Wool processing: fleece to fabric
Transcript
Fleece
Different breeds of sheep produce different types of wool, from very fine merino wool to much coarser crossbred wool. Coarser diameter wool is more suitable for heavy apparel and carpets, while finer wool is used for high-quality apparel. The key properties that determine the use of wool are its diameter and the crimp. The crimp or the waviness of the fibre is different from breed to breed. In merino, it’s very fine – about half a millimetre spacing – but the crimp in crossbred wool is several millimetres long.
Acknowledgement: 123RF Ltd
Woollen processing
Dr Errol Wood (AgResearch) Many people think that woollen is woollen, but woollen is the name given to a particular type of wool processing. It’s the simplest and shortest route. It’s the most tolerant of wool types, so you can put in both good quality wool and inferior quality wool and be confident you are going to make a decent yarn from it. In New Zealand, most of our wool is processed in this way because we are a major producer of carpet yarns, and most of the carpets you buy have gone through the woollen system. It’s a very quick route – scouring, carding, spinning and twisting – basically four steps, you’ll have a yarn ready for making into a carpet. You can make also knitwear from it – it makes very nice knitwear as well – but the yarn tends to be hairy, perhaps less strong. But a hairy look sometimes is quite desirable - a kind of rustic… a genuine wool look is what you get from woollen.
Worsted processing
Dr Errol Wood (AgResearch) The worsted system is much more fussy on the type of wools that are required. They tend to be finer because the end products are going to be high-quality apparel fabrics that want soft handle and lightness of weight, good breathability and all these other desirable consumer properties. So you’re starting with finer wool. The demands for strength and length are much more critical to get a good, fine, even yarn. The target is fine even yarn, and an uneven yarn means it’s going to have thick and thin places where it may break during processing and also will look less tidy and less attractive. So that’s why we have these extra steps which don’t feature in the woollen system but are vital to making a good worsted yarn.
Scouring
Dr Errol Wood (AgResearch) The scouring process – that’s essential, because the sheep picks up contaminants such as dirt and also releases sweat and grease much like if we didn’t wash our hair for a year, imagine what our hair would be like. Well, the sheep has that same issue, so that has to be removed, and there’s a high production washing process by a wool scour. There are wool scours scattered around New Zealand, and they handle perhaps about 5 tonnes of wool an hour in their production to produce clean scoured wool – white, free of contaminants, ready for processing.
Carding
Dr Errol Wood (AgResearch) A set of processes required to convert that tangled mass of scoured wool into a nice even smooth yarn. There are variations in the number of steps required depending whether you are making a yarn for the woollen system or a yarn for the worsted system. But irrespective of what the end product is, there is the need for the scoured wool to be opened and mixed and reorganised in a nice uniform strand. We do that through a process called carding. Carding is a big machine about 20 metres long or longer with tooth rollers that tease the fibres, open them up and produce a nice even strand for the next stage.
Gilling
Gilling is a process of aligning the wool fibres so they are parallel to one another. This is done using a coarse comb. At this stage, the sliver still contains particles of vegetable matter as well as short fibres.
Acknowledgement: University of Waikato
Combing
Dr Errol Wood (AgResearch) Combing does a kind of tidy-up process. We find there’s usually small particles of vegetable matter – seeds and leaf and twigs – picked up by the sheep. They still may be in the wool, and of course they are a no-no for the yarn, so combing removes those. It also removes the short fibres, because short fibres are hard to control in the yarn. It’s much easier for the spinner to organise longer fibres.
Drafting
Dr Errol Wood (AgResearch) The strand of fibres has to come from a fairly thick strand down to a very fine one, so there are steps that enable that to happen. We call them drafting. The drafting process enables the fibres to slip apart and become finer. Here is wool prior to making a yarn – it’s called a roving. Roving is the raw material for spinning, it’s a very uniform strand of fibres – even, straight fibres ready for spinning.
Spinning and twisting
Dr Errol Wood (AgResearch): The last step in producing yarn is what we call spinning, and the ring-spinning frame does that very efficiently. The strand is taken, it’s twisted, it’s drafted into a thinner entity and wound onto a package at high speed. And so you end up with what is called a singles yarn. The singles yarn is quite fine, relatively weak, particularly if it’s wool, so it’s common practice to combine two singles yarns together, by twisting them together to form say a two-fold yarn or higher as well. And there you have your yarn.
Fabric formation
Dr Errol Wood (AgResearch) Yarn may go in a number of directions. It may be a coarse yarn going off to make into carpets. It could be a finer yarn going into upholstery or a really fine yarn going into high-quality apparel, which may be woven or knitted. So there’s a number of different possibilities depending on the raw material you’ve started with, the nature of the fibre, the type of yarn you made depending on whether its woollen or worsted and the type of end product that’s required. And so we reach the end of the process with one of those fabrics being formed, either a tufted carpet, a woven carpet, a woven fabric or a knitted fabric.
Woven apparel, carpets and upholstery
Yarns from both the woollen and worsted systems can be woven into apparel, carpets and upholstery. Worsted yarns produce finer, higher-quality fabrics.
Acknowledgement: University of Waikato
Knitwear
Yarns from both the woollen and worsted systems can be knitted into garments. Worsted yarns produce finer, smoother fabrics.
Acknowledgement: NEC wool fabric evening dress designed by New Zealand fashion designer Sera Lilly, courtesy of AgResearch
Tufted carpets
Woollen yarns may be made into carpets by tufting. In this technique, yarns are stitched through a backing fabric to create loops. The loops are either cut or left as loops, depending on the finish required. The base is then sealed with an adhesive.
Acknowledgement: AgResearch
