Wool Processing

Current Version

WOOL-482-582 was originally issued in 2008. It was created with funding provided by the Sheep CRC supported by AWET. UNE, charged with creating the unit, initially presented the material with lecture notes in DOC and PDF format, and included copies of of many of the references appended to the lectures. Presentations in Powerpoint format were also provided for each topic. There are 29 topics in the original module

Funded by AWET the original version of this module has been substantially edited and reduced to 16 topics. This has removed a considerable amount of detail in order to provide a broader overview of this important topic.

This module includes 16 topics.


Topic 01: Overview of Early Stage Processing

This topic provides an overview of the steps involved in the early stage processing of wool (ESP), ie, the conversion of greasy wool into yarn. Subsequent topics in this unit provide more details on each processing step in early stage processing, as well as the steps involved in late stage processing.

On completion of this topic you should be able to:

  • Outline the main wool processing systems, from greasy wool through to finished yarn;
  • Describe the essential features of the worsted, woollen and semiworsted processing routes, using an appropriate flow diagram;
  • Explain the similarities and differences between these routes with respect to (a) the raw material requirements, (b) complexity of each route, and (c) the properties and uses of the yarn produced by each; and
  • Describe the essential differences between a woollen and worsted card.

Topic 02: Wool Scouring Principles and Methods

This topic covers the wool scouring process, presenting the principal objectives and functions of the modern industry. Wool scouring is the only operation, other than carbonising, which is unique to the early stage processing of wool fibre. Synthetic fibres are not contaminated to any significant extent, and therefore are not scoured.

On completion of this topic you should be able to:

  • Describe the nature of the main contaminants of raw wool;
  • List the objectives of wool scouring;
  • Describe sequence of operations in a scouring plant;
  • Explain how a detergent removes grease from wool fibres;
  • List the factors that affect the quality of scouring;
  • Explain the following:
    • Preparations of wool for scouring (ie, opening, blending, and cleaning operations);
    • The parts of a minibowl and their role – How the various contaminants are removed in aqueous scouring
    • Post-scouring operations (drying, cleaning, packaging);
    • How scouring effluent is treated to minimise waste and extract wool grease; and
  • Explain the different requirements in the scouring of fine and coarse wools, and the scouring lines used for each type.

Topic 03: Scoured Wool Quality and Testing

This topic looks at the full range of certificated tests that are routinely carried out on scoured wool consignments in Australia and New Zealand. These are: yield, vegetable matter content and solvent extractables, fibre diameter, colour, regain and length after carding. In addition, the in-scour tests for quality are included; the rapid tests for grease (solvent extractables) and regain, and the use of NIRA technology.

On completion of this topic you should be able to:

  • Explain why testing is important to the wool industry;
  • Describe the sampling techniques appropriate to scoured wool testing;
  • Outline the yield test procedures, in particular the determination of wool base, ash content, vegetable matter content and solvent (i.e. ethanol and DCM) extractables;
  • Explain why and how various yield calculations are carried out, for presentation on a test certificate • Describe briefly the modern instruments used for fibre diameter measurement, their operating principles and the results they produce;
  • Outline the colour measurement techniques applicable to wool, including preparation, instrument requirements and the form in which results are reported;
  • Explain the sampling, preparation and testing steps for the Length After Carding test;
  • Calculate the regain of a wool sample, given the original mass and the dry mass;
  • Outline the rapid tests used in the scour for moisture and residual grease measurement; and
  • Describe how NIRA techniques have revolutionised in-scour quality management.

Topic 04: Wool Carbonising

This topic looks at Carbonising, the chemical process used to remove vegetable matter (VM) from wool. The VM, which may be seeds, twigs, burrs, grass etc., is predominantly made up of cellulose, hemicellulose and lignin whereas wool is principally protein. The carbonising process exploits the difference in the stability of proteins and cellulose to the effects of mineral acids.

On completion of this topic you should be able to:

  • Explain why certain wools need to be carbonised
  • Outline the basic principles involved in the carbonising process
  • Describe the parameters to be controlled during the process
  • Discuss the problems which can be encountered in carbonising and the adverse effects they can have on the final product.

Topic 05: Principles of Wool Carding

Irrespective of which of the three routes (woollen, worsted or semiworsted) is used to process wool into yarn, the card (or carding machine) plays an essential part. It separates the entangled clumps of fibres into a web of individual fibres by working them between a series of closely spaced, moving roller surfaces which are covered with pointed wire, pins or teeth (the card clothing). Important considerations in carding are the processes of fibre individualisation, formation of the web, the extent and configuration of the fibres in the web, and the degree of fibre damage occurring during carding. These are important because, in processing stages after to carding, excessive fibre breakage and poor fibre configuration (i.e. straightness) may lead to unacceptable yarn irregularity and imperfections.

On completion of this topic you should be able to: • Identify the key rollers in a card, explain their functions and compare their speeds • Describe the various card roller interactions and their purposes • Explain how fibres gain a hooked configuration in card sliver, and how these hooks are subsequently removed • Describe the process of fibre breakage on a card and the factors that influence the level of breakage • Explain the terms collecting fraction and delay factor, and their relevance to the mixing ability of a card • Describe, with the use of a suitable diagram, the effect on carding production of a rapid change in feed rate. • Describe a nep, and outline the factors that contribute to nep formation in carding.

Topic 06: Drafting and Gilling of Fibrous Assemblies

In wool yarn manufacture, an integrated series of operations is required to convert disorganised tufts of staple fibres into an organized twisted strand. Carding commences the process, but further steps are required before the yarn can be spun. The fibres are delivered to the next processing stage by a worsted and semiworsted card in the form of a sliver. Gilling improves the straightness and alignment of the fibres in a sliver, while drafting reduces its linear density (or count) by the desired amount.

On completion of this topic you should be able to:

  • Explain the principles of roller drafting and the devices used to achieve this;
  • Define the terms associated with the drafting process and distinguish between calculated and actual drafts;
  • Describe the purposes and method of doubling;
  • Explain how periodic irregularities are introduced into slivers during roller drafting and pin drafting, and the factors that may influence thi;
  • Describe the various methods of controlling fibre in drafting;
  • Explain the purpose of autolevelling of slivers and the devices used for this process • Describe the essential features of a gillbox, comparing the screw drive, chain gill and pinned roller mechanisms;
  • Explain the interaction of the faller pins with the front and back rollers to improve the fibre alignment and straightness in gilled slivers; and
  • Outline how faller bar marks occur in gilled slivers.

Topic 07: Wool Combing

Wool combing is a comprehensive term when used in its widest sense, and it embraces all the operations carried out in a topmaking plant. It includes the processes of raw wool scouring, drying, carding, backwashing and preparer gilling. Then follows the actual combing operation and the sequence of topmaking processes concludes with two gilling steps called top finishing (or finisher gilling). Combing is not included in the semiworsted or woollen processing routes.

Wool combing, the single process, is indispensable in the manufacture of a worsted yarn. The card has disentangled the fibres in the mass of scoured wool and has mixed them in a roughly parallel formation. However, during the carding process many fibres will have been broken, and the card sliver will consist of a variety of fibre lengths. Some vegetable matter will have been removed but fragments remain.

Gilling is able to mix, align and straighten fibres but a gillbox has no capability to remove short fibres or vegetable matter from sliver. Combing enables finer, stronger, more uniform and less hairy yarns to be spun at higher efficiency.

On completion of this topic you should be able to:

  • Outline the objectives of wool combing;
  • Describe the design of a typical rectilinear comb;
  • Explain the steps in rectilinear combing – feeding, initial combing, final combing and drawing off, and sliver formation;
  • Discuss the means by which noils are removed, and the balance required in setting the amount to be removed;
  • Explain the purpose of re-combing;
  • Calculate: tear ratio, noil(%), romaine, regain and combing production; and
  • Discuss the factors that affect the combing quality of fine wools.

Topic 08: Fundamentals of Yarn Technology

Carbonising is the chemical process which is used to remove vegetable matter (VM) from wool. The VM, which may be seeds, burrs, grass etc., is predominantly made up of cellulose, hemicellulose and lignin whereas the wool is principally protein. The carbonising process makes use of the difference in the stability of proteins and cellulose to the effects of A yarn is a relatively strong and flexible assembly of fibres or filaments, with or without twist. It is an important intermediate product between fibres and fabrics. Yarn technology deals with the manufacture of various types of yarns consisting of different fibres and fibre arrangements, and the properties of these yarns. The fundamentals of yarn technology cover basic topics on yarn count, twist, yarn structures, and yarn types.

On completion of this topic you should be able to:

  • understand and apply the definitions for different yarn count systems;
  • convert between yarn count systems;
  • explain the effect of moisture on yarn count results;
  • describe the effect of twist on certain yarn and fabric properties;
  • explain the importance of surface twist angle and of selecting the right twist factor for different yarns;
  • calculate the twist contraction;and
  • apply the basic rules that apply to twist measurements.

Topic 09: Spinning

While the term ‘spinning’ is commonly used to describe the entire yarn-making process, in this topic the more specific meaning applies, i.e. the formation of yarn by drafting a strand of fibres, inserting twist and winding the yarn onto a package. The ultimate aim of spinning is to produce a continuous, cohesive strand of fibres (i.e. a yarn) of the required linear density (count) and which has good evenness, tensile properties and a minimum number of faults.

On completion of this topic you should be able to:

  • Describe the preparation of the materials required for the three main spinning systems;
  • Explain the purpose and device used for drawing to form a roving;
  • Outline the principles of ring spinning, in particular the functions of the key parts of a spinning frame;
  • Explain the role of the traveller and the parameters that control its performance;
  • Describe what an end-break is, and why it occurs • Outline the process of package formation;
  • Compare the essential features of worsted, semiworsted and woollen ring spinning frames;
  • Explain the purpose of the false twist device in woollen spinning;
  • Explain the purpose and means of drafting in worsted and semiworsted spinning;
  • Describe the methods used to dye wool yarns; and
  • Outline the steps required after spinning to ready a wool yarn for weaving or knitting, in particular winding, clearing and twisting.

Topic 10: Recent Developments in Spinning and Non-wovens

Ring spinning (which is discussed in Topics 1 and 9) remains the dominant form of spinning wool into yarn, primarily because it is regarded as producing a superior yarn to alternative spinning systems. However, a number of modifications to long staple ring spinning have been developed in recent years to provide more versatility and to reduce costs. These include methods of eliminating two-folding (or plying) in the production of weaving yarns, with the ultimate aim of producing as a yarn as possible on a spinning frame without resorting to two-plying or sizing.

The manufacture of nonwoven fabrics involves converting fibres into fabric, eliminating the need for yarn to be spun as an intermediate step. The ability of wool to felt has enabled nonwoven (ie, felted) products to be made for centuries. However, more modern processes involving needle punching and stitch bonding enable a range of nonwoven products by mechanical means.

On completion of this topic you should be able to:

  • Describe the latest developments in worsted spinning including ring, collapsed balloon, and compact spinning;
  • Outline bicomponent yarns, two-folding, winding and clearing;
  • Outline developments in non-woven processing; and
  • Describe cross-lapping, and compare bonding systems such as needlepunching, stitch and hydroentanglement.

Topic 11: Weaving technologies and structures

While the term ‘weaving’ is mostly used for the process of interlacing two sets of yarns (warp and weft) on a loom to form a woven fabric, it is actually a series of processes which converts yarn into a fabric that is suitable for tailoring.

Shuttle looms have been the traditional machines for weaving over many centuries, and are still widely used around the world today, especially in developing countries. However, over the past three decades, shuttle-less looms have taken the lead position in weaving machinery. Speed and versatility have been the main thrust of the developments.

By the end of this lecture, you should be able to:

  • Briefly explain the basic stages in the weaving of fabric;
  • Draw a diagram of a basic loom, showing the key parts • Outline the warping and drawing-in steps;
  • Explain why yarn sizing is required and how this is carried out;
  • Outline the sequence of steps in the weaving cycle and the purpose of each step;
  • Describe the different shedding mechanisms and the advantages and disadvantages of each;
  • Describe and compare the various mechanisms used for weft insertion, both shuttle and shuttleless weaving; and
  • Discuss the main yarn interlacing structures in woven fabrics, their characteristics and uses.

Topic 12: Machine Knitting

Knitting as a method of converting yarn into fabric begins with the bending of the yarn into loops. These loops are then intermeshed with other loops of the same open or closed configuration in either a horizontal or vertical direction. These directions correspond respectively to the two basic forms of knitting technology – weft and warp knitting.

On completion of this lecture you should be able to:

  • Outline the fibre and yarn requirements for machine knitting, with an emphasis on the suitability of wool yarns;
  • Describe and explain the function of key parts of a knitting machine;
  • Explain the features, operation and products of the main types of knitting machine and compare their advantages;
  • Compare knitted and woven fabrics, in particular their respective advantages and disadvantages;
  • Briefly describe the purposes and methods of finishing treatments commonly used with knitwear; and
  • Describe, using simple diagrams, the most common knitted loop structures and their specific contributions to fabric appearance and performance.

Topic 13: Wool Carpet Manufacture

A carpet is a textile floor covering that combines an attractive appearance with warmth, and comfort for standing, walking or reclining on. Carpets bring many diverse benefits to homes and public spaces. The top layer of the carpet, which is subjected to foot traffic, is called the pile. It composed of millions of yarn segments, arranged in a compact formation as short loops or upright tufts. Today there are three main methods of making wool (and wool rich) carpets and rugs: hand-knotting, weaving and tufting.

On completion of this topic you should be able to:

  • List the key attributes of an ideal carpet fibre;
  • Briefly outline the properties of wool that make it a good fibre for carpets;
  • Compare the advantages and disadvantages of wool with the other major carpet fibres • Describe the wool components of a typical carpet yarn blend;
  • Outline the raw material requirements for the various types of tufted and woven carpets;
  • Describe the main route by which wool carpet yarn is produced;
  • Briefly discuss the colouration options for carpets • Explain the purpose of yarn setting and how it is carried out;
  • Define the terms used to describe the constructions of tufted carpets;
  • Explain the hand-knotting method of making a carpet;
  • Describe the tufting method of making a carpet, including the machine features required to produce loop pile and cut pile constructions;
  • Briefly outline the methods of making Axminster, Wilton and face-to-face woven carpets; and
  • Discuss the advantages and disadvantages of the various production methods for machine-made wool carpets, including construction, production rate, and patterning options.

Topic 14: Wool Dyeing Principles and Techniques

The physical and chemical properties of wool vary greatly between breeds, the environment in which the wools are grown and the diet and health of the sheep. The physical properties vary in terms of fibre diameter, length and crimp whereas the chemical properties exhibit variety in terms of amino acid content. In addition, wools also vary in their base colour and have differences between the tip and root that affect both the dyestuff diffusion rate and mechanical properties. It is common to blend wools with different physical and chemical properties, and these blends may display markedly different dyeing properties. Therefore, careful selection of dyestuffs and auxiliary dyeing chemicals is important if the desired, stable colour is to be achieved on completion of the dyeing process.

On completion of this topic you should be able to:

  • Compare the features of the four main classes of dyestuff used for dyeing wool;
  • Explain the roles of dyeing auxiliaries and assistants;
  • Describe what occurs at the molecular level during the five phases in the dyeing process;
  • List the factors that affect the effectiveness of dyeing and explain the reasons; and
  • Describe the machines used for the dyeing of loose fibre, tops, yarns and fabrics, and compare their advantages and disadvantages.

Topic 15: Principles of Wool Fabric Finishing

The objective of wool fabric finishing is to develop the desired properties in woollen and worsted fabrics that meet the specified end use requirements of consumers. Finishing is a sequence of dry and wet processes that is carried out in a logical order. This lecture provides an overview of the principles of wool fabric finishing. The topic of wool fabric finishing is a very extensive one, and therefore can only be dealt with quite briefly here.

On completion of this topic you should be able to:

  • Explain the various types of dimensions change that can occur in fabrics;
  • Describe the finishing methods used to remove contaminants from greige state wool fabrics;
  • Outline the finishing methods used to stabilise the dimensions of wool fabrics;
  • Describe the methods used for drying wool fabrics; and
  • Describe the finishing processes employed to modify the handle and appearance of wool fabrics.

Topic 16: Effect of Fibre Properties on Processing Greasy Wool into Worsted Yarn

This topic describes the effect of fibre properties on performance in the conversion of greasy wool through to top, and into worsted yarn. The spinner’s requirements drive the specification of top properties and ultimately what wool is purchased and, together with supply and demand, the price relativities. The potential performance in spinning and the yarn properties are determined or limited by the fibre properties and so it is possible to predict expected performance and establish a firm basis for the relative importance of fibre properties.

On completion of this topic you should be able to:

  • explain how and why greasy wool fibre properties affect topmaking;
  • explain how and why top properties affect yarn properties and spinning performance;
  • explain of the key drivers of the specifications for tops and greasy fibres; and
  • describe the relative importance of fibre properties in early stage processing.