Knitwear Design 101 | Fabrication, part 1

Image of my hand holding a mauve lacy sweater, knitted in a wool, silk and mohair blend.

Knit and crochet designers have several duties when it comes to fabrication. As well as considering the overall shape and silhouette of a garment, there comes the question of:

Fibre type
Yarn construction
Fabric construction
Appropriate construction techniques
Appropriate finishing techniques

This post focuses on fibre type and touches on yarn construction; fabric construction, construction techniques and finishing will follow.

Fibre type

This is probably the most easily understood of the five questions. Broadly speaking, there are three main fibre types:

Cellulosic
Protein
Synthetic

Skeins of yarn in various blends, including alpaca, cotton, wool and silk, constructions and colours. The palette is a soft combination of baby blue pink, dove grey and speckles.

Cellulosic fibres include anything derived from a plant or part of a plant, whether the stem (linen, ramie, hemp) seed casing (cotton), leaf (sisal, abaca) or husk (coir, or coconut fibre). Such fibres can be classified as natural if the production processes do not involve chemically altering the molecular composition; mechanical processes such as pounding, spinning, combing or crushing are allowed. Natural cellulosic fibres are breathable, cool next to the skin, quick-drying, but few are elastic.

Protein fibres include animal hair; typically, wool, cashmere, alpaca, yak, vicuna, angora, mohair and llama are well known, but silk, spun by silkworms as they transition from caterpillars to larvae, is another type of protein. Protein fibres are typically shorter than cellulose fibres, but silk is a notable exception; it is a long, continuous filament, NOT a fibre. Protein fibres or filaments are beautifully responsive to dye, warm next to the skin, breathable, and fairly elastic.

Synthetic fibres, on one hand, include petroleum derivatives such as polyester and acrylic, but on the other hand, also includes fibres in the rayon family. Viscose, cupro, and modal are obtained from soft woods such as beech, but are classified as either regenerated cellulose or semi-synthetic due to the chemical production processes involved. You can read about those in the references below, but in short: sodium hydroxide (aka caustic soda or lye) is added to cellulose, which then breaks down into liquid form; the resultant liquid is forced through spinnerets and converted back into solid fibres by dint of an acid bath; this bath can contain 10-15% sulphuric acid. This process is also known as wet spinning. Technically, these fibres are filaments; they are completely continuous, but are often referred to as fibres for simplicity’s sake.

At the time of writing, lyocell produced by Lenzing in Austria (Tencel®) is the only rayon that does not produce toxic by-products and involves a closed loop production cycle, i.e., all by-products are environmentally safe and can be reused. Properties of rayons can vary due to the variety of production processes available, but it is normally fair to assume that a rayon will share some qualities with its parent cellulose fibre. For example, they are normally weaker when wet; like cotton, they absorb a lot of water; and like linen, repeated erosion or folding in the same spot can cause weakening or permanent damage to the delicate threads.

A Designer’s Duty

An excerpt from my bullet journal, which shows part of a reference or checklist I use for writing pattern listings.

There’s no harm in having favourite fibres, but anyone designing clothes is charged with knowing something about fibres and fabric; they are the foundation of your design, the point at which it becomes matter as opposed to something in your mind, and another important connection with the knitters making your designs. As a designer, it is also my responsibility to design garments and accessories that will suit or can be interpreted in more than one type of fibre; whether that is a pullover that works equally well in cotton or wool, or a sweater that was inspired by the drape of alpaca that could easily be worked up in a linen or Tencel®.

I have no way of knowing what will suit the wearers of my designs, but I can certainly say something about the qualities of the fibre I chose and how that makes the design successful. This also makes yarn substitution easier; apart from cost, I will stick my neck out and say that fabrication is one of the top three reasons why knitters or crocheters will deviate from the specified yarn. Nobody in a tropical climate will want to wear alpaca, but if a resident knitter wants to knit your design, it is very reasonable to give them some advice about what they could use instead. This doesn’t involve throwing your yarn sponsor under the bus, or undermining their support in any way; it is a realistic assessment of the situation.

For numerous reasons, it will not be possible for everyone to knit your design in the sample yarn – and that truth can be acknowledged without hurting anyone. Further, some skins cannot tolerate short fibres such as mohair or angora, or some wools. It is impossible to please everybody, and I promise that I don’t attempt to, but human consideration and empathy goes a long way. If you have chosen mohair and silk for a shawl, it is also worth knitting a swatch in a different laceweight for comparison. It will benefit you as a designer, and you can share it with prospective buyers of your pattern. They may not ask you directly about yarn substitution, but they will appreciate seeing different yarns worked up in the same stitch pattern.

Fibre Staple and Yarn Construction

Images of aran weight yarn in autumnal colours. All these yarns are 100% wool.

The staple of a fibre determines how long it is, and consequently the cost and perceived quality. I’m no spinner – please ask your local or favourite spinner if you have one, they’ll be glad to tell you what I don’t know! 😉 – but fibres with longer staples are sometimes viewed more favourably, or used as a selling point. This is partly because shorter fibres are more difficult or time-consuming to spin, and partly because long-staple fibres have a softer handle. Two examples of long-staple fibres are merino wool and pima cotton; short(er)-staple fibres include alpaca and angora. Consequently, short-staple fibres are often combined with longer staple ones to confer more stability and keep costs down.

Of course, none of this necessarily affects the quality of the yarn or thread produced. This is where we have to give thanks to the spinners and producers who produce beautiful and responsible goods using their considerable depth of knowledge. I know I’m always hunting around for new and interesting blends of yarn for my designs. I certainly have my favourite fibres and blends, but I will bench them if a design or stitch texture calls for it. Knitting and crochet takes place worldwide, and it usually isn’t very long before one of your patterns is bought by someone thousands of miles away.

At this point I will completely cop out of yarn construction: yarn can be plied, chainette, or roving, but I’m too far out of my comfort zone discussing the details of how those are created. Again, I recommend talking to someone who has a clue (read: practical experience – I have none), but I can say that, like fibre type, this also has a bearing on how your yarn behaves. Some types of yarn construction can accentuate or detract from the fibre qualities, and the effects of this can be fascinating. The only way to find out about this is to test it out, and happily, fabric construction is well within my lane! More about that in the next Knitwear Design 101 post.

References

https://www.sciencedirect.com/topics/engineering/lyocell-fiber

https://www.sciencedirect.com/topics/engineering/coconut-fiber

https://www.sciencedirect.com/topics/materials-science/rayon