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Preparation and Dark Fibre Contamination
Foulds R.A.,Seminar Proceedings: Clip Preparation Research, CSIRO Division of Textile Physics & Australian Wool Corporation (Research & Development), April 1983. |
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Provides the background to the dark fibre problem as it impinges on clip preparation and illustrates the method developed to detect and classify dark fibres in tops. The results obtained are used to demonstrate to what extent two types of dark fibres, originating on the sheep, contribute to the clip preparation story. |
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Dark Fibre Contamination in Wool - Its Prediction and Ramifications
Foulds R.A., Seminar Proceedings: Technical Feasibility of Sale by Description, CSIRO Division of Textile Physics, July 1988 |
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An obvious question is: Why not sample and test greasy wool for dark fibre contamination, thereby, avoiding claims on buyers and topmakers for unacceptable products.
Unfortunately, we can't have a pre-sale test. Topmakers have set maximum limits for dark fibre contamination which are very low, typically one hundred dark fibres per kilogram of top. This can originate from less than five grams of dark fibres per bale of wool, which is a level of contamination much too low to permit any realistic sampling and testing to be carried out. For example, just to find out if there is any dark fibre present would require sampling more than a hundred kilos of greasy wool from each sale lot.
This paper considers an alternative approach, based on an objective risk level rather than an objective test on the greasy wool. |
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Dark Fibre Risk and Prediction
Burbidge A. & McInnes C.B., Seminar Proceedings: Specification of Australian Wool and Its Implications for Marketing and Processing, CSIRO Division of Wool Technology & the International Wool Secretariat, November 1994 |
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The provision of a measurement of dark fibre content that can be used as a basis for the trading of greasy wool is not practicable. The main limitation is that only a minute amount of urine stained or pigmented wool in a consignment is sufficient to exceed the topmakers' limit, particularly for light coloured end uses.
Research has shown that the major source of dark fibre contamination in Australian adult merino wools is from urine stained fibres, with pigmented fibres being of secondary importance. On this basis a Dark Fibre Risk Scheme has been devised, which as a predictive method gives an estimate of the risk from urine stained or pigmented fibre contamination in a sale lot. It uses information which is provided on the Clip Report at shearing time.
This paper is concerned with the research leading to the identification of the sources of these contaminants and with developing a method of predicting the probable level of contamination in individual sale lots and consignments from these sources. |
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Exotic Sheep Breeds in Australia - A status report
AWTA Ltd, February 2000 |
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This report summarises the current status of concerns with regard to contamination of the merino clip from coloured and/or medullated fibres from imported exotic sheep and their crosses with merino ewes. It draws on published information from a number of sources. |
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Dark Fibre Control in Sheep and Wool
PIRSA/SARDI, July 2000 |
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Quality assurance schedules for production and preparation of premium quality wool generally recognise dark fibre as a serious fault that is not currently measured in greasy wool presale. Dark fibres at concentrations of less than 1 to a few parts per million can be a problem. An often quoted upper tolerance for Merino wool to be used for critical end-uses is 100 dark fibres per clean kg.
Identification of dark fibres in greasy wool presale is unlikely for dispersed or isolated contaminants of low concentration and the largest costs to the wool industry occur after value adding by processors when the fault is first recognised (Figure 1). Dark fibres limit flexibility of end-use, or when identified in late stage processing may require fabric or garment mending, resulting in financial loss for processors who need to allow for such ‘surprises’ in the prices paid for greasy wool.
Reliance is placed on sheep breeding and management and clip preparation and wool marketing requirements to minimise dark fibre risks. |
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Wool Contamination: pigmented and heavily medullated fibres
PIRSA/SARDI, December 2000 |
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This fact sheet provides information for wool production and wool classing on farms, groups involved in quality assurance and agencies overseeing these standards, wool marketing and exporting and wool processing. Knowledge about contamination arising from direct transfer between white sheep and coloured sheep or partly coloured sheep is reviewed. Increased interest in meat sheep breeds that present opportunities for transfer of pigmented and medullated fibre to wool sheep encourage the need for greater awareness of these risks. |
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Detection of Dark Fibre Contamination of Merino Wool
AWTA Ltd, July 2001 |
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Two laboratories testing replicate samples have investigated the Detection of Dark Fibre Contamination in core samples from commercial sale lots of merino ewe fleece wool after the ewes have been in contact with Damara Rams and Damara crossbred lambs. |
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The detection of pigmented and medullated fibre in core samples of commercial sale lots from Merino ewes mated to Damara fat tail rams
M.R. Fleet, T.J. Mahar and S.I. Denney, Report CTF 02, Commercial Technology Forum, Nice Meeting, November 2001 |
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A trial incorporating the testing of commercial core samples has provided further evidence of wool contamination arising from crossbreeding Merinos with Damara fat tail rams. The trial has also highlighted limitations of the CSIRO Dark Fibre Detector for this purpose in terms of both its subjectivity and the operator time required for a test. |
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Fibre Medullation, Marketing & Management
Sue Hatcher, NSW Agriculture, 2002 |
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There are vast differences between the ‘exotic’ sheep breeds currently run in Australia with respect to their fleece structure, fibre type composition and characteristics such as fleece shedding, pigmentation and medullation. This leads to different end uses for the fleeces from these breeds and different potential to impact upon the Australian wool clip. A greater understanding of the biology of these exotic breeds and the consequences on the fleece of crossing with the Merino is required in order to develop improved management strategies to minimise the risk of pigmented and medullated fibres contaminating Merino fleeces. Furthermore an investigation into the persistence of various animal contaminant fibres in both the worsted and woollen processing systems and the commercial development of a novel pre-sale test for quantifying dark fibres in sale lots are important. Comprehensive work in these two areas will provide a clear indication to the processing industry of the incidence and relative importance of animal fibre contaminants in the Australian wool clip. |
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Merino Crossbreeding and Objectionable Sheep Fibres: the Problem and Potential Solution
M.R. Fleet, T. J. Mahar & J.A. Turk, Paper 41, Wool Industry Science & Technology Conference, October 2002, Hamilton, Victoria, Australia |
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The presence of trace amounts of pigmented, or white kemp, fibre in otherwise white wool restricts the flexibility of end-use for the wool. Increased crossbreeding in Australia, especially the minority involving coloured or kempy breeds, has produced concerns and uncertainty about occurrence of affected wool lots. It is important for the buyer to be aware of the existence of these objectionable fibres in wool lots. AWEX has changed clip preparation standards by instigating a new bale brand qualifier ("Y" suffix) in order to reduce uncertainty in the market concerning pigmented and kemp fibre contamination. Increase in the quantities of wool appraised for the auction market as containing pigmented or kemp fibre are shown together with estimates of the penalties applying for Merino fleece wools containing pigmented fibre. Gaps remain in information concerning the range of on-farm situations where the “Y” description is warranted. Research is currently being directed at both filling these gaps in information and at the provision of a practical and reliable presale test for detection of sheep fibre contaminants that are widely dispersed through the wool lot. |
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Tackling the Dark Fibre Threat to Australian Wool
AWTA Ltd Press Release R001-2003, February 2003 |
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March 2003 sees an important breakthrough in the quest to maintain Australia's reputation for clean, white wool. For the first time, wool growers will have access to a test that screens for possible contamination of merino wool sale lots by dark and/or medullated fibres originating from contact with exotic sheep breeds. |
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Action on Dark Fibre Testing
News,AWTA Newsletter, February 2003 |
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On the 13th November 2002, AWTA Ltd announced to a seminar organised by the Federation of Australian Wool Organisations (FAWO) that it was planning to introduce a screening test for contamination of merino wool with fibres derived from contact with exotic sheep breeds. This service will be introduced in March 2003 and will be based on the CSIRO Dark Fibre Detector.
Research initiated by the South Australian Agricultural Research & Development Institute (SARDI) under the leadership of Malcolm Fleet, and collaborative research involving AWTA Ltd and SARDI, demonstrated that the presale coretest sample could be used to detect contamination of merino wool arising from contact of merino ewes with exotic rams, or contact between merino ewes and their lambs produced by matings with exotic rams. |
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Dark Fibre Risk Prediction
Features, AWTA Ltd Newsletter, February 2003 |
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The provision of a measurement of dark fibre content that can be used as a basis for the trading of greasy wool is not practicable in every instance. The main limitation is that only a minute amount of urine stained or pigmented wool in a consignment is sufficient to exceed the topmakers' limit, particularly for light coloured end uses, and it is usually not distributed uniformly hence presenting a sampling problem.
The major source of dark fibre contamination in Australian adult merino wools is from urine stained fibres, with pigmented fibres being of secondary importance. On this basis CSIRO devised a Dark Fibre Risk Scheme (DFRS), which as a predictive method gives an estimate of the risk from urine stained or pigmented fibre contamination in a sale lot. It uses information, which can be provided on the Clip Report at shearing time. |
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Is it time to re-visit Dark Fibre Risk Analysis
Opinion, AWTA Ltd Newsletter, February 2003 |
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Given the limitations of testing for contamination by dark and medullated fibres the wool industry requires a more holistic approach. Ideally this will incorporate:
- on-farm management systems to minimise the risk of contamination from any source;
- systems for quantifying the level of risk of contamination given that the appropriate management system is followed;
- a low cost presale test for potential contamination arising from contact with exotic sheep;
- technology to quantify contamination of tops; and
- technology to remove any contamination from yarns.
Fortunately much of what is required is already in place, able to be put in place relatively quickly, or made available after some development effort.
This article also includes a comprehensive bibliography to other documentation that is not available in electronic form. |
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Dark and Medullated Fibres in Merino Wool - the Facts about Testing
(original version) AWTA Ltd, March 2003 |
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The Dark Fibre Testing service offered by AWTA Ltd in March 2003 was targeted at growers who are attempting to manage contamination from exotic sheep breeds. It is not a catch-all test. It is labour intensive and slow, and therefore expensive ($150 per test). |
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Protecting the Reputation of Australia’s White Merino Wool - Dark & Medullated Fibre Testing
AWTA Ltd, March 2003 |
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Research to develop improved technology has succeeded and AWTA Ltd implemented a new service based on this techology on 1st July 2004. The new test still utilises the Dark Fibre Detector but is able to handle much larger samples due to an improved sample preparation and presentation system. |
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Managing the Risk of Dark and/or Medullated Fibre Contamination,
Literature Review prepared by Kerry Hansford for AUSTRALIAN WOOL INNOVATION PROJECT - EC573, August 2003. |
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The Dark Fibre Risk project was initiated in response to on-going concern by members of the FAWO over contamination of the Australian wool clip by dark and/or medullated fibres. Funding was sought from and provided by AWI as one of its initiatives to address the contamination issue. It is anticipated that the project outcomes will be useful in addressing concerns within the industry relating to the degree to which the Australian Merino clip is contaminated, thereby protecting its high standing. This paper provides a comprehensive review of this subject. |
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The Development of a Quantified Risk Factor for the Presence of Dark and/or Medullated Fibres in Australian Merino Wool,
K.A. Hansford and Australian Wool Industry Working Group, Report RWG07, Raw Wool Group, IWTO Dubrovnik Meeting, November 2003. |
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The Federation of Australian Wool Organisations, with funding from Australian Wool Innovation, has initiated a project aimed at the introduction of a voluntary vendor (woolgrower) declaration for the risk of dark and/or medullated fibre contamination. To oversee the project and ensure its industry focus, a Working Group comprising representatives of all industry sectors was formed.
The project was founded on previous research by CSIRO which developed a prediction scheme for urine-stained and/or isolated pigmented fibre. This CSIRO Dark Fibre Risk Scheme, which was validated by processing trials, calculated the “Risk” that a particular sale lot would meet the requirements of the white/pastel trade.
This paper reports on the development of a Dark and Medullated Fibre Risk (DMFR). The scheme is primarily based CSIRO’s Dark Fibre Risk Tree with additional information included on the contamination risk posed by contact with exotic breeds. The results of validation trials, conducted to provide a basis for any refinement to the scheme and to provide a sampling regime for possible future random testing, are presented. |
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Update of Progress in Dark & Medullated Fibre Risk Project December 2003,
P. J. Morgan, FAWO-03-211, 24th December 2003. |
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In Dubrovnik, Croatia in December 2003, the International Wool Textile Organisation (IWTO) approved a recommendation from the Federation of Australian Wool Organisations (FAWO) that a Dark and/or Medullated Fibre Risk (DMFR) scheme for Australian Merino wool be recognised in its Core Test Regulations from 1 July 2004. This allows inclusion of the Risk Level on AWTA Ltd Core Test Certificates. AWEX has been approached to facilitate inclusion in sale catalogues.IWTO recognition opens the door for the DMFR scheme to be introduced for use by Australian Merino woolgrowers in July 2004. It is anticipated that the DMFR scheme will be useful in countering alarm about the degree to which the Australian Merino clip is contaminated, thereby protecting its high standing. |
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Dark & Medulated Fibres, why are these Fibres a Concern for a Spinner at the Example of Südwolle?
Götz Giebel, Südwolle GmbH & Co. KG, Growers, Traders & Ealrly Processors Committee, IWTO, Evian Congress, May 2004 |
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This paper provides a processor's perspective of dark fibre contamination. |
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Protecting the Reputation of Australian Merino Wool
A presentation on behalf of FAWO by the Dark & Medullated Fibre Working Group, Growers, Traders & Early Processors Committee, IWTO, Evian Congress, May 2004. |
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This is a PDF version of a presentation made by FAWO to inform IWTO of the progress in implementing a Dark & Medullated Fibre Risk Scheme in Australia. |
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The Definitions of Medullation Threshold Values used by Different Testing Methods to Define an Objectionable Medullated Fibre in Merino Wool
Anjalika Balasingam, January 2005 |
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There is no objective definition of a contaminant medullated wool fibre that can be substantiated by published trials. The American Society of Testing Materials (ASTM) has published a definition in ASTM-D 2968-89 that uses the ratio of medulla to fibre diameter to define contaminant medullation. But we have been unable to locate references to a trial or trials that substantiate this value.
Hunter et al. (1996) reported a trial in which experienced mill staff visually detected objectionable medullated fibres of samples in air. The medulla to fibre diameter ratios of the detected fibres ranged from 0% to 90%, indicating that, either the detection method was unreliable or that the medulla to fibre diameter ratio is an inappropriate parameter to define objectionable medullation. However, when testing mohair in benzyl alcohol, Smuts and Hunter (1983) appeared to support the ASTM definition, although the ratio they found was 0.55 compared to 0.60 for ASTM-D 2968-89. OFDA technology has a definition of objectionable medullated fibres based on fibre opacity and diameter, but this definition is not applicable to bulk presale core testing.
Other techniques for medullation measurement such as projection microscope (pm) and the WRONZ Medullameter use the ASTM definition to directly (pm) or indirectly (Medullameter) to specify a threshold level of medullation for contamination.,
Prepared as part of Australian Wool Innovation funded project EC651. |
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