LPT 312: Abattoir Practices and Animal Products Technology (1+1)

QUALITY CHARACTERISTICS OF WOOL

• The important quality characteristics of wool are colour, fibre length, fibre diameter and clean dry yield.
• These characteristics account for nearly 80% value.
• The colour of wool is important because presence of any pigment markedly decreases the possibilities of dyeing.
• The ideal colour is white or creamy white with conspicuous lusture.
• Canary staining or yellowing of wool is a general problem in Indian wool.
• It is caused by bacterial action at high pH and low grease content.
• Fine wool has a fibre diameter of 17-18mµ (micron) whereas in coarse wool it may be nearly twice (35 – 38mµ)/ Wools less than 30mµ fibre diameter (non-medullated) are only suitable for clothing textiles.
• The coarse wools are generally used for carpet manufacture.
• To determine the proportion of fibres of each type, a representative sample containing atleast 200 fibres of a fleece are taken and sorting is done against a black background such as black velvet.
• All fibres showing chalkiness to the naked eyes are counted as hairs, unless those are kemps.
• Within the laboratory, medullation can be assessed by immersion of wool sample in xylol and examination under high magnification.
• Fibre length is an important parameter from spinning point of view.
• In temperature climate, it is the growth of staple during 12 months of age.
• Fine wool is generally less than 6cm comes in coarse grades.
• Clean dry yield refers to the yield of pure wool removing natural grease, vegetable material (grass seeds, burr etc) and soil.
• These impurities can range even upto 20 per cent.
• Further, strength of the fibre is also an important property.
• It is affected by low plane of nutrition and chronic infection especially helminthiasis.
• In field conditions, holding the ends of the staple between the fingers and giving a sharp tug measure it.
• In fine wool crimp, which refers to the waviness of wool fibre, is also considered as an important characteristic.
• It is measured in number of crimps per unit length.
• As far as elasticity is concerned, a fine wool fibre can stretch as much as 70% beyond its original length before breaking.
• Some defects generally encountered in wool are hairiness, impurities, skirting, lack of uniformity and cotts (pressing together of coarse fibres).