MOHAIR KNOWLEDGE AND INFORMATION DATA BASE
L. HUNTER PhD CText FTI
Mohair Knowledge and Information Data Base
L. Hunter PhD CText FTI
- Introduction to Mohair and its Special Characteristics
- Mohair Production
- Greasy Mohair Quality Characteristics
- Objective measurement
- Mohair Fibre Physical and Related Properties
- Fibre diameter (fineness)
- Fibre length
- Fibre tensile properties
- Fibre stiffness
- Fibre surface structure
- Fibre friction
- Fibre moisture related properties
- Medullation and kemp
- Mohair, Morphological, Chemical and Related Structures and Properties
- Morphological structure and related properties
- Chemical composition and structure
- Mohair flame resistance
- Mohair Processing
- Topmaking and spinning
- Effect of fibre properties on topmaking performance
- Worsted spinning performance
- Woollen processing system
- Fancy (novelty) yarns
- Knitting and Weaving Mohair
- Dyeing and Finishing Mohair
- Mohair Fabric Properties
- Comfort related properties
- Wrinkle resistance
- Drape and stiffness
- Wear performance and durability
- Mohair Fibre Identification
- Mohair Applications
- Further Reading
Mohair Knowledge and Information Data Base
This document summarises the latest technical and scientific knowledge and information on mohair, with a specific emphasis, where appropriate, on South African mohair (Cape Mohair), more detailed information being available elsewhere [1-3].
- Introduction to Mohair and its Special Characteristics
Mohair, produced by the Angora goat, is sometimes referred to as ‘The Diamond Fibre’. It
belongs to the group of fibres referred to as speciality or luxury animal fibres (Fig 1), and is one of the most ancient fibres known to man. Mohair, derived from the Arabic word Makhayar (Mukhayar or Mukhaya), is the fleece of the single coated Angora goat, Capra hircus aegagrus (Fig. 2), named after the Turkish province of Ankara (Angora or Ancyra). The Angora is thought to have originated in the Asian Himalayas (Asia Minor) or Highlands of Tibet, from where it spread to the Middle East, eventually finding a new home on the Turkish plains. The birth of the mohair industry took place in Ankara, Turkey, which was also the first country to supply mohair as a raw material. The first Angora goats to leave Turkey went to South Africa in 1838.
Figure 1: Luxury Animal Fibres
Figure 2: Angora goats (Source: Mohair South Africa)
The Angora goat is regarded as unique amongst goats, in that it is essentially single coated, with the fibres from the primary and secondary follicles not differing very widely, and it does not moult (i.e. shed its fibres annually), its fibres growing continuously throughout the year. For centuries, mohair has been regarded as one of the most luxurious and best quality fibres available to man. It is generally a long, straight (uncrimped but often wavy or curly), smooth and naturally lustrous fibre, the predominant natural colour of mohair being white. Mohair is characterised by, and renowned for, its outstanding lustre, smoothness, durability (hard wearing), elasticity, resilience, resistance to soiling, soil shedding, setting, strength, abrasion resistance, comfort, and moisture management (including moisture absorption), as well for its pleasing handle, and relatively low flammability, felting and pilling. It can be dyed to deep, brilliant and fast colours, It is a long life fibre, but will biodegrade in soil, with life-cycle benefits.
Mohair has proved extremely popular in many applications, notably knitwear, blankets, furnishings, upholstery, curtains, carpets and suitings, Its outstanding properties, such as resilience and durability (hard wearing), make it particularly suitable for household textiles, such as upholstery fabrics, curtains and carpets, it being considered one of the most durable fibres, particularly natural fibres. Nevertheless, because of its coarseness relative to most other luxury animal fibres, it has some limitations in certain ‘close to the skin’ apparel applications, although using long brushed surface fibres can mostly reduce, or even overcome, these limitations.
- Mohair Production
Today, mohair is largely produced in South Africa (which presently accounts for over 50% of global production), South African mohair (Cape Mohair), being regarded as the finest and best quality in the world. The United States of America (Texas), Turkey, Argentina, Lesotho, Australia and New Zealand are other producers of mohair.
Angora goats tend to thrive in areas of low rainfall and humidity, and can survive extreme temperatures, but are sensitive to cold after shearing, particularly a combination of cold, wind and/or rain. Angora goats can thrive on widely different types of pasture, grazing from about 30cm to 1.6m above ground level, and are very efficient in converting feed into fibre. Mohair grows approximately 25mm in length per month (i.e. ≈ 300mm per year), irrespective of age, and Angora goats are generally shorn six-monthly in South Africa, the United States of America and Argentina, and annually in Turkey (in May) and Lesotho. Greasy mohair is generally classified according to the age of the goats and when they are shorn, together with the fibre fineness (diameter).
In South Africa, the first shearing takes place in January/February, around six months after birth, and the second shearing, six months later, in July/August The mohair obtained from the first two shearings (i.e. at 6 and 12 months) is generally classified as Summer Kids and Winter Kids, respectively, that obtained from the third (and also sometimes from the fourth) shearing (i.e. at 18 months and sometimes at 24 months) is classified as Young Goats and after that (i.e. from the fourth or fifth shearing, i.e. from the age of 24 or 30 months) the hair is classified as Adults. The goats generally produce more fibre in the summer than in the winter.
Generally, mohair from Kids is finer than 29μm (varying from about 20 to 29μm), that from Young Goats finer than 34μm (varying from about 27 to 34μm) and that from Adults generally coarser than 30μm (ranging from about 30 to 40μm). In general, the best grades of mohair are from the first shearing Kids under six months old (e.g. Super Summer Kids). Young goats and Adult goats produce about 2 to 2.5kg of greasy mohair every 6 months, rams generally producing considerably more and coarser hair than ewes. In the case of Kids, the fleece barely weighs 1kg at the first shearing and is generally less than 2kg at the age of one year (i.e. at the second shearing).
Breeding (i.e. genetics) and the age of the goat are the main factors determining the quantity and quality of mohair produced.. Kids have a birth coat of fibres that grow mainly from the primary follicles, those being the follicles which primarily produce kemp and medullated fibres. From about three to six months the goats shed their birth coat (‘mother hair’), as the fibres grow increasingly from the secondary follicles which produce the finer and unmedullated hairs, the Secondary to Primary follicle ratio varying from about 6 to 12, being about 10 for well-bred goats. Fibre production and mean fibre diameter increase from birth, fleece weight reaching a maximum at an age of between approximately three and four years, and the fibre diameter a maximum at approximately five years (Fig. 3), the mohair fibres being finer towards their tips, due to the fact that the fibres become coarser as the goat ages. Fibres from the neck and britch areas of the goat tend to be coarser than those from the other parts of the body. Increased nutrition generally increases fibre diameter and fleece mass, while style and character are affected differently by nutrition.
Figure 3: The effect of age on fleece and fibre characteristics in the Angora goat
(Source: J.M. Van Der Westhuysen, D. Wentzel and M.C. Grobler, 1985, Wool Rec., 144(3493), 35, quoting Shelton, 1961)
- Greasy Mohair Quality Characteristics
In practice, the quality of greasy mohair is described as a combination of style and character, freedom from kemp, lustre, handle, yolk and uniformity of length and fineness, the presence of kemp (or objectionable medullated fibres) being one of the most undesirable quality characteristic of mohair. Handle is largely determined by fineness, although a soft natural yolk and oleaginous dip can also improve softness of handle. Mohair quality characteristics of economic importance are fineness (fibre diameter), length, style and character, contamination (kemp, coloured fibres and vegetable matter), and clean yield, lustre and uniformity in general. Fibre diameter is particularly important, as is the presence and level of kemp, with length having a smaller, though still important, effect on price and processing.
The fleece of the Angora goat, when shorn, contains natural and applied impurities; typically a total of 10 to 15% of non-fibre being present. The sweat or suint, the water soluble component, and grease (wax or surface lipids) combined are termed yolk. The grease (wax, called lanolin when purified) is secreted by the sebaceous glands and the sweat (suint) by the sudoriferous glands. Other natural impurities contained in mohair include sand and dust (i.e. inorganic matter), vegetable matter (e.g. burr, grass, seed) and moisture. Applied impurities include branding fluids and dipping compounds. Generally, mohair contains considerably less grease than wool (4 to 6% on average, compared with an average of about 15% for Merino wool). Its wax is also more oxidised than that of wool, making it more difficult to remove during scouring. Mohair from Kids and Young Goats contains more grease than that from Adults, with the grease content higher in winter than in summer, the average grease content being 4.5% for summer hair and 5.8% for the winter hair, with a melting point of 39ºC, and also higher towards the root (e.g. tip = 2.0%, middle = 4.6% and root = 6.0%).
Some typical chemical constants for mohair grease are given in Table 1.
Table 1: Typical Chemical Constants for Mohair Grease
Wax (grease) content of fleece (%)
Saponification value (mg KOH/g)
Unsaponifiable fraction (%)
125 – 135
Mohair, by virtue of its open fleece structure on the goat, particularly that of Adult goats, is more exposed to weathering than wool, the tips of the mohair fibres covering the back of the animal being more prone to damage by sunlight or weathering, especially during the summer months. This damage has an influence on the dyeing properties of the affected fibre part, as well as on the fibre strength.
Clean yield (i.e. the percentage of actual fibre plus commercially allowed moisture content in raw mohair) varies between about 80 and 90% in most fleece classes, but may be as low as 60% in some outsorts, such as lox (locks), the remaining portion being made up of grease, dirt, dust and sweat. Mohair base (i.e. the amount of clean dry fibre, free from all impurities, expressed as a percentage of the greasy fibre mass) is converted into the International Wool Textile Organisation (IWTO) scoured yield. This relates the tested yield to normal commercial yields for scoured greasy mohair. This yield is calculated from the mohair base to include all vegetable matter, standard residuals of grease and dirt, which would normally be retained in commercial scouring, and allows for a moisture regain of 17%, which means that yields of over 100% are theoretically possible.
Some average or typical values and ranges of various mohair properties are given in Table 2.
Table 2: Some Average or Typical Values and Ranges of Various Mohair Properties
Fibre Density (g/cm3)
Staple length (mm)
Curls per 10cm (wave frequency)
Ash content (%)
pH of suint
Mohair Base (%)
Scoured/Clean yield (%)
Alkali solubility (%) **
Acid solubility (%) ***
Urea bisulphite solubility (%)
Swelling in water (%)
Regain at 65% RH (%)
Water pick up (absorption) (%)
Cuticle scale height (μm)
Cuticle scale frequency
(per 100 μm)
1.27 – 1.31
20 – 40
20 – 33
80 – 180
0.3 – 2.8
2.5 – 6.5
0 – 2
0.3 – 0.6
2.0 – 8.0
1.8 – 4.0
3.3 – 6.2
65 – 75
70 – 95
10 – 13
10 – 24
5 – 12
45 – 75
10 – 11
0.2 – 0.4
36 – 46
14.0 – 15.0
36 – 44
0.2 – 0.8
4 - 8
*SAWTRI Compressibility Test
Style and character are judged subjectively, high quality style being described as solid (tightly) twisted ringlets (staples or locks), the curl or ringlet frequency being a measure of style, while character is described as the waviness or crimp frequency in the staple. Style without character, or vice versa, is undesirable, a good balance between these two characteristics being considered to be of paramount importance. Winter hair tends to exhibit a shorter and more variable wavelength of its curls than Summer hair, the pH of its aqueous extract also tends to be lower. Nevertheless, no effect of season per sé on processing performance has been observed, season only having an effect insofar that it affects the measureable mohair characteristics, such as diameter, length, style and character.
Burr and grass seed contaminants of mohair represent a particularly serious problem, and result in severe price penalties, and, where possible, burrs or excessive vegetable matter in the fleece have to be removed. Coloured (e.g. black or red) fibres, if present, could affect the finished cloth, particularly if light shades are dyed, and thereby the value of the mohair. Urine and certain types of soil and vegetable matter contain substances which stain mohair permanently, these affecting the dyeing and value of the mohair and the quality of the final product. Precautions must be taken to limit such stains, particularly urine stains.
Since the textile processing performance, applications and general quality, and therefore value and price, of mohair are largely determined by the measureable characteristics of the raw (greasy) mohair, it is hardly surprising that considerable effort has been directed over the years towards the objective (i.e. instrumental) measurement of these characteristics in greasy mohair to replace the subjective techniques traditionally used. As a result, it is possible today to measure the most important quality related characteristics, such as fibre diameter and yield, objectively with a high degree of accuracy.
Properties that need ultimately to be objectively measured, to characterise greasy mohair quality completely, include the following:
- Fibre diameter and its distribution (variability, e.g. CV)
- Yield (i.e. amount of clean fibre)
- Staple (or fibre) length and strength, and their variability
- Vegetable matter content and type
- Inorganic matter content (e.g. sand, dirt etc.)
- Medullation/kemp (objectionable medullated fibres)
- Mohair Fibre Physical and Related Properties
Fibre diameter (fineness)
Mohair fibres are generally fairly circular, almost round, the ratio of major to minor axes (i.e. ellipticity) generally being between 1 and 1.1, rarely exceeding 1.2, fibre cross-sectional size, or in practice diameter (fineness), being one of mohair’s most important quality and trading characteristics from the point of view of both price and textile quality, application and performance, with even a 1μm change in mean fibre diameter having a significant effect on price. Fibre fineness (diameter) largely determines processing behaviour and performance and product type (end use) and quality, having a major influence on the finest yarn and lightest fabric which can be produced, as well as on the handle and against body comfort of the fabric. As already mentioned, mohair from Kids varies from about 20 to 29µm, that from Young Goats from about 27 to 34µm and that from Adults generally from 30 to 40µm.
In addition to the mean fibre diameter, the variability (i.e. CV) of fibre diameter, particularly within the fleece, is also important, since it provides an indication of the uniformity (i.e. evenness) of the fibres and lot, and impacts somewhat on the processing performance and product quality. For individual goats, the CV of diameter for Summer Kids is about 28%, for Winter Kids about 26% for Summer Young Goats about 22%, for Winter Young Goats about 23%, for Summer and Winter Adults about 24%. In general, in a bale of mohair, the CV of diameter of the first shearing (Summer Kids) is higher (at around 30%) than that of subsequent shearing, as a result of the proportionally higher kemp and medullated fibre content of the fleeces. There is a tendency for CV of fibre diameter to decrease as mean fibre diameter (and goat age) increases, up to a mean fibre diameter of somewhere around 30 to 35μm, after which the reverse occurs. An overall ‘average’ CV of diameter is approximately 26%.
Because of the extreme importance of mohair fibre diameter (fineness), it is hardly surprising that mean fibre diameter, which can be measured by airflow, projection microscope, OFDA or Laserscan, is generally the main objectively measured and reported mohair characteristic, although the distribution of fibre diameter, in terms of CV, also has some textile significance. Although CV of diameter and degree of medullation can affect mean fibre diameter, as measured by airflow, the effect is small, and generally negligible within the normal ranges encountered for good quality mohair, except possibly in the case of Summer Kids.
A major step forward in improving and standardising the inter-laboratory measurement of mohair fibre fineness occurred upon the introduction of the Mohairlabs International Round Trials and associated issuing of Mohairlabs stamps in the early 1970s. Unfortunately, this was terminated in 2003, with the dissolution of the IMA. In 2009 a similar body to Mohairlabs, called International Mohair Laboratories (IMLA), was established in South Africa and became functional in 2011, being run by the Wool Testing Bureau (WTB) under the auspices of Mohair South Africa and a Steering Committee.
Although of secondary importance to fineness, fibre length has an important effect on processing route and performance and on yarn quality. The mohair staple has a very pronounced taper, indicating a fairly wide variation in single fibre length within the staple, the mean fibre length in the staple is close to that of the top, but only about 60% that of the staple itself (i.e. 0.6 x staple length), with a CV of single fibre length in the staple between about 40 and 70%. For worsted processing, the staple length should ideally fall between about 125 and 150mm, while for woollen processing it should be below 75mm.
Fibre tensile properties
Mohair has excellent tensile, resilience and elastic properties, it being possible to extend the fibre by up to 30% without damage. Fibre tensile properties are important from a textile point of view, fibre strength playing a role in fibre breakage during mechanical processing, including spinning, and in yarn strength, fabric manufacturing and in the ultimate strength of the fabric. Nevertheless, in the case of animal fibres, the absolute fibre strength (in gf or cN) increases almost linearly with the fibre cross-sectional area, more particularly the cross-sectional area of the thinnest (generally the weakest) place along the fibre. Therefore, fibre diameter, more specifically, that at the point of break, often the thinnest place along the fibre, has the main effect on the absolute strength of the fibre (i.e. the strength uncorrected for the fibre cross-sectional area). The fibre strength divided by the fibre cross-sectional area at the thinnest place or point of break (i.e. the intrinsic strength or intrinsic tenacity) is fairly constant for mohair. Variability of diameter (or cross-sectional area) along the fibre therefore has an important effect on fibre strength and breakage during processing, since the fibre will tend to break at its weakest place, which mostly corresponds to its thinnest place.
In practice, mohair fibre strength is generally expressed as tenacity, i.e. strength corrected for (divided by) the fibre cross-sectional area or linear density, usually expressed in gf/tex or cN/tex. Typically, mohair single fibre tensile tenacity, at an RH of 65%, temperature of 21°C and a gauge length of 20mm, is 17 cN/tex (14.5 cN/tex wet), with an initial modulus of about 400 cN/tex, and an extension at break of 45% (65% wet). Mohair bundle tenacity (Stelometer 3.2mm gauge length) is approximately 14cN/tex, at 65% RH and 20°C. Both single fibre and bundle tenacity are largely independent of the fibre diameter, although the initial modulus tends to increase slightly with an increase in fibre diameter.
Mohair generally has higher single fibre tenacity, initial modulus and extension at break than apparel wools, probably because of its lack of crimp and lower variation in along fibre diameter and crimp, and associated fibre characteristics. Nevertheless, lustre wools (e.g. Lincoln and Buenos Aires) have tenacities and initial moduli close to those of mohair.
Mohair fibre stiffness affects fabric handle, stiffness and drape, but is essentially a function of the fibre diameter, increasing with fibre diameter to the power of four (i.e. Fibre stiffness α Diameter4). Therefore, in practice, the fibre stiffness is almost solely determined by the fibre diameter, increasing sharply as the fibre diameter increases. It follows that if a fabric with a soft handle is required, the finest possible mohair needs to be used.
Fibre surface structure
Mohair, wool and hair are covered by a layer of sheet-like hardened cuticle cells (epidermal scales) which overlap each other, with their exposed edges towards the tip of the fibre (Fig. 4). The cuticle, or outer layer, plays an important role for the whole fibre because it is, on the one hand, exposed to environmental influences and, on the other hand, responsible for the surface properties of the fibre. The outer layer consists of a hydrophobic epicuticle, which provides the fibre with water repellency properties, i.e. repelling liquid water, while still allowing the fibre to absorb water vapour. Although, under a microscope, mohair is similar in appearance to wool, the epidermal scales (cuticle scales) of mohair are generally much less pronounced and only faintly visible (see also Section 10). They are anchored much more closely to the body of the fibre, i.e. they lie near to the stem or are piled more tightly upon one another, giving the fibre its well-known characteristics of low friction, low felting, lustre, gloss and smoothness. The cuticle scales are quite thin and flat, generally being less than about 0.6μm (typically 0.4μm) in thickness and hardly overlap.
Figure 4: Mohair Fibre Structure
(Adapted from drawings by; G.A. Smith, 1988, R.D.B. Fraser, 1972 and CSIRO)
In general, mohair has a relatively low scale frequency, with a relatively wide distance between the cuticle scale margins. The number of scales per 100μm is generally in the order of 5 compared with between 9 and 11 in fine wools, with the scale lengths correspondingly ranging from 18 to 22μm. The width to length ratio of mohair fibre scales is of the order 2, and independent of fibre diameter, the scale width generally being taken as equal to the fibre diameter.
As in the case of wool, mohair fibres have a lower friction when rubbed from the root to the tip (i.e. with the scales, termed with scale) than when rubbed in the opposite direction (i.e. from tip to root, termed against scale). The low against-scale friction of mohair, relative to wool, which is one of its distinguishing features, can be largely attributed to its relatively smooth (unpronounced) scale structure. Mohair has a very small directional friction effect (DFE), due to the extremely easy deformation of the thin distal edges in mohair and also to the absence of tilted outer surfaces and other high asperities. The against-scale (μ2) to with-scale (μ1) friction ratio of mohair is about 1.1 compared to about 1.8 for Merino wool. The ‘scaliness’ ((μ2-μ1) x 100%/μ1) of mohair, measured dry, is about 5 compared to about 60 for a fine Merino wool. When measured wet, the respective values are about 16 for mohair and 120 for Merino wool. It is these characteristics which give mohair its low felting propensity.
Fibre moisture related properties
The moisture and moisture management related properties of mohair play an important role in terms of its comfort and in its behaviour during wet treatment and drying. Although mohair is hygroscopic, and can absorb large quantities of moisture (over 30%) without feeling wet or damp, its surface is naturally water repellent (hydrophobic), largely due to the presence of a strongly bound thin surface layer of waxy or lipid material of the epicuticle, which requires strong chemical action to remove it. The hygroscopic nature of mohair allows moisture to diffuse through the fibre from the damp or moist microclimate near the skin, to the surrounding air, thereby keeping the air humidity near the skin relatively low and more comfortable. Temperature and moisture also play an important role in the visco-elastic properties of mohair, which in turn is related to wear properties, such as wrinkling. Table 3 illustrates the absorption and desorption of moisture by wool and mohair at different relative humidities.
Table 3: The Absorption and Desorption of Moisture by Wool and Mohair at Different Relative Humidities
(Source: J.B. Speakman, 1930, J. Soc. Chem. Ind., 49, T209)
Percentage Increase in Weight
Medullation and kemp
Good quality mohair, such as South African mohair, contain very little objectionable medullated (kemp type) fibres, although the presence of even a small amount of such fibres in a high quality mohair has a pronounced adverse effect on its value and price, since they can be a source of problems in many end-uses when they differ in appearance from the rest of the fibres which are not medullated.
Medullated fibres are characterised by having a central canal (medulla), containing cell residues and air pockets, running in either a continuous or fragmented form along their length (Fig. 5). Of all the types of medullated fibres that occur in wool and mohair, those collectively called kemp (i.e. more correctly referred to as objectionable medullated fibres), which generally have a relatively large medulla and are relatively coarse and oval in cross-section, are the most visible and unwanted in the final product. The term ‘kemp’ is probably a more familiar term, than objectionable medullated fibres, but it traditionally refers to the more problematic and extreme form of medullated fibre which is normally shed by the goat. Such fibres occur as short ‘kemp’, long ‘kemp’ and hetero-type fibres. The ‘short kemp’ is generally the most common, being short, chalky white, medullated, and pointed at each end, when it has fallen out and has not been shorn off. More recently, the term ‘objectionable medullated’ fibres, referring to those fibres which are clearly distinguishable by the naked eye due to their chalky white appearance, has replaced the term kemp, since in practice it is difficult, once the goat has been shorn, to identify a ‘true kemp’ fibre according to how it is traditionally defined.
Kemp or ‘objectionable medullated fibres’ are mostly much coarser than the parent population (on average about 1.8 times coarser than the mean fibre diameter of the parent population), with a medulla diameter to fibre diameter ratio mostly, but not always, greater than 0.6.
Figure 5: Cross- and longitudinal-sections of medullated fibres illustrating the cellular nature of the medullae
The main problems associated with the presence of objectionable medullated fibres are their chalky white appearance and their lighter appearance after dyeing, the difference in appearance being largely caused by the decreased length of the light path through the dyed fibre material and light refraction at the fibre/medulla interface and within the hollow network of cells (aerian vesicles). This, and not a difference in the dyeability of the solid fibre material (i.e. fibre wall) per sé, is considered to be the main cause of the different (paler) appearance of these fibres after dyeing (Fig. 6). Selective breeding is the best means to reduce medullated fibres, although mechanical processing (notably opening, carding and combing) also removes objectionable medullated (kemp) type fibres, particularly the shorter ones. Certain dye shades, e.g. yellow, are also better than others in camouflaging objectionable medullated (kemp) fibres..
Figure 6: Examples of dyed unmedullated mohair fibres and medullated fibres varying in their degree of medullation
- Mohair, Morphological, Chemical and Related Structures and Properties
Morphological structure and related properties
Mohair does not have a homogeneous structure, but has a highly complex, physical (morphological) and chemical structure (Fig. 4), ideally suited for protecting goats from extremes of heat and cold. The mohair fibre essentially consists of a cortex, comprising spindle shaped cortical cells or filaments, forming the solid and main part or bulk of the fibre, which is predominantly ortho-cortex, particularly in Kid Mohair, and epidermis (comprising cuticle cells) consisting of numerous overlapping epidermal or cuticle scales, which point towards the fibre tip and which enclose the cortex. Each cuticle scale is enveloped by a thin semi-permeable membrane, called the epicuticle, which comprises protein and ‘internal’ lipids. The cuticle scales, which are about 0.4μm thick, on average, form a protective covering for the cortex and consist of three layers, the hydrophobic epicuticle (≈ 5nm thick), exocuticle and endocuticle (Fig. 4). The cuticle cells are held (cemented) together, and also separated from the underlying cortical cells, by the Cell Membrane Complex (CMC), which consists of non-keratinous proteins and resistant membranes, and represents about 5% of the total mass of the fibre. The excellent resistance to wear of mohair is related to the regular structure of the macrofibrils (each up to 0.2μm wide), in its cortex. They, in turn, are made up of bundles of 10nm microfibrils in hexagonal packing, the microfibrils, or keratin intermediate filaments (KIF), which consist of eight keratins, and contain the organised alpha-helical structure, represent about 60 to 70% of the fibre mass, and provide the major extension stability to the mohair fibre. The absolute helix content of mohair is 35% (that of wool is about 30%), the highest of textile fibres and hair. The microfibrils are embedded in a matrix which is the main water absorbing component of the fibre, although both the microfibrils and matrix swell in water. The KIF (microfibrils) is only 50% crystalline, and contains 50% non-helical regions which form part of the matrix. Mohair is generally more amorphous (i.e. less crystalline) than wool, hence absorbing dyes more readily, and being more sensitive to chemicals.
Chemical composition and structure
Mohair fibres essentially consist of protein, water and internal and external lipids, and fall into the class of protein materials, known as keratins, characterised by long filament-like molecules and insolubility in dilute acids and alkalis. Keratin fibres, such as mohair, can be regarded as a long fibrous composite, comprising crystalline, relatively water impenetrable low sulphur helical micro-fibrils (keratin intermediate filaments), lying parallel to the fibre axis and embedded in a high-sulphur, non-helical, amorphous, water-penetrable matrix to form the macro-fibrils (Fig. 4). Keratin proteins are natural polymers, formed by the linking together of amino-acid units in long chains coiled in a helix (α-keratin) (Fig. 4). Mohair contains over 170 different proteins which consist of some 18 different amino acids joined together to form long polymer chains, each structural unit being joined by amide side groups, the different side groups imparting different chemical properties to the fibre. When the polymer chain is a protein, the amide group is called a peptide group, with, for example, a simple polypeptide produced from three amino acids. The individual polypeptide chains are joined together by a variety of covalent bonds, called cross-links, and non-covalent physical interactions, to form proteins. The proportions of certain amino acids are different for Kid and Adult hair.
Keratin fibres, such as mohair, are unique in that they have a high sulphur content relative to most other proteins. Their cortical cells consist of filaments of low cystine content (low sulphur proteins), surrounded by a non-filamentous matrix, containing two protein types, one cystine rich (high sulphur protein), the other rich in glycine and tyrosine (high tyrosine proteins) All mammalian keratin fibres, such as mohair, contain three main protein fractions, termed low-sulphur, high-sulphur and high-tyrosine proteins, with the low-sulphur proteins generally representing the largest proportion. All animal fibres, including mohair, contain approximately 3 to 4% sulphur, largely as cystine.
Mohair flame resistance
Mohair is difficult to ignite (its ignition temperature is around 600°C), and does not easily sustain a flame once ignited. If ignited, it tends to smoulder and char, rather than burst in flames, and it does not melt and drip, forming instead a good insulating foam-like ash. Its low heat of combustion (≈ 4900cal/g) and high moisture content add to its generally good flame retardancy properties. The Limiting Oxygen Index (LOI) of untreated mohair is about 24, with 27 generally being regarded as the minimum required to pass the vertical flame test. To meet certain severe flammability regulations and standards, such as for aircraft upholstery etc., mohair would require a flame retardant treatment, such as given to wool under similar circumstances.
- Mohair Processing
Figure 7: Typical sequence (flow diagram) for the worsted processing of mohair
Mohair is considered to be difficult to mechanically process, convert into tops, because of its smoothness (slipperiness) and lack of cohesion. The application of the correct types and levels of processing lubricants and additives (such as anti-statics), to increase friction and cohesion, and reduce static, and the selection of the most appropriate processing machinery and conditions (including regain and atmospheric) are crucial in the efficient processing of mohair into a quality product, including the spinning of very high quality mohair yarn at acceptable efficiencies. In converting mohair into yarn, similar machinery is used as in the case of wool. Considerable secrecy exists, even today, concerning the precise processing conditions used; firms which have built up this specialised knowledge and skills do not share it because it provides them with a competitive edge. Blending with wool is generally beneficial, improving inter-fibre friction, cohesion, bulk and processing performance.
Before scouring, individual mohair bales are often carefully sorted on screens, ususally according to style and quality, efficient sorting and blending playing an important role in processing behaviour and performance and in the eventual quality of the yarn, as well as in the predictability and consistency thereof. The fibre can then be willeyed (opening/cleaning/dedusting) before it is scoured, and this is advisable.
Scouring is a critical process in mohair production, and often it is at this stage that the ultimate state of the finished article is decided. As previously mentioned, mohair generally contains far less impurities than does wool (e.g. 4 to 6% of grease compared to about 15% for Merino wool), and scouring generally causes a loss in mass of between 15 and 20%. Mohair is generally regarded as chemically more reactive and more sensitive to chemicals (e.g. acids and alkalis), chemical conditions (e.g. pH) and heat, than wool. Because of this, and the need to preserve its lustre and colour, the scouring conditions for mohair are generally gentler than they are for wool, and scouring rates and temperature generally lower (e.g. 55ºC, or even 50ºC, in the first bowl, and decreasing in subsequent bowls). Excess alkali in the fibre can lead to discolouration in dyeing, and therefore less soda ash (e.g. only 2% in the first bowl), or preferably no soda-ash (alkali), should be used during scouring, with non-ionic detergents mostly being preferred today. The pH must be strictly controlled (below 9.5). A higher consumption of detergent is required to remove 1g of grease from mohair than from wool, the generally lower level of grease in mohair as well as its more oxidised nature, because of greater weathering, being the relevant factors. Relatively low drying temperatures (e.g. 80ºC) are advisable, drying the longer types to a regain of about 20%, and the shorter types to about 25%, the higher regain helping to control fly when carding the shorter types. Scouring yield varies typically between 86 and 90%.
For the Continental worsted system (French or rectilinear comb) of processing, which is very popular today, scouring to a residual grease content of 0.2 to 0.3% (DCM extractable) is advisable, and then spraying with a lubricant/antistatic to bring the total fatty matter level to between 0.7 and 0.9% (up to 1.2% for flexible card clothing) prior to carding.
Very little mohair (±2%) is normally classified as carbonising type, although in high rainfall areas and seasons it can rise to as high as 15%. Mohair with vegetable matter exceeding 3% is normally carbonised (e.g. 4 to 6% H2SO4, drying ≤ 100ºC and baking ≤ 130ºC). Nevertheless, the French (rectilinear) comb is very efficient in removing vegetable matter (seed), often making it unnecessary to carbonise seedy mohair, thereby better preserving the lustre, colour and tensile properties of the mohair. In such a case, it is preferable to willey (open) again prior to carding and to use a card with a more sophisticated forepart and one which is designed specifically for seed removal. Most carbonised mohair is sold for processing on the woollen system, although lightly carbonised mohair is sometimes also processed on the worsted system, resulting in a very good quality top.
Topmaking and spinning
It is generally easier to disentangle mohair than wool during carding (a regain of 12 to 14% for carding being recommended), with less fibre breakage in this process, although problems with static and fly generation often necessitate lower carding speeds, card losses generally ranging from about 3 to 7%. With frequent fettling, carding can reduce kemp by up to 20%. Mohair’s low cohesion (slippery nature) often necessitates that the fibres (slivers) be supported during processing, for example by springs in cans and by aprons, with delivery in the form of a bump top, rather than a ball.
Traditionally, mohair was processed on the Bradford worsted (oil-combed) system (drafting against twist), followed by flyer spinning. Today, the bulk of mohair is processed on the Continental or dry-combed (French/rectilinear combing), as opposed to the oil-combed, system, the rectilinear comb not being as effective as the Noble Comb, for example, in removing kemp. The removal of short kemps during processing, notably during carding and combing, normally does not represent a problem, whereas the removal of long kemp and heterotype fibres does.
The French (continental or dry-combed) system of drafting and spinning involves gilling, (usually two intersecting gillings, with a starting regain of 18 to 20%, and then ending with 17 to 19% prior to combing), French (rectilinear) combing, two finisher autolevelling intersecting gillings and double apron high draft drafting (drawing) and finally double apron worsted spinning (Fig. 7). It is possible to use either flyer (twisted) roving or rubbed (twistless) roving for subsequent yarn spinning. Staple lengths of 100 to 150 mm produce tops of around 80 to 120mm, respectively. Hauteur in practice generally ranges from about 70 to 115mm (typically 80/85mm), and top and noil yields typically from 75 to 85%, with noil ranging from 1.5 to 6%, being higher for finer hair. Resting (relaxing) mohair tops and rovings is considered to improve spinning performance and yarn properties.
Effect of fibre properties on topmaking performance
The processing behaviour and performance, as well as the spinning limits and yarn quality, of mohair are largely determined by the measurable fibre properties, notably the fibre diameter and length, and their variability. The staple profile and length distribution, together with the fibre diameter, can, to a large extent, be used to predict the fibre length distribution of the staple and the top, with finer and longer fibres generally performing better in this respect, even though they tend to break more during carding, and produce more noil during combing. The fibre length in the top is close to that in the grease, being about 60% that of staple length.
The CV of fibre length in the top can vary from about 35 to 60%, depending on the greasy fibre length and diameter and their variability, as well as on the mohair type and style.
The fibre diameter in the top is typically about 0.5μm coarser than that in the greasy mohair at the fine end of the scale (e.g. 25μm Kids) and about 1.0μm at the coarser end of the scale (e.g. 35μm Adults), due to the preferential breakage and removal of the finer and shorter fibres.
The goat age and season only affect textile processing performance and product quality insofar as they affect the measurable fibre properties, such as fibre diameter, length and waviness, and their variability. Mohair of better style and character generally produces less card waste and noil and longer tops, with fewer short fibres and less variation in fibre length, and better spinnability, as well as more even and stronger yarns, largely due to associated differences in wave frequency, staple length, and its CV, and CV of fibre diameter.
Worsted spinning performance
Spinning performance generally improves with a decrease in mean fibre diameter (even at a constant number of fibres in the yarn cross-section) and an increase in mean fibre length. The finest yarn which can be spun largely depends upon the mohair fibre diameter or fineness, traditionally expressed in terms of ‘quality or quality counts’, and these are related to the minimum number of fibres in the yarn cross-section (usually around 40 or 50), coarser and/or shorter fibres generally also being more likely to cause problems in terms of yarn hairiness. A spinning draft of between 15 and 25, with larger ring diameters and heavier travellers, than for wool, are generally recommended. Yarn hairiness and irregularity increase, and yarn strength decreases with an increase in fibre diameter, and with a decrease in fibre length.
Woollen processing system
Most of the shorter and carbonised mohair, and also a certain amount of longer hair, as well as mohair waste, such as carbonised noils, are processed on the woollen system, very little, if any, vegetable matter being essential. In woollen spinning, mohair shorter than about 75mm staple length is generally used, which contrasts with the worsted system, where the staple length is generally 90mm and longer, with a staple length of some 120mm and longer, mostly required.
Fancy (novelty) yarns
Mohair is used to particular advantage in fancy or novelty yarns, such as loop, knop, brushed, bouclé, flame, snarl, slub and gimp, possibly involving yarn brushing, where its properties provide outstanding aesthetic appeal and comfort. Such yarns are used in blankets, stoles, shawls, scarves, knitwear (sweaters, cardigans, jerseys etc.), travel rugs, curtaining, table coverings, upholstery, furnishings, pram covers, women’s dress-wear, suitings and coatings, the yarns and /or fabrics often being brushed. Adult hair is often used to form the loops of bouclé yarn properly, two or three yarns (wool and/or nylon) being used to securely anchor and bind the mohair yarn loops.
- Knitting and Weaving Mohair
Excessive handing (e.g. rewinding) of yarns and packages, prior to knitting or weaving, must be avoided as far as possible, as also excessive and rough yarn guides, sharp angles etc. Generally, mohair yarn is converted into knitted and woven fabrics using similar equipment as for wool, though sometimes in a modified or adapted form and under special conditions, which allow for the more hairy, and often weaker, nature of the yarns.
Mohair, mostly the medium and coarser grades, is very popular in knitting, both hand and machine, it being important to reduce the yarn friction by lubrication or waxing, and to take special precautions on the knitting machine to handle the generally hairy and fancy nature of the mohair yarns. It is preferable to use balanced two-ply yarns to reduce pilling, fibre shedding, spirality and stitch distortion. Commonly 5 to 10 gauge V-bed knitting machines are used. Longer and finer mohair generally produce better quality fabrics.
Woven mohair apparel fabrics generally comprise a combination of mohair (generally the finer grades ≤ 28μm) and wool (sometimes also silk), with, for example, singles mohair yarn as weft, and two-ply wool yarn (sometimes sized singles yarn) as warp. For lightweight ‘mohair’ suitings (≈ 170g/m2, men’s and ladies’ outerwear), a singles mohair weft yarn (e.g. 40tex, 26µm/70mm mohair, possibly with 10% wool), together with a two-ply wool warp (e.g. R40tex/2, 20µm/70mm wool), to give a 50/50 mohair/wool blend, in a 1/1 plain weave, is fairly popular. For lightweight woven outerwear (e.g. suitings), the mohair used is typically about 25/26μm, and the wool typically about 20/22μm, with Hauteur generally around 70mm.
- Dyeing and Finishing Mohair
Dyeing and finishing represent crucial stages in the manufacture of mohair products of the outstanding quality and appearance associated with items bearing the label ‘mohair’, with reactive, acid and metal complex dyes being popular. It is generally the case that firms which dye and finish mohair also dye and finish wool, and hence similar machinery are used for the two fibres. Furthermore, it is rare to find pure (i.e. 100%) mohair fabrics, particularly woven fabrics, it being mostly present in blends with wool, often yarn blends, which means that the dyeing and finishing machinery and conditions used must be suited to both fibres. Mohair generally has a higher rate of dye uptake than wool of similar diameter, and, for the same dye uptake, has a deeper shade than wool, possibly due to its smoothness and lustre. It is best to dye it at a pH within the isoionic region, around pH 4 to 5.
There is a vast literature on the dyeing and finishing of wool, much of which is to a large extent also applicable to mohair. There is far less literature and public knowledge available on the specialised conditions and procedures required for the dyeing and finishing of mohair products, most such knowledge being a well-kept secret. In general, milder conditions (particularly temperature and time) are used for the dyeing and finishing of products containing mohair than for pure wool products, partly because of the need to conserve the lustre of mohair and partly because mohair is generally more sensitive to wet treatments than wool. It is common practice to dye at temperatures below the boil, preferably below 90ºC, and to limit the time of dyeing at high temperatures, so as to curtail any adverse effects on lustre and other desirable properties. It is also possible to limit damage to the fibre by using fibre protective agents. A typical dyeing and finishing route, for a mohair/wool lightweight (men’s and ladies’ outerwear) suitings fabric would be; piece dyeing, cropping and singeing. For a yarn dyed mohair/wool men’s suiting fabric (e.g. 210g/m2), finishing could typically involve; singeing (both sides), crabbing (e.g. water at 75ºC), rope scouring, heat setting (e.g. 185ºC for 30 to 40 sec.), humidifying, cropping (shearing), pressing (continuous) and pressure decatising. Pressure decatising is used to stabilise lustre, set the fabric, improve dimensional stability and fabric flexibility, and involves, for example, a 0.8 to 1 bar pressure, at 120 - 125ºC for two minutes at a pH of 6, and a regain of 12 to 15%.
- Mohair Fabric Properties
Comfort related properties
Mohair fibres are hygroscopic, which means they absorb moisture (water vapour), and they can, in fact, absorb more than 30% of their weight in moisture, without feeling wet or damp, this being important in terms of comfort. Mohair also gets warmer (generates heat) when it absorbs moisture at a higher humidity of the air, the heat so produced is by a phenomenon known as ‘heat of sorption’. Conversely, when mohair loses moisture, by desorption in a low humidity atmosphere, it becomes cooler, thereby cooling the wearer. This can reduce the effect of sudden changes in temperature and greatly enhances insulation and comfort. When, for example, 1 kilogram of an animal fibre, such as mohair or wool, takes up 35% of water vapour, in a saturated atmosphere, it very quickly produces 960 kilojoules of heat, equivalent to about eight hours of the heat output by an electric blanket. When the reverse occurs, i.e. when mohair loses the moisture in a dry atmosphere (by desorption), it will cause an equivalent cooling effect.
Although, as already stated, mohair fibres are hygroscopic, the epicuticle of the mohair fibre is in fact hydrophobic, imparting water ‘repellency’ properties to the fibre, allowing liquid perspiration (sweat) to be ‘repelled’ and to evaporate, rather than be absorbed by the fibre, resulting in a highly desirable and comfortable cooling effect, due to the cooling effect produced when a liquid (e.g. water or perspiration) evaporates, this being particularly important in socks and other ‘high activity’ applications..
Mohair is widely recognised as having very good wrinkle resistance and recovery, which, together with its stiffness, make it an ideal fibre for use in comfortable light-weight tropical suiting type fabrics. Lightweight mohair suiting type fabrics typically have a clear smooth surface and are relatively stiff, minimising fabric contact with the skin and also the amount of air trapped between skin and fabric, making them cool to the touch, with the desorption effect enhancing cooling, thus adding to the coolness and comfort of the garment in hot and humid environments. Hence the popularity of lightweight mohair suitings in hot and humid countries, like Japan.
To achieve the opposite effect to the above, and produce warm, soft and comfortable garments, such as sweaters, stoles, scarves and blankets, fabrics with a long loose pile , hairy or loop surface are used, so that a great deal of air, which is a very good heat insulator, is trapped between the wearer and the environment. The long surface fibres also bend and buckle easily, thereby mitigating against the stiffer nature of the relatively coarse mohair fibres, popularly used in such applications.
Woven mohair fabrics, when properly designed, engineered (e.g. not too tightly woven) and finished (e.g. relaxed and aged), generally have good wrinkle resistance and recovery properties, except under very high humidity and damp conditions.
Drape and stiffness
Fabric drape and stiffness are directly related to the fibre diameter and also to the fabric structural parameters (e.g. weave structure and tightness or compactness) and finishing (e.g. state of relaxation), fabric stiffness and drape coefficient increasing with an increase in fabric tightness (cover factor) and fibre diameter, the stiffness of a mohair fibre increasing with fibre diameter to the power of four (i.e. stiffness α diameter4).
Wear performance and durability
Mohair is renowned for its hard wearing and durability properties, not only in apparel but also in carpets, curtaining and upholstery etc., much of which is due to its excellent elasticity and flexibility. Because of its general smoothness and low static propensity (except under dry conditions), mohair does not allow dirt to collect readily, and stains are generally fairly easily removed. Generally, longer fibres produce less hairy and stronger fabrics and yarns which are much more abrasion resistant and less prone to pill, while coarser fibres reduce pilling as well as yarn and fabric strength, but tend to improve abrasion resistance.
Due to its excellent moisture absorption, water (perspiration) repellency, wicking and other moisture management related properties, mohair is comfortable when present in socks, particularly when combined with certain other fibres, resulting in much less sweat being produced, and in a less slippery, and drier, more comfortable micro-climate around the foot, also providing a micro-climate less conducive to the growth of micro-organisms, such as fungi, resulting in less odour build up during wear. For example, mohair, in blends with wool, bamboo and other fibres, has found significant application in comfort socks containing cushion soles, particularly for active sportswear (e.g. cricket, mountaineering etc.) and medical applications, e.g. for diabetics, where its good moisture management and overall comfort properties are much sought after and highly beneficial.
Because of its good moisture absorption and management properties, mohair bedding products can produce a deep and comfortable sleep, provided, however, they are correctly designed and ‘engineered’.
- Mohair Fibre Identification
Because of mohair’s excellent quality image and reputation, particularly that of South African or Cape Mohair, and its premium price differential, unscrupulous dealers are sometimes tempted to substitute relatively less expensive lustre wools for mohair. To ensure and protect the integrity and quality image of mohair, it is therefore important to be able to have a reliable method of distinguishing between wool and mohair, and also of accurately quantifying and verifying the blend composition of products containing mohair. Although a great deal of research has gone, and is still going, into finding and developing methods of distinguishing between wool and mohair, the only one which is internationally accepted at present, is the one developed by DWI, which is based upon the cuticle scale height measured by Scanning Electron Microscope (SEM), as illustrated in Fig. 8.
Figure 8: Distinguishing between mohair and wool on the basis of cuticle scale height, measured by SEM (Source: DWI, 1992)
- Mohair Applications
The textile application of mohair goes back many thousands of years, the fibre finding application in almost every conceivable textile end-use, a detailed list of mohair applications having been given by Hunter [1,2]. Mohair, is, however, fairly sensitive to global economic conditions and fashion trends. In lean worsted-type light-weight tropical suitings, mohair is regarded as a cool fibre, whereas in brushed articles, such as shawls, stoles, rugs, sweaters and blankets, mohair provides warmth without weight. Mohair’s characteristics of hard-wearing durability, resilience or springiness, crease resistance, moisture absorption, comfort, lustre and smoothness make it ideally suited to many applications in apparel and interior textiles, such as upholstery and any pile fabric (e.g. plush, velours, velvet and moquettes etc.), furnishings, rugs and curtains, and it is virtually unsurpassed for general durability, recovering very quickly after being crushed.
Mohair, often in blends with other natural fibres, notably wool, with which it blends well, is used to great advantage in knitwear (ladies sweaters) and hand knitting, mostly in brushed, loop or some other fancy form, brushing imparting softness and warmth without weight. Knitwear (all forms of machine and hand knitting) represents some 70% of mohair’s end uses. Mohair also finds significant application in woven suiting and coating type fabrics (≈ 20%), particularly in men’s light–weight summer (tropical) suitings, where it provides the wearer with considerable comfort and good wrinkle resistance. Other significant end-uses of mohair include velours and upholstery (≈ 5%) and household textiles (≈5%), including blankets, carpets, curtaining etc.
- Further Reading
More detailed information, as well as references can be found in the following sources:
- L. Hunter: ‘Mohair: A review of its properties, processing and applications’. CSIR Division of Textile Technology, Port Elizabeth, International Mohair Association (Ilkley) and The Textile Institute (Manchester, UK), 1993
- L. Hunter: ‘Mohair’, Chapter 2 in ‘Silk, Mohair, Cashmere and Other Luxury Fibres’, (Ed. R.R. Franck), Woodhead Publishing, (Cambridge UK), 2001
- L. Hunter: ‘Mohair, cashmere and other animal hair fibres: Chapter 9 in ‘Handbook of natural fibres Volume 1. Types, properties and factors affecting breeding and cultivation’ (Ed. R.M. Kozlowski), Woodhead Publishing Ltd (Cambridge, UK), and The Textile Institute (Manchester UK), 2012