WOOL QUALITY ASSESSMENT
Purpose : The potential range of end products that wool may be used for is dictated by many qualities, including fineness, clean wool yield, length, color, and uniformity. Fineness, or grade, is of primary importance in determining market value of raw wool. Finer (smaller diameter) wools usually are associated with more expensive, lighter weight fabrics, while coarser-fibered wools (larger diameter) usually are used in bulkier sweaters, blankets, and carpets.
Skirting : Skirting is done after shearing and prior to judging of the quality of the wool. It involves removal of the objectionable parts such as tags, leg pieces, face, neck pieces, bellies, locks and stained portions from the body of the fleece. In addition, any applied colour or pigmented wool should be taken out and kept separately. Similarly, heavy burry wool found below the jaw should be picked. This will help the farmer in realizing a better price for his wool.
Parameters of judging wool quality :-
1. Fineness/Grade : In general, grade refers to the average diameter or thickness of the fibers. Three systems of wool grading are commonly used : the American or Blood system; the English or Spinning Count system; and the Micron system. The American Blood Grade System was developed in the early 1800s and originally represented the amount of fine-wool Merino genetics (Spanish origin) present in the native coarse-wool sheep. The English system of grading wool uses a measurement called the “spinning count” and is based on the number of “hanks” of yarn which could be spun from one pound of clean wool on the equipment available at the time the system was developed. Increased emphasis on an exact and highly descriptive method of describing wool grade has produced a measuring system in which individual fibers are accurately measured. The unit of measure is the micron.
Traditionally, the standard method of measuring these fibers is by a microprojection technique in which short longitudinal sections of the fibers are projected onto a screen at 500-fold magnification. Technological advancements like electro-optical and image analysis machines have greatly improved the efficiency and accuracy of fiber diameter measurement.
All three systems are measures of average fiber diameter and can be used interchangeably as shown in the table below, but the micron system is the system used internationally and preferred by wool buyers and manufacturers.
The classification of Indian wool as per diameter is as below:-
2. Staple length : It is the total length of a fibre in its natural condition. It is obtained by measuring the natural staple without stretching the crimps out of the fibre.
3. Fibre length : It is the total length of a wool fibre after removing the crimps or waviness by straightening it.
4. Crimpiness : It refers to the waviness of the wool fibre. Its number varies from 2 to 12 per cm depending upon the quality. It is a valuable property in spinning and increases the elasticity of the yarn and fabric. Crimps are more pronounced in fine wool.
5. Elasticity : The property of wool fibres to return to their original or natural form after being stretched or compressed. Wool is quite elastic, and therefore, resists wrinkling, bagging and tearing.
6. Kemp : It is a chalky, white, lusterless and dead fibre growing with wool which resists dyeing. It should be rejected.
7. Heterotype : Fibres which occur in the fleeces of indiscriminately bred sheep. They show, at different parts of their length, the physical structure and characteristics of both wool and hair.
8. Lustre : It is the ability of wool to reflect light. Wool with lustre, when dyed, has a brighter appearance than wool without lustre. Coarse wool with fewer scales has more lustre than fine wool because of smoothness of fibre.
9. Strength : It is the property of wool fibre to undergo processing without breaking. Wool fibre and fabrics are usually strong and durable.
10. Conductivity : Wool is one of the best fibres for retaining body heat and also for keeping external heat out. This is because of its insulating nature i.e. it is a poor conductor of heat.
11. Dyeing properties : Wool is one of the easiest fibres to dye because dyes penetrate the fibre easily and remain permanently.
12. Softness : Softer fibres consist of numerous, small scales which fit over one another loosely and produce fabrics which are softer to touch.
13. Inflammability : Wool is slower to burn, and on burning, it gives off a pungent odour and forms a bead when burning ceases.
14. Action of chemicals : Alkalis weaken the wool and may even dissolve it completely. Dilute acids do not act upon wool, and wool is generally dyed with acid colours.
15. Moisture : Wool readily absorbs and gives off moisture. Under normal conditions, the moisture content varies from 12-17 %.
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Disclaimer : The information on this site is meant as an aid to students and fellow veterinarians and should be used for educational purposes only. The views expressed are solely that of the author and should not be construed to be that of his employer or any other organization.