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Dark & Medullated Fibre

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The Dark Fibre Testing service offered by AWTA is targeted at white-wool growers who are attempting to manage contamination from exotic sheep breeds, or who wish to monitor the contamination in lots carrying a high risk of contamination.

Two technicians visually examine four specimens, each of 5 grams, of washed and carded core sample using the Dark Fibre Detector to identify the dark and medullated fibres present. These samples are inside a sealed plastic bag, from which the air has been excluded, where they are immersed in a solvent with the same refractive index as wool. The white wool fibres become transparent but under certain lighting conditions the dark and medullated fibres become visible and can be counted. These results are issued as Test Reports and reported according to one of the following options:

Test Result

Fibre Count


0 - 10 fibres (per 10 grams)


11 - 20 fibres (per 10 grams)


>20 fibres (per 10 grams)

Growers wishing to utilise the service must request it through their wool selling broker or wool selling agent before their lots are sampled for certification for Yield, Vegetable Matter Base and Mean Fibre Diameter. 

Find out more:

Dark & Medullated Fibres - How does it workPDF

Dark & Medullated Fibres - The facts about testingPDF

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