A mill supplies the same fabric to two programmes. One buyer asks for AATCC 135, the other for ISO 5077 with ISO 6330 washing. The fabric passes one and fails the other, and the obvious question follows: which laboratory is wrong?
Usually neither. They ran two different tests that happen to share a purpose.
Same question, two systems
AATCC 135 is a self-contained method for dimensional change of fabrics after home laundering. Its scope describes a matrix of four washing temperatures, three agitation cycles and four drying procedures. Detailed machine parameters and alternative laundering conditions now sit in AATCC Laboratory Procedure LP1.
The ISO route is split across three documents: ISO 6330 does the washing and drying, ISO 3759 covers specimen preparation and measurement, and ISO 5077 brings them together.
| AATCC 135 | ISO 5077 + ISO 6330 + ISO 3759 | |
|---|---|---|
| Washing machine | Top-loading agitator, per AATCC LP1 | Usually Type A front-loading; Types B and C also defined |
| Typical fabric specimen | 380 × 380 mm with 250 mm benchmark pairs (a larger option exists) | 500 × 500 mm with marks at least 350 mm apart |
| Conditioning atmosphere | ASTM D1776 | ISO 139 |
| Detergent | AATCC standard reference detergent | ISO 6330 reference detergents 1–7 |
| Drying procedures | A tumble, B line, C drip, D screen | A line, B line drip, C flat, D flat drip, E flat press, F tumble (2021 edition) |
| Number of cycles | Traditionally three unless agreed otherwise | As specified — ISO 6330 defines one wash |
Every row is a reason why results differ. None of them is a conversion factor.
Trap 1: the same letter means different drying
Look at the drying codes. In AATCC 135, C is drip dry. In ISO 6330:2021, C is flat dry and drip drying is B or D depending on whether the specimen hangs or lies flat. "Tumble" is A in one system and F in the other.
A laboratory running both methods should never write a bare letter on a report or a worksheet. Write "AATCC 135 drying A (tumble)" or "ISO 6330 drying procedure F (tumble dry)", in words.
Trap 2: borrowing specimens between methods
It is tempting to cut one specimen size and use it for everything. AATCC 135 itself warns that results may not be comparable when different specimen sizes, benchmark lengths or numbers of benchmarks are used. A 250 mm gauge length and a 350 mm gauge length do not carry the same measuring error, and smaller specimens behave differently in a large load.
Cut to the size the method specifies, and record the specimen size and benchmark distance on the report.
Trap 3: one conditioning room for both
ISO 139 and ASTM D1776 do not define the same atmosphere, and D1776 has been revised more than once. A room set up for ISO 139 is not automatically correct for an AATCC test. If you run both systems, check the edition of D1776 your customer cites, and make sure your cabinet or room can hold both set points — or decide which one each programme accepts in writing.
Trap 4: the "equivalent machine"
AATCC methods are written around top-loading agitator machines with defined water levels, agitation speeds, wash times and spin speeds. A front-loading drum cannot reproduce that action, however carefully it is programmed.
The reverse also holds. ISO 6330 does describe a top-loading agitator machine (Type B), but an AATCC machine can only run ISO 6330 within the conditions defined for that machine type. A Type B ISO result is still not a Type A ISO result.
Trap 5: comparing different numbers of cycles
AATCC 135 has traditionally reported shrinkage after three washing and drying cycles unless another number is agreed. Many ISO-based specifications call for one wash, or one plus a tumble dry, or five. Shrinkage often continues over the first few cycles, so a three-cycle AATCC result and a one-cycle ISO result for the same fabric should not be expected to match.
What to do in practice
- Test to the specification each buyer actually wrote. Do not substitute one method for the other because the machine is free.
- Report the full condition set: method, edition, machine type, cycle, temperature, drying procedure in words, load, number of cycles, specimen size.
- If a buyer asks for a "comparison", run both methods in parallel on specimens from the same area of the same piece and present the results side by side — not one converted into the other.
- Keep separate worksheets for AATCC and ISO tests, with the drying codes printed in words.
Equipment note
For AATCC testing, our top-loading AATCC shrinkage washing machine comes with AATCC LP1 programmes preloaded, and the matching AATCC tumble dryer offers Normal, Delicate and Permanent Press programmes with method-controlled exhaust temperature. For ISO 6330 work we build a front-loading laboratory reference washing machine and a precision tumble dryer; all of them are produced in our own workshop in Istanbul.