Measuring hemp fibre fineness and length: a practical OFDA workflow

Hemp is back in the spotlight for textiles, nonwovens and composites. Yet labs and mills still face a basic problem: how to measure fineness and length consistently. Unlike wool, bast fibres lack a single, trade-standard method that everyone follows for micron/width and true length distribution. Recent reviews emphasise fragmented methods, challenging sample prep, and inconsistent outputs. (MDPI)

This guide summarises what’s commonly measured today, where the gaps are, and a practical, OFDA-based workflow you can use now—while clearly noting what’s standardised and what isn’t.

Why fineness & length matter (textiles, nonwovens, composites)

• Fineness/width influences handle, spinning performance and specific strength. (ScienceDirect)

• Length distribution and short-fibre content affect yarn strength/evenness and process losses; for nonwovens/composites they impact web formation and fibre–matrix behaviour. (Reviews repeatedly flag hemp’s high length variability as a measurement challenge.) (MDPI)

Today’s testing landscape (what’s actually used)

• Diameter/width: Many labs rely on digital microscopy/image analysis (e.g., Keyence VHX) to measure width of single fibres or bundles; there’s no universally adopted hemp diameter standard in textiles. (Wilson College of Textiles)

• Length/width distributions: Image-analysis systems derived from ISO particle techniques (e.g., ISO 13322 workflows) are used for bast fibre length/width distributions in some labs. (Wilson College of Textiles)

• Industry context: Hemp standards exist for insulation mats/boards (ISO 24260) but these address finished products—not fibre fineness/length for spinning QA. (ISO)

• Research directions: Recent reviews survey manual, capacitive and optical methods; all highlight sample preparation as the rate-limiting step for bast fibres. (MDPI)

Takeaway: Methods are evolving. If you need consistent, distribution-level data for production decisions, align your lab to an optical, image-based workflow with clear SOPs and reporting.

Where OFDA fits (and what’s proven)

• OFDA 2000 (portable/bench) measures diameter/width distributions from images of many fibres; long used in animal fibres and adopted in bast-fibre research to estimate fineness via width on degummed hemp. (SGSCorp)

• OFDA 4000 (automated sliver/top) measures true length distribution and diameter for wool tops/slivers under IWTO-62. While IWTO-62 is a wool method, its true-length, distribution-first approach is directly relevant to bast-fibre QA, where distribution tail control matters. (This is an inference about methodological fit; IWTO-62 itself is not a hemp standard.) (Woolwise)

A practical OFDA workflow for hemp & flax (step-by-step)

Designed for R&D and production labs needing repeatable, distribution-aware results. Adapt the prep to your material (decorticated, scutched, carded).

1. Define the question

   • Spinning/nonwoven/composite? Needed outputs: width (fineness) distribution, length distribution, optional short-fibre metric. Reviews recommend choosing methods that reflect final use. (MDPI)

2. Sample preparation

   • Open gently to separate fibres without creating artefacts (bast fibres are brittle; aggressive opening biases width/length). (ResearchGate)

   • Prepare snippets/beards suitable for optical capture (similar to wool optical prep, adapted to bast fibre stiffness and residual gum). (MDPI)

3. Fineness/width (OFDA 2000)

   • Capture images of many single fibres; report width distribution (proxy for fineness) across thousands of measurements. Research has correlated OFDA-measured width with residual gum content in degummed hemp, noting non-circular cross-sections. (SGSCorp)

4. Length distribution (OFDA 4000)

   • For sliver-like preps, measure true length distribution across large counts; report percentiles and a short-fibre% tailored to your process. Methodology mirrors IWTO-62 concepts for wool; apply with clear lab notation that this is a bast-fibre adaptation. (Woolwise)

5. Reporting

   • Always publish histograms (width and length), not just means; include spread (SD, CV) and the chosen short-fibre threshold. Bast-fibre reviews stress the danger of relying on averages. (MDPI)

6. Governance & lab notes

   • State exact method (instrument, prep, analysis settings). Many labs currently reference ISO 13322-style image analysis for length/width until hemp-specific test methods are harmonised. (Wilson College of Textiles)

Reading the results (what to look for)

• Width distribution: Track the tail at the coarse end; wide spreads complicate spinning and composite wet-out. (MDPI)

• True length distribution: Focus on short-fibre content and P10/P50/P90. High short-fibre% often predicts elevated waste and weaker yarns (principle widely recognised in length-distribution literature). (MDPI)

• Process control: Compare distributions before/after scutching/combing; scanner-based image analysis studies show agronomic and harvest choices shifting fineness distributions—expect similar sensitivity in your line. (ScienceDirect)

Limitations & transparency (so your buyers trust the data)

• No single hemp “micron standard” yet for textiles; width is commonly reported as the practical proxy for fineness. (Wilson College of Textiles)

• Cross-section shape varies; report “width (proxy for fineness)” explicitly when using optical methods such as OFDA. (SGSCorp)

• Method declarations are essential: name your optics, image processing, thresholds and sample prep. Reviews and lab pages stress this for interoperability. (MDPI)

Why choose OFDA for bast fibres (fact-based, pragmatic)

• Distribution-first: OFDA workflows naturally produce histograms and large sample counts—key for variable bast fibres. (OFDA)

• Field to lab: OFDA 2000 covers quick studies and pilot production; OFDA 4000 scales to sliver-like formats with true length distributions. (IWTO-62 is a wool method; we’re applying its principles to bast in a clearly stated, adapted workflow.) (Woolwise)

• Global support: Australia-based, serving mills, labs and producers worldwide. (OFDA)

FAQs

Is there a standard hemp “micron” test? Not at present for textiles. Many labs report width via optical image analysis and state the method; NC State, for example, lists microscopy/image analysis approaches and notes no specific hemp diameter standard in its services table. (Wilson College of Textiles)

Can OFDA measure hemp fineness? Yes—as width (a practical fineness proxy). Research has measured degummed hemp with OFDA and correlated width with residual gum. Clearly label results as “width (proxy for fineness)”. (SGSCorp)

What about length—hauteur vs true length? Hauteur/Barbe are capacitance-based trade measures from wool top testing and are not the same as true length distribution. For bast fibres, we recommend stating you report true length distribution (optical) and defining any short-fibre threshold used. (IWTO-62 defines true length for wool; we apply the concept, not the standard.) (Woolwise)

References (selection)

• Hemp measurement landscape & challenges: Reviews on hemp length and characterisation (prep challenges, method fragmentation). (MDPI)

• Lab practices: NC State Zeis Textiles Extension hemp testing table (microscopy, ISO 13322 image analysis for length/width). (Wilson College of Textiles)

• OFDA in hemp research: Optical Fibre Diameter Analyser (OFDA) used to assess hemp fibre width and relate to residual gum; note non-circular cross-section. (SGSCorp)

• True length distribution concept (wool tops/slivers; methodological analogue for bast): IWTO-62 overview; measurements on slivers/tops. (Woolwise)

• Agronomic influence on fineness via image analysis: Scanner-based image analysis linking harvest/agronomy to fineness distribution. (ScienceDirect)

• Hemp product standard (context, not fibre test): ISO 24260 (hemp fibre mats/boards). (ISO)

• OFDA4000 product capability (automation; distribution outputs). (OFDA)