Yak and sheep’s wool: the fibres hidden behind cashmere

 

Kim-Hô Phan, Stephan Rütten, Crisan Popescu, Martin Möller

DWI – German Wool Research Institute at the University Aachen, Germany

Contact: phan@dwi.rwth-aachen.de

 

Paper presented at the 4th International Cashmere/Wool Identification Symposium in Erdos-City, 17-19th November 2008

 

1. Introduction

At the end of the 20th century, cashmere has become more popular and affordable not only for wealthy customers since China has evolved from a raw material supplier to a cloth and apparel producer and launched cashmere sweaters, shawls… for very competitive prices in the world market. The demand for cashmere has quickly increased world-wide. The current price (end of 2008) for a premium dehaired cashmere fibre quality remains at a high level of 100 USD/kg, i.e. nearly 10 times that of Merino sheep’s wool [1].

Due to its scarcity compared to other well known fibres and its high price level, other animal fibres like as sheep’s wool, camel hair, Angora rabbit hair, yak… are blended into cashmere for reducing cost, or rather for making greater profit. The fraudulent adulteration of cashmere with less expensive fibres has been causing an unfair competition for producers, traders, retailers of legitimate cashmere garments.

According to the China Wool Textile Association CWTA, the total amount of cashmere sold  in the local and international market exceeds by far those produced in China and Mongolia together (Cashmere Forum 23rd July 2007) [2]. That means, the final cashmere products (sweaters, scarves etc.) sold to the end-users are in many cases not cashmere at all or the cashmere content is substituted by a substantial amount of non-declared cheaper animal fibre. This fact can be confirmed by the number of faked label on cashmere products detected at DWI. Since 30 years the rate of detected mislabelled cashmere goods (from raw materials to end-products) at DWI has remained at a high level between 40-60% [3]. However, many of these cashmere goods bearing faked label have aroused initial suspicion during internal routine quality control by importers, department stores… because of their lack of typical tactile and visual appeal. Cautious estimates suppose that around 15-25% of garments in the market claiming to contain genuine cashmere are indeed fraudulently labelled although the retailers are often not aware of their error [4]. These are the reasons why cashmere has always been the main target of countless discussions and investigations in terms of mislabelling among the speciality fibres (cashmere, lama/alpaca, yak, mohair, camel hair, vicunia, Angora rabbit hair…). On the other side, the problem is being complicated since testing laboratories have different levels of performance in analysing cashmere garments. Many testing laboratories have namely little experience and found a substantial amount of wool in pure cashmere or classified samples containing a substantial amount of recycled wool, yak, camel hair … as pure cashmere. Furthermore, different analysis results for one and the same sample can be delivered from different well-known cashmere testing laboratories until today, especially in cases where fibre adulterants were chemically modified prior to blending with cashmere.

These obvious facts have been causing severe consequence for customers, e.g. retardation of delivery or even cancellation of orders.

After years of experiments and experience, more and more customers in China, Germany and Italy have drawn consequence in selecting DWI as the mandatory testing institution for the systematic quality control of cashmere in their goods, from raw material to woven and knitted garments, in order to be safe from incorrect labelling.

2. Fibre production

In Tab. 1, a general overview of the world production of fibres for textile use in the year 1987 and 2006 is given. In 1987 the production of natural fibre was still higher than that of man-made fibre. Roughly 20 years later, the total production of man-made fibre has surpassed by far (50%) that of natural fibres. Among the natural fibres, cotton is the most important one having an increasing production of xx%, whereas the amount of animal fibres for textile use (sheep’s wool and the speciality fibres cashmere, camel hair, yak, mohair, lama, alpaca, Angora rabbit hair, vicuna) has considerably decreased. In the next five years, the growth of man-made fibres is estimated to be again faster than that of natural fibres.

Tab. 1: World production of fibres for textile use (x 1.000 tonnes) [5, 6, 7]

 

1987

2006

%

2012 (estimated)

Natural fibres

 

 

 

30.000

   - Cotton

  18,122

  25,100

39.61

 

   - Sheep’s wool

    1,753

    1,200

1.89

 

   - Mulberry silk                

         63

        132*

0.21

 

   - Speciality fibre

         42

         31

0.05

 

Man-made fibres

 

 

 

44.500

   - Synthetics

     13,758

  34,200

53.97

 

   - Cellulosics              

    2,833

    2,700

4.26

 

 

In Tab. 2, the world production of sheep’s wool, the goat family (cashmere, cashgora, mohair) and fibres being used in blends with cashmere in the year 1987 and 2006 is listed. Within the goat family, only cashmere and mohair are produced and processed in commercial volumes.

Cashmere: During the period of 1987-2006, the cashmere production has virtually doubled to 8.000 tonnes. In some publications, the cashmere volume has been given as 15,000 tonnes instead of 8,000 tonnes. Of course the former rate is consistent with the raw material being directly gained from the cashmere goats which contains not only down fibres but also coarse hairs and other residues (greasy cashmere). After washing and dehairing, the amount would be reduced to 8,000 tonnes.

Main production countries of cashmere are China and Mongolia (around 80% of the total production). Iran, Afghanistan are the next important source for cashmere. Other countries like India, Nepal, Pakistan, Kazakhstan, Kyrgyzstan, Russia … contribute only much smaller quantities. But the animals from these countries produce comparatively coarser cashmere.

Table 2: World production of sheep’s wool and luxury fibres

 

Code

1987

[tonnes]

2006

[tonnes]

Primary producers

Sheep

WV

WO

1,753,000

1,200,000

Australia, New Zealand, South Africa, South America, China …

Camel hair

WK

    2.000

    2.000

China, Mongolia

Goat family

 

 

 

 

   - Cashmere

WS

      5,000

    8,000

China, Mongolia, Iran, Afghanistan, Middle East

   - Cashgora

WSA

       200

?

Australia, New Zealand

   - Mohair

WM

  24,000

5,000-6,000*

South Africa, Turkey, USA, Argentina, Australia, New Zealand, Lesotho

Angora rabbit hair

WA

  10,000

    8,500

China, France, Chile

Yak

WY

       200

    7,000

China, Mongolia

 

Due to large problem of overgrazing which has caused ecological devastation in China and Mongolia, China has had to kill hundred thousands of cashmere goats in the last ten years. The cashmere production is therefore expected to stagnate in the two main producing countries and insignificantly increase in other regions in the future.

Cross-breeding programmes of cashmere goat with Pridon bock from Russia for increasing the fibre yield and for improving the fibre colour to off-white shade have led to coarser cashmere quality in certain cashmere strains (or breeds ???) in Mongolia and Central Asian countries and even in China.

Yak fibre: Yak is a domesticated animal (Bos grunniens) living in countries in East Asia which has been grown for meat, milk, hide and draught animal since centuries. The main growing countries are China and Mongolia. The double-coated fleece of yaks consists of, similar to cashmere goats, long coarse outer hair and soft under down which sheds annually in spring and is normally shorn or combed.

Until the beginning of the 1980’s, yak fibre was considered as a by-product in breeding the animals and was seldom mentioned as a fibre of textile relevance. Since centuries, yak fibre – together with coarser yak hair - have been used by nomads for making ropes and other simple insulating devices, blankets, mats, tents. But since Chinese textile companies are able to separate the yak fine down fibres from the outer coat hair, the fibre has continuously gained higher value and has been adopted as a speciality fibre like cashmere, camel hair.

On the internet, yak down fibre has been offered by many traders from 1 to 300 metric tonnes each, not only in China but also in Great Britain and elsewhere. In Mongolia, price for yak fibre has increased by 5-7 times and vary between 20.000 – 35.000 Tugriks (13 – 23 Euro/kg) in 2007. The price has never been so high [8].

Since most yak animals live in China, most studies and publications have been done and written in Chinese. The papers in Chinese were compiled in a work by Prof. Cai Li “China Yak” and published in 1992. The work has been translated into English with the title “THE YAK” and published by the Regional Office for Asia and the Pacific of the FAO of the United Nations. Most publications concern the breeding of yak, its influence in the life …the production of meat, milk and hide .

Dates about yak fibre is rarely found in the literature in Europe and the USA. According to the book “THE YAK”,  the total yak population is estimated to a number of 14.2 million, of which 13.3 in Chinese territories, about 0.6 million in Mongolia and the rest in other countries ( Nepal, Bhutan, Central Asian countries) at the present time. Their numbers are said to increase in China  [9].

Estimates of the volume of yak fine fibre vary considerably. A specially selected “fibre line” of Jiulong yak can yield up to 10-12 kg fine fibre (without coarse hair) per head, this is ten-fold the yield of most ordinary yak (1-1.2 kg/head) [Cai Li et al. (1980a)]. Based on a low yield of 0.5 kg fine fibre per animal, the total volume of yak would be around 7,100 tonnes. A publication in the year 2000 reported about an annual production of 7,060 tonnes of fine yak fibres, which is higher than the cashmere production in China [10]. 

Since around ten years, a new term has slowly ingrained in the market: yak cashmere. The term has been used in China and Outer Mongolia to intentionally upgrade yak fibre which is very well dehaired and supposedly has similar characteristics compared to those of cashmere. Even in scientific publications, the term yak cashmere has been used to increase the desirability of the fibre. But sale of textile apparels made of pure yak fibre has also been newly promoted and sold in the Western countries.

Sheep’s wool: fine Merino wool up to 20 µm has been identified as the most used fibre for mixing into cashmere, legally or illegally. In order to “masquerade” fine wool fibre as cashmere, attempts have been made by partial eroding wool fibres by chemical means e.g. chlorination, steaming etc.

In the Qinghe province in China, there is special type of sheep bearing double-coated fleece similar to cashmere goat. Prior to use, the fleece also has to be dehaired. The fine down fibres are well in the cashmere range and officially known as Chinese native fine sheep wool or even sheep cashmere. Similar to yak cashmere, the term sheep cashmere has been used to intentionally, but not legally upgrade this special type of wool. Qinghe wool or “Yingtse” wool are other terminologies for this wool type known at DWI since the mid-1980s.

Another type of modified wool, OPTIM wool, has also been found in supposedly pure cashmere. Optim wool is made according to a special procedure by stretching, twisting and then chemically setting Merino wool sliver. After stretching, the distorted fibre becomes thinner (by 3 – 3.5 µm) and longer, ditto the cuticle scales. Optim wool has been launched in the market and already identified at DWI as a cashmere substitute.  In many cases the scale frequency can be 5-6/100 µm fibre length or even lower, quite comparable with that of cashmere. The height of most scales is reduced to less than 0.4 µm. The misshaped whole form of the fibre, the irregular scale structure and some remained high cuticle scale edges are features which help to identify Optim wool among cashmere fibres.

Recycled wool has been often found as cashmere adulterant in woven fabrics for men’s and women’s outwear coats. The mechanical rupture process causes typical damage which is reflected in fibre fibrillation, partial erosion of fibre surface. These prominent features, together with remained intact cuticle scales, enable a clear-cut differentiation between recycled wool and cashmere.

Since around two years, we remark an increased use of lambswool and superfine wool as cashmere substitute. The latter has individual diameter of 8-12 µm and coronal scale shape and thus can be easily mistaken for cashmere. But high cuticle scale edges and high scale frequency reveal their true identity. Lambswool fibres are also very fine with thin cuticle scale edge, but the length of individual cuticles is quite irregular with alternate long and short cells, whereas the distance between scales of cashmere fibre is as a rule quite regular.

3. Fibre identification and differentiation by means of scanning electron microscopy

Since the keratin fibres for textile use are very similar in chemical structure, the differentiation of cashmere from other speciality fibres by chemical methods is not possible as it is common for synthetic and cellulosic fibres.

Up to now the commercial analysis of cashmere can be performed by means of three methods: the light microscopic (LM), the scanning electron microscopic (SEM) method and the DNA technique.

All three techniques have been practised at DWI for the analysis of keratin fibres, whereby both the latter techniques were introduced at DWI for the first time in the world in the year 1982 (SEM technique) [11] and in 1988 (DNA technique) [12]. 

In the mid-1990’s the DNA technique was withdrawn from the customer service of DWI  because many problems occurred by the analysis of treated/modified cashmere in garments. Textile processes can wash the DNA molecules out of the fibre or modify their chemical structure, so that they can not be clearly isolated and detected anymore. Already after a mild washing process, the amount of DNA within cashmere fibre decreases from approx. 74 nanogramm per g fibre to an amount of only 4ng DNA/g fibre [13]. Even with the aid of the PCR technique, the cashmere analysis results by using the DNA technique remain very controversial. At the IWTO meeting in Beijing in 2008, a discussion has been started in order to propose this technique as a Draft Test Method (DTM) of the IWTO. But the DTM would be applied just for raw materials and not for processed fibres at all.

Till this day only the microscopic techniques LM and SEM are recognised in standard test methods for cashmere analysis [14, 15, 16]. Despite the standardisation, these techniques require very experienced operators, as the accuracy of the analysis depends largely upon the ability of the individual specialists in identifying the particular fibre. Both standards have clearly underlined the fibre specialists’ practical knowledge. The different levels of the operators’ experience using either the LM or the SEM are therefore the reason for the discrepancy of cashmere analysis results, even from the well-known testing laboratories.

The existence of objective “topographic fingerprints” from each generic fibre by means of SEM is typical enough to reveal its true identity and is of paramount importance for keratin fibre analysis. It is astonishing that a fibre snippet of 0.4 mm length exhibits on its surface enough information about its generic origin, so that the fibre identification and differentiation can be done after a long-term and systematic studies of the individual fibre types and practice.

In my booklet of 1991 [17] I prognosticated that the textile testing laboratories would be forced to upgrade their equipment with a SEM in order to meet the customers’ high demand. In fact, approx. 10 test labs around the world have acquired a SEM since then. But many of these labs doesn’t appear yet on the CCMI list of laboratories which must have facilities and personnel capable of identifying and distinguishing fine animal hair fibers [3]. Even one lab using the SEM for cashmere analysis was withdrawn from the list after having changed the fibre analyst. That means, beside a good tool, years of experience of the operator is inevitable for doing an accurate cashmere analysis.

4. Literature

1)  Schneider Group, Market indicator, http://www.gschneider.com/indicators/index.php

2)  China Wool Textile Association, http://www.chinacashmere.org

3)  Phan Kim-Ho: “Differentiation and analysis of speciality fibres”, Report at the Meeting of the DTB (Dialogue Textile & Garment), Munich 25th Sept. 2007

4)  CCMI, http://www.cashmere.org/cm/index.php

5)  Anon., Chemiefasern/Textilind. 9 (1988)

6)  http://www.textile-info.com/1161.htm

7)  Silk production, http://www.crbtrader.com/fund/articles/silk.asp

8)  Badmaanyambuu Ranjil, Cashmere & Wool Testing Centre at the Mongolian Textile Institute, ITDS, MUST, personal communication (January 2008)

9)  Wiener Gerald, Han Jianlin, Long Ruijun “The Yak”, FAO of the UN, Reg. Office Asia & Pacific, AP Pub. 2003/06, 2nd Ed. (2006) 1-460    

10) Yan Kelu, Höcker Hartwig, Schäfer Karola:“ Handle of Bleached Knitted Fabric Made from Fine Yak Hair”, Text. Res. J. 70 (2000) 734-738.

11) Kusch P., Arns W. „Rasterelektronenmikroskopische Unterscheidung von Schafwolle und Ziegenhaar (z.B. Mohair), Melliand Textilb. 64, 427 (1983)

12) Berndt H. et al.: „Eindeutige Provenienzanalyse von Wolle und feinen Tierhaaren mit Hilfe der Erbsubstanz DNS “,  Textilveredlung 23, 304-307 (1988)

13) Hamlyn Paul F: “Identification of Animal Fibres using DNA Profiling Techniques”, Paper presented at the World Textile Congress on Natural and Natural-Polymer Fibres, University of Huddersfield, UK (1997)

14) ASTM D629 “Test Methods for Quantitative Analysis of Textiles”, American Society for Testing  and Materials, Part 33 ASTM Philadelphia (1995)

15) AATCC Test Method 20, “Fiber Analysis: Qualitative” and Test Method 20A “Fiber Analysis: Quantitative”, American Association of Textile Chemists and Colorists,

16) IWTO, TM-58: “Quantitative Analysis of Blends of  Wool with Speciality Fibres by Scanning Electron Microscopy” (2000)

17) Phan Kim-Ho: “Electron Microscopy and the Characterization of Keratin Fibres” Comett Eurotex, Guiamarães, Portugal (1991) 1-72