A mill ships the same fabric to two customers. One specification says "AATCC 16.3, 20 AFU, grade 4 minimum". The other says "ISO 105-B02, minimum 4". The lab runs one xenon test, writes "4" on both reports and moves on.
At least one of those reports is wrong — and possibly both. The two methods use similar machines, but the number at the end means something different in each.
The number answers a different question
This is the core difference, and everything else follows from it.
| AATCC TM16.3 | ISO 105-B02 | |
|---|---|---|
| What is fixed in advance | The amount of exposure, stated in AATCC Fading Units (AFU) | The reference materials the specimen is compared with |
| What the grade is | A grey scale grade (1–5) for the colour change after that exposure | The number of the blue wool reference that shows similar fading |
| Typical specification | "20 AFU, grade 4" | "Light fastness ≥ 4 (blue wool)" |
| Scale | 5 = no change, 1 = severe change | 1 = very low fastness, 8 = very high (or L2–L9) |
So "4" under AATCC 16.3 means the fabric changed by about one grey scale step after a fixed dose. "4" under ISO 105-B02 with blue wool 1–8 means the fabric faded about as much as blue wool reference 4. A fabric can easily satisfy one and fail the other.
"AATCC 16" is not a complete reference
AATCC's light fastness test is published as separate sub-methods, of which 16.3 is the xenon-arc procedure. Within TM16.3 there are three options:
- Xenon-arc, alternate light and dark
- Xenon-arc, continuous light, black standard temperature
- Xenon-arc, continuous light, black panel temperature
A specification that says only "AATCC 16" — or "AATCC 16.3" without an option and an AFU figure — is incomplete. Ask which option and how many AFU before quoting a result.
ISO 105-B02 also has choices
ISO 105-B02:2014 offers four exposure cycles (A1, A2, A3 and B) and five exposure methods. Cycles A1 to A3 use blue wool references 1 to 8 and control effective humidity with a red azoic humidity-test fabric. Cycle B uses the American L2 to L9 references, a black standard temperature of (65 ± 3) °C or black panel temperature of (63 ± 3) °C, and (30 ± 5) % relative humidity.
An ISO specification without a cycle is therefore also incomplete, even though cycle A1 — labelled "normal" and representing a temperate climate — is the usual starting point.
Cycle B is a relative, not a substitute
Because cycle B uses the L-series references and a black-panel/black-standard regime familiar from US practice, it is tempting to treat a cycle B result as an AATCC result. Do not. The procedures, end points and report wording differ, and the buyer's contract names a specific document.
ISO 105-B01:2014 is explicit on the wider point: the results from blue wool 1–8 and L2–L9 are not interchangeable, and the correlation chart between the two sets shall not be used to convert a rating from one to the other. If two customers need two standards, run two tests.
What both methods share
The overlap is real, and it is what lets one instrument serve both:
- A filtered xenon-arc source simulating daylight.
- Control of specimen temperature with a black standard or black panel thermometer rather than chamber air temperature.
- Controlled irradiance. ISO 105-B02 specifies (42 ± 2) W/m² over 300–400 nm or (1.10 ± 0.02) W/(m²·nm) at 420 nm where irradiance control is available.
- Visual grading against a grey scale for colour change, in a controlled viewing cabinet.
The differences sit in the reference materials, the humidity control, the definition of the end point and the report.
A practical table for the lab
| Question | AATCC TM16.3 request | ISO 105-B02 request |
|---|---|---|
| Which option or cycle? | Option 1, 2 or 3 | Cycle A1, A2, A3 or B |
| How much exposure? | Number of AFU | Until the references reach the specified contrast (Methods 1–4), or a stated dose (Method 5) |
| Which references? | L-series blue wool for checking the exposure | Blue wool 1–8 (cycles A) or L2–L9 (cycle B) |
| How is it graded? | Grey scale for colour change | Blue wool number |
| What goes on the report? | Option, AFU, grade | Cycle, method, reference set, blue wool rating |
What this means when buying an instrument
If your customers ask for both methods, check that the xenon chamber can control the parameters each one needs: black standard and black panel temperature, relative humidity, irradiance at the specified band, and continuous as well as alternating light/dark operation if Option 1 is required. Budget for both sets of blue wool references and for the humidity-test control fabric — they are consumables, and a chamber without them cannot produce a valid result under either standard.
Before you sign two reports
- Does each report name the exact method — TM16.3 option, or B02 cycle and method?
- Is the AATCC result stated as AFU plus grey scale grade?
- Is the ISO result a blue wool number, with the reference set named?
- Has anyone converted one result into the other? If so, withdraw it.
TLI-TexLabInstruments manufactures xenon light fastness testers in its own workshop in Istanbul, configured for both ISO and AATCC methods.