinated water and ironing is measured separately; each represents a different moment of use. Results are rated from 1 to 5 on the grey scale and the specification gives a separate minimum rating for each agent.
On the chemical side, aromatic amines released from azo dyes, formaldehyde, heavy metals, phthalates, short-chain chlorinated paraffins, alkylphenols and PFAS compounds are screened. These items come from REACH restrictions, brand restricted substance lists (RSL) and voluntary schemes such as OEKO-TEX. Brand lists are often stricter than legislation; the target customer is decisive.
There is NO CE marking on consumer textiles. The obligation has three legs: fibre composition and care labelling, compliance with chemical restrictions, and general product safety. Textiles claiming a protective function (workwear, flame-resistant clothing, high-visibility clothing) fall under personal protective equipment legislation, where CE is mandatory — this distinction is commercially critical.
Verifying the label declaration is the most routine work in the field. Quantitative fibre analysis confirms the blend ratio stated on the label; tolerance ranges are defined in legislation. An incorrect fibre declaration both misleads the consumer and affects customs classification.
Sustainability claims have added a new body of work to the field in recent years: verification of recycled content (GRS, RCS), organic content (GOTS), restriction of harmful chemicals and water/energy footprint declarations. These claims now require auditable evidence.
Method groups in this field
Strength and durability
Strip and grab breaking strength, tearing by the Elmendorf and tongue methods, seam strength, bursting strength.
Abrasion and surface
Martindale and rotary platform abrasion, pilling and fuzzing, fabric mass and thread density measurements.
Dimensional stability
Dimensional change in washing and drying, wrinkling behaviour, appearance after ironing.
Colour fastness
Fastness to light (xenon), washing, rubbing, perspiration, saliva, water and chlorinated water; rating on the grey scale.
Functional properties
Water repellency (spray test), oil repellency, waterproofness, air permeability, effectiveness of antibacterial finishes, UV protection factor.
Chemical analyses
Aromatic amines from azo dyes, formaldehyde, pH, heavy metals, phthalates, chlorinated phenols, PFAS and alkylphenols.
Commonly confused in this field
- A brand restricted substance list (RSL) may be stricter than legislation; REACH compliance does not mean compliance with the customer specification.
- Textiles claiming a protective function fall under PPE legislation and require CE; an ordinary textile test report does not satisfy that file.
- Colour fastness is not a single number; a rating cannot be interpreted without stating which agent it relates to.
- A result obtained for a fabric does not cover the whole garment made from it; lining, sewing thread, print and trims are assessed separately.
- Performance claims after washing are valid together with the stated number of wash cycles; the word "permanent" on its own is not verifiable.
Which decisions these results support
- Compliance with the brand restricted substance list (RSL)
- Verification of label declarations: fibre composition and care instructions
- Determining the performance class of upholstery and technical textiles
- Pre-import shipment inspection and lot acceptance
- Supporting sustainability and recycled content claims
Related Tests
Frequently Asked Questions About Light Fastness
What is the blue wool scale?
It is eight reference dyed wool strips with known, progressively increasing resistance to light. The sample is exposed under the same conditions as these references, making the comparison independent of the exposure conditions.
Is it the same as UV ageing?
Their purposes differ. Colour fastness to light grades the fading of colour; UV ageing also covers the material's general degradation (cracking, mechanical loss).