IWTO-47 & IWTO-62 explained: practical guides to wool fibre testing

When fibre measurements drive grading, contracts or genetics, method clarity matters. Two IWTO procedures sit at the centre of reliable results:

• IWTO-47 — measures the mean and distribution of fibre diameter using an Optical Fibre Diameter Analyser (OFDA). (member.iwto.org)

• IWTO-62 — determines fibre length distribution (true length) and diameter in wool top & slivers using the OFDA4000. (member.iwto.org)

Below is a plain-English walkthrough of what each covers (and doesn’t), how it maps to real workflows, and where OFDA 2000 and OFDA 4000 deliver the most value.

What these standards do (and don’t) cover

• They define how to measure — scope, sampling/conditioning, and reportables (e.g., mean, SD, CV, histograms). That consistency reduces operator and seasonal variation across labs. (member.iwto.org)

• They don’t replace judgement — you still choose acceptance bands (e.g., comfort factor thresholds; short-fibre limits) to suit your contracts or breeding goals. Trade bulletins stress specifying the right length method for the decision at hand. (SGSCorp)

  
  

IWTO-47: diameter & distribution, measured by OFDA

What it is The method for measuring the mean and distribution of wool fibre diameter with an Optical Fibre Diameter Analyser (OFDA). (member.iwto.org)

Why it mattersDistribution — not just the mean — drives handle, comfort factor and processing behaviour. University and lab resources show OFDA outputs such as histograms, SD, CV, comfort factor and staple traits that producers and classers use daily. (montana.edu)

Practical fit

• Shearing sheds / studs: OFDA 2000 is portable and reports histogram-level metrics for objective classing and selection. Note: OFDA2000 used in greasy staple mode does not meet IWTO TM7 requirements. (OFDA)

• Labs & service providers: OFDA workflows align with IWTO-47 reporting, enabling consistent MFD/distribution across seasons and sites. (member.iwto.org)

IWTO-62: true length distribution in tops/slivers (plus diameter)

What it isThe method for measuring true fibre length distribution and diameter in wool top & slivers using the OFDA4000. (member.iwto.org)

Why it mattersShort fibres can depress yarn strength and increase variability. IWTO-62 reports true length distribution (not hauteur) and supports derived short-fibre metrics that mills track during worsted processing. Trade guidance is clear: length methods are not interchangeable, and the chosen method must be specified. (SGSCorp)

Practical fit

• Topmakers & QA labs: OFDA 4000 automates preparation and measurement to deliver true length distribution and diameter for tops/slivers, directly supporting contract specs and process control. (OFDA)

  
  

Quick take: Use IWTO-47 with OFDA 2000 for diameter and distribution measurements on scoured or cleaned wool and for educational purposes. Use IWTO-62 with OFDA 4000 when measuring tops or slivers where both true fibre length and diameter are required.

True length vs hauteur (why they’re different)

• True length distribution (IWTO-62): Optical measurement of individual fibres in tops/slivers — informs short-fibre content and the tail of the curve. (member.iwto.org)

• Hauteur/Barbe (capacitance): Established trade measures biased by fibre cross-section or weight; useful, but not the same as true length. Bulletins recommend stating the method because results are not directly interchangeable. (SGSCorp)

Outputs you can expect (by method)

Output	IWTO-47 (OFDA)	IWTO-62 (OFDA4000)	Notes
Mean fibre diameter (MFD)	✔︎	✔︎	Both report MFD; ASTM D6466/IWTO-12 is the Laserscan route for diameter. (Antpedia)
Diameter distribution (histogram)	✔︎	✔︎	Histograms underpin comfort factor and grading. (member.iwto.org)
Comfort factor (CF)	✔︎ (reported with OFDA)	✔︎ (with diameter)	Common in producer reports and lab services. (montana.edu)
True length distribution	—	✔︎	Unique to IWTO-62/OFDA4000 for tops/slivers. (member.iwto.org)
Short-fibre metrics (derived)	—	✔︎	Used for worsted QA and risk control. (SGSCorp)

Where OFDA 2000 & OFDA 4000 add the most value

• OFDA 2000 — portable, standards-aligned diameter with distribution; widely used by universities and industry groups for classing, breeding and education. (montana.edu)

• OFDA 4000 — automated tops/slivers measurement of true length distribution and diameter per IWTO-62; suited to mills and labs managing short-fibre risk and contract specs. (OFDA)

Common pitfalls (and how to avoid them)

• Not naming the method when quoting length — hauteur vs true length can lead to mismatched specs. Always specify. (SGSCorp)

• Ignoring distribution — relying on mean alone can mask tails that affect handle or strength. IWTO-47/IWTO-62 require distribution-aware reporting. (member.iwto.org)

• Preparation/conditioning drift — follow the sampling and prep steps for your chosen method to keep results comparable. (member.iwto.org)

In Summary

In short, IWTO-47 and IWTO-62 give you a common language for reliable results: diameter and distribution with OFDA 2000, and true length distribution plus diameter in tops/slivers with OFDA 4000. Use the right method for the decision—classing and breeding, lab QA or contract compliance—and make the outputs (histograms, comfort factor, true length) standard across your team. If you’d like practical help mapping method to workflow, book a 20-minute measurement review—Australia-based support, serving mills, labs and producers worldwide.

FAQs: standards, fibre testing & fiber analysis

Is OFDA “approved” under IWTO? Yes. IWTO-47 is the method titled Measurement of the mean and distribution of fibre diameter of wool using an Optical Fibre Diameter Analyser (OFDA). IWTO-62 covers true length distribution and diameter in tops/slivers using the OFDA4000. (member.iwto.org)

How is “fiber analysis” different from routine fibre testing? “Fibre testing” usually refers to standardised outputs used for trade/selection (MFD, distribution, CF). “Fiber analysis” can be broader — microscopy, curvature, and, for tops/slivers, true length distribution — depending on the question. Keeping to recognised procedures makes cross-lab comparisons meaningful. (montana.edu)

Do producers actually use histogram-level results on farm? Yes. University and industry services provide OFDA 2000 reports with histograms, CF and staple metrics to support breeding and classing decisions. (montana.edu)

References (selection)

• IWTO Standards — IWTO-47 (OFDA diameter & distribution); IWTO-62 (true length distribution & diameter in top/sliver). (member.iwto.org)

• OFDA instruments — OFDA 2000 overview; OFDA 4000 overview and tops/slivers context. (OFDA)

• University/lab resources — Montana Wool Lab: OFDA 2000 outputs and glossary. (montana.edu)

• Length methods for trade — SGS: length bulletin on IWTO-17/30/62 and why the method must be specified. (SGSCorp)

• Laserscan context — ASTM D6466 alignment with IWTO-12 (diameter by Laserscan). (iTeh Standards)

Background reading — Woolwise materials summarising OFDA/IWTO-47 and IWTO-62 technology & standards context. (Woolwise)