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Alternative Uses for OFDA Technology

Brims, M. A. (1993). New OFDA developments and the use of the OFDA as a projection microscope. IWTO, Istanbul, Turkey.

            An overview to the use of special software that allows the OFDA to be used like a projection microscope.


Brims, M. A. and A. D. Peterson (1994). Measuring fibre opacity and medullation using OFDA - theory and experimental results on mohair. IWTO, Technical report 21, New Delhi, India.

Describes the optical principles used in the OFDA100 upgrade to measure fibre opacity and hence medullation of individual fibres.  The paper included graphs of fibre opacity for cashmere and mohair and a comparison of medullation determined by projection microscope and by OFDA.


Peterson, A. D. (1994). Development of the Optical Fibre Diameter Analyser to measure the fibre diameter profile of single wool fibres. Perth, West Australia, Department of Agriculture.

Describes the initial results of a software module that allows the OFDA100 to scan single fibres mounted on a frame that replaces the normal glass slide.  Fibres up to 55 mm in length may be scanned and a high resolution graph of diameter at 7 µm intervals along the fibre can be obtained.


Peterson, A. D., S. G. Gherardi and M. A. Brims (1994). "The measurement of medullation in mohair using the Optical Fibre Diameter Analyser." Proc. Aust. Soc. Anim. Prod. 20: 363.

Briefly describes work carried out to compare projection microscope and OFDA100 measurements of medullation and gare in mohair.  Results indicate that whilst medullation can be repeatably measured by OFDA, further work is required on the measurement of kemp.


Edmunds, A. R. (1995). OFDA measurements of additional fibre parameters: some preliminary results. IWTO, Technical report 19, Harrogate, UK.

Describes experimental results obtained using the OFDA100 upgrades for measuring medullation and fibre curvature.  Good correspondence was obtained between measurements of medullation on OFDA and with the projection microscope.  Fibre curvature was found to increase if the samples were aqueous-scoured prior to measurement.


Lupton, C. J., D. L. Minikheim, F. A. Pfeiffer, et al. (1995). Concurrent estimation of cashmere down yield and average fibre diameter using the Optical Fibre Diameter Analyser. 9th International Wool Textile Research Conference, 2, Biella, Italy.

Two groups of 75 and 54 cashmere samples were compared for OFDA100 estimated yield against yield determined using the Shirley Analyser, and correlation coefficients ( R²) of 0.83 and 0.72 were found.  Mean fibre diameter of down from the original histogram was found to be highly correlated with the mean fibre diameter measured on the down from the Shirley analyser process.


Peterson, A. D. and S. G. Gherardi (1995). "Measurement of cashmere yield and mean fibre diameter using the Optical Fibre Diameter Analyser (OFDA)." Australian Journal of Experimental Agriculture 36: 429-435.

110 samples were measured for yield using both the OFDA100 and the conventional Shirley Analyser methods.  The relationship between the two sets of results yielded an R² of 0.59.  Measurements of mean fibre diameter were compared between the OFDA and an FDA instrument.  It was concluded that the OFDA was capable of measuring cashmere yield and diameter to an acceptable precision.


Peterson, A. D. and S. G. Gherardi (1995). Using the Optical Fibre Diameter Analyser to measure medullation in mohair. 9th International Wool Textile Research Conference, 4, Biella, Italy.

Percentage gare, kemp, and non-medullated fibres as measured by the OFDA100 (2000 counts) were compared with measurements made with the projection microscope using 400 and 800 fibres.  There was good agreement for the percentage of medullated fibres in the range from 2 to 15% when 800 fibres were measured on the PM, but the agreement for kemp was poor.


Smuts, S., A. Schleth and L. Hunter (1995). OFDA measurement of wool fibre crimp - a preliminary report. IWTO, Special topics group, Nice, France.

25 wool tops, previously measured for staple crimp and bulk, were measured using the OFDA100 fibre curve option.  A high correlation was found between OFDA curvature and staple crimp, and between OFDA curvature and bulk.


Turpie, D. W. F. and C. H. Steenkamp (1995). Objective measurement of objectionable medullated fibres in commercial mohair tops using an Optical Fibre Diameter Analyser (OFDA): An introductory study. IWTO, Technical report 1, Harrogate, UK.

Extensive comparisons were shown between counts obtained under different opacity thresholds on the OFDA100 against visual counts of objectionable fibres in mohair.  A high correlation was found between visual and OFDA results.


Turpie, D. W. F. (1995). Report on round trial No. 1 of the working group on "Objectionable medullated fibres". IWTO, Special topics group, Nice 1995.

Reports the results of an international round trial involving 8 laboratories measuring 5 wool samples and 5 mohair samples.  Good correlation was found between visually objectionable fibres and their measurement using OFDA100.


Baxter, B. P. (1996). Preliminary investigations into the use of OFDA for estimating bulk. IWTO, Technical report 13, Capetown, South Africa.

Describes the first investigations into using OFDA diameter and curvature to estimate bulk.  A linear relationship was demonstrated between predicted bulk and values measured by the NZS 8716 bulk test method.


Baxter, B. P. (1996). Analyses of precision statistics arising from the July 1996 medullation round trial. IWTO, Technical report 2, Nice, France.

Analyses all the round trial data in order to provide comprehensive statistics on the precision of the IWTO-57 (OFDA medullation) test method.  It was found that the precision values were effectively similar for all of the assessed count-based parameters at each level of that parameter.


Brims, M. A. (1996). Measurement and calibration of opacity using OFDA. IWTO, Capetown, South Africa.

            Explains the methods used to calibrate OFDA100 instruments for opacity, and examines alternatives.


Cottle, D. J., C. D. Almeida, B. P. Baxter, et al. (1996). "Precision of OFDA fibre diameter measurements of midside wool samples." Wool Technology and Sheep Breeding 44(4): 295-302.

Study of the precision of OFDA measurements of midside fleece samples.  Reports 95% confidence limits of ± 0.6 µm for mean fibre diameter and ± 0.4 µm for standard deviation.  Intended to provide preliminary data to be used in the joint Australia - NZ standard for fleece testing.


Edmunds, A. R. and R. M. W. Sumner (1996). Further data on the use of OFDA for estimating raw wool bulk. IWTO, Technical report 7, Nice, France.

141 NZ wools from 7 breeds of sheep were measured using the NZ standard test method for bulk, NZS 8716, and for curvature and diameter using the OFDA100.  Good correlation was found between core bulk and a linear combination of radius of curvature, mean fibre diameter, and SD of diameter.


Hunter, L., S. Smuts and L. Dorfling (1996). The characterisation and measurement of objectionable medullated fibres in wool and mohair using image analysis. IWTO, Special topics group, Appendix 4, Capetown, South Africa.

Describes work at the CSIR Division of Textile Technology to measure medullation in mohair and its effects on dying.  Experimental results based on the measurement of diameter and medulla diameter ratio on Cape mohair and carpet wools were reported, together with results of assessments of objectionable fibre counts.


Lee, J. A., A. P. Maher, C. M. A. Frampton, et al. (1996). Comparison of medullation on the same fibre sites using OFDA and projection microscope. IWTO, Technical report 14, Capetown, South Africa.

Comparative measurements of medullation were made at the same sites on individual fibres using both OFDA100 and the projection microscope.  The data was used to explore several aspects of the relationship between OFDA opacity and medullation.


Turpie, D. W. F. (1996). Report on confidence limit analysis pertaining to round trial No. 1 of the working group on 'Objectionable medullated fibres'. IWTO, Special topics group, Appendix 1, Capetown, South Africa.

Using the first round trial data, reports the calculated confidence limits for OFDA100 measurement of objectionable fibres, flat fibres, total medullation, opacity, SD of opacity, mfd of medullated fibres, as well as MFD and SD of the sample.


Turpie, D. W. F. (1996). Objectionable medullated fibre in wool and mohair - Results of round trial No. 2 and comparative results obtained by projection microscope. IWTO, Technical report 5, Nice, France.

Reports the results of an international round trial based on IWTO-DTM-57 involving 8 laboratories and 80 samples of scoured wool and mohair as well as tops.  The author concludes that the OFDA100 presents a rapid, practical and cost-effective method for estimating both objectionable fibres and total medullation, which correlated at levels of 90% and 92% respectively with ASTM measurements of kemp and total medullation.


Anon. (1997). A preliminary study of fibre curvature measurement using Sirolan-Laserscan and its potential applications. Laserscan News: 3-7.

Describes the measurement of curvature using the Laserscan fibre optic discriminator, and relates the measurements to OFDA100 curvature measurements; resistance to compression results; and to the differences between measured and TEAM predicted hauteur, and to % error in evenness predicted by YarnSpec.


Brims, M. A. (1997). Along-fibre diameter and cleanliness measurement using OFDA. IWTO, Technical report 23, Boston, USA.

Introduces a new OFDA100 software upgrade that allows the instrument to measure diameter variation along approximately 0.2 mm of individual snippets.  From these measurements, the uniformity of the fibre can be determined, and the area of blobs such as residual grease can be reported as a percentage.


Edmunds, A. R. (1997). Within-laboratory precision of OFDA measurement of fibre curvature and prediction of bulk. IWTO, Technical report 21, Boston, USA.

Estimates were made of the within-laboratory precision of the values of mean fibre curvature, radius of curvature, and predicted core bulk obtained using OFDA100 measurements.  It concluded that satisfactory precision could be obtained for estimating core bulk by measuring 2 slides per sample on 'wholeslide x 1' setting.


Edmunds, A. R. (1997). "Measurement of fibre curvature: A review of work to date." Wool Technology and Sheep Breeding 45(3): 227-234.

            Reviews work carried out up to 1997 on the measurement of fibre curvature.


Greatorex, P. R., D. G. Knowles and G. V. Barker (1997). Evaluation of alternative methods for fibre curvature measurement of New Zealand Wools. IWTO, Technical report 18, Nice, France.

A strong relationship was found between fibre curvature values measured by OFDA100 and Laserscan, and an adequate relationship was found between curvature and bulk, although no attempt was made to incorporate diameter into the model.


IWTO (1997). IWTO-57: Determination of objectionable medullated fibre content of wool and mohair samples by opacity measurements using an OFDA. Ilkley, IWTO.


Lobb, J. T., K. A. Hansford, W. Humphries, et al. (1997). A preliminary study of fibre curvature measurement using Sirolan-Laserscan and its potential applications. IWTO, Technical report 8, Boston, USA.

Reports a preliminary investigation into the validity and application of fibre curvature measurements using Laserscan.  The results are compared with measurements of curvature undertaken with the OFDA100, and the authors conclude (on the basis of a correlation coefficient of 0.91) that the measurements are in "good agreement" (although the measurement units used were different).


Lupton, C. J. (1997). Further medullated fiber measurements on selected maohair samples from round trial 2. IWTO, Medullation working group Annex 1, Boston, USA.

Reports data comparing OFDA100 medullation and kemp measurements with ASTM method D2968, using 10,000 fibers in the latter.  The results show excellent correlation between the two sets of measurements, with correlation coefficients of 0.994 and 0.970 respectively for ASTM 'kemp' versus OFDA 'opacity > 94%', and ASTM 'total medullated fibres' versus OFDA 'total medullated fibres'.


Maher, A. P. (1997). OFDA measurements of opacity on medullated fibres: precision estimates from the first round trial. IWTO, Medullation working group Annex 2, Boston.

Analyses the outcome of a round trial to determine the precision of medullation measurement using the OFDA, and concludes that there is little benefit in measuring each slide more than once, or from measuring more than two slides per sample.


Wear, J. L. and B. P. Baxter (1997). Investigation into the relationship between contamination parameters measured by the OFDA and IWTO-10 measurements on commercially-scoured Australiasian wool. IWTO, technical report 4, Nice, France.

Used the OFDA "blob" parameters (along-fibre aspherities) to develop a regression relationship used to predict the residual grease measurement performed using IWTO-10.  The within-laboratory precision of the predicted residual grease was similar to that of IWTO-10, giving QC laboratories an ideal tool to monitor fibre cleanliness.


Baxter, B. P. (1998). "Preliminary results on using the OFDA to discriminate between wool, cashmere, and mohair." Wool Technology and Sheep Breeding 46(1): 24.

Using a combination of along-fibre parameters available from the OFDA100, statistical methods were compared with reference to their ability to automatically discriminate between wool, mohair and cashmere samples.  In this paper, very good success was reported in discriminating between wool and mohair, and an algorithm was developed which could be used to estimate blend proportions to within ± 10%.


Baxter, B. P. (1998). Some notes on the influence of colour on the measurement of medullation by OFDA. IWTO, Sliver group, Nice, France.

            Examined the results of medullation measurements by the OFDA when coloured fibres were present, and suggested a restrictive clause be placed in IWTO-57


Baxter, B. P. (1998). Continued investigation of the use of OFDA for fibre type differentiation. IWTO, Special topics group, Nice, France.

This paper describes continuing work on the use of multivariate analytical techniques on parameters reported by the OFDA100 instrument.  This paper deals with wool and cashmere and confirms that differentiation is feasible for these two fibres.  It was demonstrated that statistical techniques such as neural networks could be used for blend analyses, and suggested that an accuracy of ± 10% would be feasible.  It concluded, however, that more data would be required before blend analysis could be carried out to a level of precision that is likely to be required.  The techniques already outlined were, however, considered suitable for screening pure cashmere from pure wool or heavily adulterated mixes.


Lobb, J. T., W. Humphries and G. J. Higgerson (1998). Fibre curvature measurement using Sirolan Laserscan and OFDA. IWTO, Raw wool group report RWG07, Nice, France.

Describes a trial in which sampling technique (snippet length and cutting method) is investigated and shown to affect the curvature results from both Laserscan, OFDA, and a specially-designed CSIRO automated image analysis system.  Confirms that the 2 mm guillotining and 2 mm minicoring techniques produce comparable curvature relationships to other sampling regimes.  There was a linear correlation close to equivalence between the CSIRO instrument and OFDA for all sampling regimes, but especially on the longer snippets (2mm).  There was a curved relationship between the CSIRO instrument and the Laserscan raw curve measurements, and also between OFDA and Laserscan.  The relationships obtained between the 3 instruments for curvature were compared with previously-published relationships between OFDA and Laserscan.  The authors propose a theoretical relationship (IWTO Boston report 8) to convert Laserscan raw measurements to units of º/mm.


Lupton, C. J. and F. A. Pfeiffer (1998). "Measurement of medullation in wool and mohair using an Optical Fibre Diameter Analyser." Journal of Animal Science 76: 1261-1266.

Three experiments were conducted to compare OFDA100 and PM values of medullation, kemp, and total medullated fibre on wool and Angora mohair.  Whilst an initial experiment showed poor correlation between the two instruments, subsequent work using a wider range of medullation values showed r² values of 0.98, 0.93 and 0.97 respectively between the OFDA and PM values.  It was also found that increasing the total number of fibres counted in the PM work also substantially improved the correlation between values from the two instruments.  The two sets of linear regression equations, for wool and for mohair, had different coefficients, but it was concluded that the OFDA is capable of providing relatively fast, accurate and potentially less expensive estimates of medullated fibre characteristics in mohair and wool.


Maher, A. P. and J. S. Daly (1998). "The derivation of the cross-sectional area along wool fibres from the OFDA diameter measurements." Journal of the Textile Institute 89(1): 133-141.

A unique and theoretically sound method for deriving cross-sectional area along wool fibres is developed, based on OFDA diameter measurements whilst the fibre is rotated.  Diameter values are derived from an equation based on an ellipse whose parameters are the semi-major and semi-minor axes and the angle of rotation of the ellipse.  These parameters are used directly to calculate the cross-sectional area at intervals of approximately 3.2 µm along the length of fibres, to produce a profile at a resolution previously unattained in work reported in the relevant literature.  A unique 3 dimensional representation of the wool fibre was produced, demonstrating spiraling and dramatic variations in cross-sectional area along relatively short sections of the fibre.


Maher, A. P., B. D. Cassidy and J. A. Lee (1998). The measurement of medullation percent by volume of wool using an OFDA. IWTO, Technical report 19, Dresden, Germany.

Compared three methods of calculating percent of medullation by volume from the OFDA100 measurements of medullation by number, and proposed that an exponential transformation gave the best precision and accuracy for this parameter.


Peterson, A. D., A. Brims, M. A. Brims, et al. (1998). "Measuring the diameter profile of single wool fibres by using the single fibre analyser (SIFAN)." Journal of the Textile Institute 89(Part 1, No. 3): 441-448.

Describes an instrument called the Single Fibre Analyser (SIFAN) designed to measure the diameter profile of single wool fibres at very small intervals along its length.  The instrument is able to scan a 100mm long fibre at 40 µm intervals in less than 2 minutes.  The measurement error (se = 0.6 µm) is considered low in view of the relatively large variation in diameter found over relatively short lengths of fibre.  Fibre diameter-length profiles measured using SIFAN were compared with and found to be correlated closely with single fibre and 2mm snippet profiles measured with the OFDA100.


Wang, X., L. Chang and L. Wang (1998). Predicting fibre strength variation from fibre diameter variation. 2nd China International Wool Textile Conference, Xi'an, China.

Single wool fibre diameter and strength were measured on a single fibre analyser (SIFAN).  The CvD was then used to predict the Cv of single fibre strength (breaking load).  The results indicate that coefficient of variation of minimum fibre diameters can accurately predict the coefficient of variation of single fibre strength.  The relationship is not as strong if the Cv of mean single fibre diameter is used.


Wang, L. and X. Wang (1998). "Diameter and strength distributions of merino wool in early stage processing." Textile Research Journal 68(2): 87-93.

Investigation of fibre diameter and strength distributions in early stage processing.  Fibre diameter conforms to a lognormal distribution, and this conformity persists through early stage processing.  Single fibre strength also conforms to a lognormal distribution in general, but the conformity may be distorted by fibre damage in processes such as carding.  The authors propose a formula to estimate the coefficient of variation of single fibre strength from the coefficient of variation of fibre diameter.


Drieling, A., R. Baumer, J. Mussig, et al. (1999). "Testing strength, fineness and length of bast fibres." Technische Textilien.

Reports that airflow is too variable for determining the diameter of bast fibres that vary in respect of fibre type and degree of retting.  OFDA100 gives both diameter and diameter distribution data which compare favourably with other methods and also are reproducible.

Fish, V. E., T. J. Mahar and B. J. Crook (1999). "Fibre curvature morphology and measurement." Wool Technology and Sheep Breeding 47(4): 248-265.

The report discussed the definition of fibre curvature, and some of the processing and measurement factors that affect the results.  The authors indicate strong correlation between measurements of curvature using OFDA and Laserscan.  They suggest that a calibration method will be required before the measurement can be standardised.  In view of the sensitivity of the measurement to fibre condition and preparation, they caution the use of these measurements prior to agreement of test methods.  47 Refs.

Glass, M. (1999). "The diameter dependence of fibre medullation and the medullation weighting function." (in draft).

The concept of a medullation weighting function is introduced as a means of describing the variation in fibre medullation with fibre diameter.  Developed principally as an aid to model wool fibre diameter distributions containing medullated fibres, the medullation weighting function may find wider applicability in the classification of animal fibres.  Refers to data obtained with the OFDA100.

Lupton, C. J., F. A. Pfeiffer and A. R. Dooling (1999). "Prediction of cashmere style using objective fiber measurements." Sheep and Goat Research Journal 15(1): 1-4.

The authors used measurements of cashmere down yield, MFD, down and guard hair staple lengths, and average fibre curvature measurements in multiple linear regression models to predict cashmere style score.  Fibre curvature measured by OFDA was found to be the best single objectively measured trait for predicting cashmere style score.

Madeley, T. and R. Postle (1999). "Physical properties and processing of fine merino lamb's wool.  Part 3: Effects of wool fiber curvature on the handle of flannel woven from woolen spun yarn." Textile Research Journal 69(8): 576-582.

In woollen system processing, a reduction in fibre crimp/curvature results in greater sliver bulk, more even slubbing, hairier yarns, and loftier knitted fabric.  A subjective and objective evaluation of knitted and woven fabrics processed from batches combining specially selected individual fleeces illustrates how fabric handle can be engineered through the principal raw wool parameters of fibre curvature and diameter.

Bill, M. (2000). Experience with OFDA. 7th PMC Symposium.

The author describes EMS Chemie's experience with the OFDA100 for determining crimp and count on artificial fibres, and concludes that the instrument gives superior performance to methods previously used.

Brims, M. A. and H. Hornik (2000). Rapid image processing for measuring fibre characteristics. International Fibre Journal: 63-65.

            Describes how the OFDA, widely used in measuring animal fibres, can be applied to the measurement of chemical fibres.

Dorfling, L., S. Smuts and L. Hunter (2000). Measuring and characterising objectionable medullated fibres in mohair. 10th International Wool Textile Research Conference, Poster session SF-P1, Aachen, Germany.

The authors report on the distinguishing features of two groups of medullated fibres ("objectionable" and "non-objectionable") and methods of measurement, using the OFDA100, image analysis, projection microscope and medullameter.


Fish, V. E., T. J. Mahar and B. J. Crook (2000). The influence of preparation techniques on the measurement of fibre curvature. IWTO, Commercial technology forum paper CTF06, Christchurch, New Zealand.

The authors conclude that the following all have an influence on curvature results: minicored mass, repeatedly minicoring the same mass, and the state of sharpness of the minicore tubes.  Extended conditioning time was found to have no effect.

Lupton, C. J., D. F. Waldron and F. A. Pfeiffer (2000). Prickle factor in fleeces of performance-tested fine-wool rams. San Angelo, Texas, Texas Agricultural Experiment Station: 103-110.

Fibre diameter distributions were measured in 3 consecutive years using an OFDA100 on core samples of unskirted fleeces from 524 fine-wool rams completing a central performance test.  MFD, SD and CvD were also measured on britch and midside samples.  The prickle factor, SD, and CvD did not differ among years.  The authors derived a regression equation to predict prickle factor from MFD, SD and CvD, and concluded that since 92% of the variability in PF was accounted for by MFD and CvD, it was not necessary to include PF in selection index equations.


van Rensburg, B. (2000). "Fibre curvature: overview and evaluation for South African wools using OFDA and Laserscan." Wool Technology and Sheep Breeding 48(3): 233-252.

OFDA and Laserscan were used to measure fibre curvature on IH tops and South African core samples.  It was concluded that using "wholeslide x 1" and "wholeslide x 2" settings on the OFDA yielded equivalent results for both tops and core samples.  Measurements using 1000 and 2000 snippets gave equivalent results on the Laserscan for tops, but not for core samples.  There were also biases between the two instruments.  The author recommended that more work was required on the Laserscan to establish whether 2000 snippets is adequate to obtain a repeatable curvature result.

Wang, X. (2000). "Predicting the strength variation of wool from its diameter variation." Textile Research Journal 70(3): 191-194.

Derivation and evaluation of a simple statistical relationship between the coefficient of variation of fibre breaking load and that of minimum fibre diameter.  The relationship indicates that Cv breaking load is about twice CvD.  The relationship has been verified using SIFAN measurements.

Naylor, G. R. S. (2001). Report on an international round trial to establish precision data on the working group draft test method "Measuring the diameter distribution of fibre ends in sliver". IWTO, Sliver group report SG01, Shanghai, China.

Summarises the results of the round trial to measure diameter distribution both normally and on fibre ends using both OFDA100 and Laserscan.  (The results show better precision than the statistics shown in IWTO-47)

Smuts, S., L. Hunter and M. van Rensburg (2001). "The role of sheep breed and mohair style and character in the OFDA curvature vs staple crimp/wave frequency relationship." Wool Technology and Sheep Breeding 49(1): 53-61.

Studies how sheep breed and mohair style affect the OFDA100 curvature vs staple crimp or mohair wave frequency relationship.  Good correlations were found for both wool and mohair, and the authors conclude that OFDA curvature can be used as a measure of wool staple crimp or mohair wave frequency without the need to take either sheep breed or mohair style and character into consideration.


Sumner, R. M. W. and M. P. Upsdell (2001). "Factors associated with the prediction of core bulk from fibre diameter and fibre curvature of individual fleeces." Wool Technology and Sheep Breeding 49(1): 29-41.

The authors consider that it is desirable for wool growers to be able to select sheep for breeding, at minimal cost, according to the bulkiness of their wool.  The paper reports trials evaluating the effects of several farm-related factors on the prediction of core bulk from simultaneous measurements of fibre diameter and fibre curvature using an OFDA100 instrument.  Factors investigated included the effects of breed, sampling site, age of animal and the sire. The trials indicated that core bulk can be effectively predicted under field conditions.  Calculation of a universal relationship will however be dependent on the development of a standard test method for the measurement of fibre curvature.


Swan, P. G. (2001). Understanding fibre curvature. Australian Farm Journal: 67-70.

            Explains how mean curvature and curvature distribution measurement can be used by Merino stud breeders and commercial wool producers.

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