Overview
ISO 105-B05:1993 - Textiles - Tests for colour fastness - Part B05: Detection and assessment of photochromism - specifies a procedure to detect and evaluate reversible colour changes (photochromism) in dyed textiles. The method exposes a specimen to intense light for a short period, assesses immediate colour change with the grey scale (ISO 105-A02), then stores the specimen in the dark and reassesses to determine reversibility. Note: the biological term “phototropism” appears in older texts but photochromism is the preferred term for reversible light-induced colour change in textiles.
Key topics and technical requirements
- Scope: Designed for coloured textiles that change shade on light exposure but practically return to their original shade in the dark.
- Specimen: Minimum size 10 mm × 45 mm; can be fabric strips, wound yarns, or compressed fibre slivers.
- Light source: Xenon arc lamp with correlated colour temperature between 5500 K and 6500 K.
- Filter: Glass filter that reduces ultraviolet radiation; transparency ≥ 90% between 380–750 nm, falling to 0% between 310–320 nm.
- Reference fabrics: Use reference fabric 1 or L2 (as defined in ISO 105-B01), partially covered during reference exposure to determine time to produce a grade 4 change.
- Exposure timing: For the test specimen, expose for a fraction of the reference time - typically one quarter of the time required to produce grey-scale degree 4 on reference 1, or one twenty-fifth of the time for reference L2.
- Assessment:
- Immediately after exposure, evaluate contrast between exposed and unexposed areas using the grey scale (ISO 105-A02).
- If contrast > degree 4, condition the specimen in the dark for 1 hour at 20°C ±2°C and 65% ±2% RH.
- If contrast persists, accelerate recovery by steaming (60 s over gently boiling water) and reassess.
- Interpretation:
- Contrast ≤ 4 immediately: not photochromic.
- Contrast > 4 immediately but reduced to ≤ 4–5 after conditioning: photochromic.
- Contrast > 4–5 after conditioning: not photochromic but shows poor initial lightfastness.
- Reporting: Combine lightfastness rating (from ISO 105-B01 or B02) with a P indicator and the grey-scale evaluation, e.g., 6(P3-4) or 6-7(P2-3). Test report must identify the standard, sample details, and results.
Applications and users
- Textile manufacturers and dye houses assessing reversible light-induced colour change.
- Quality control and test laboratories verifying product conformity and lightfastness performance.
- Product developers, colour technologists, and brands for colour stability, quality assurance, and claims substantiation.
- Applicable across apparel, upholstery, technical textiles and any dyed textile where transient colour change on light exposure is a concern.
Related standards
- ISO 105-A01: General principles for colourfastness tests
- ISO 105-A02: Grey scale for visual assessment of change in colour
- ISO 105-B01 / ISO 105-B02: Lightfastness test methods (daylight and xenon arc lamp)
Keywords: ISO 105-B05:1993, photochromism, textiles, colour fastness, grey scale, xenon arc lamp, lightfastness, reference fabrics.