These fiber notes are still evolving, as I gain experience with various fibers. The inspiration for this page is a desire to learn more about the fibers available to me, and an interest in introducing these qualities to others who are equally curious about the possibilities for spinning that surround them.
The Fibers: Mechanical Properties and Traits
The mechanical properties of the fiber used to make a yarn are an important factor in the results of any spinning session. Each individual strand is a three-dimensional object, and its thickness, length and shape all add to the yarn’s strength, luster and hand. We’re going to summarize the basic properties here.
Wool: the ultimate example of a non-straight fiber. It has kinks and waves, and even the tightest spun thread will still have plenty of space for air pockets, which is why even wet wool will help keep you warmer. If you look at the fiber under a microscope, you can see the small scales covering it. Those scales hold the fibers together, and also help with the felting and fulling of the wool. (Wool loves to cling to itself, and will try to do so at almost any opportunity.) The fiber length varies, depending on the breed of sheep, but usually range at least 3 to 6 inches or longer.
Wool is very stretchy, elastic and resilient — it is possible, by blocking (i.e. applying heat, moisture and tension), to reshape the fibers down to the molecular level. If blocking is done properly, it will not degrade the fibers to any great extent and is even reversible, if not done to extremes. Wool’s resilience is also the reason it does not hold wrinkles for long.
Conducts heat poorly — a good insulator. (Wool is “warm”.)
The most absorbent fiber — holds up to 30% of its weight in moisture, without feeling wet.
Fulls and felts easily, and lends itself to having a nap raised.
The weakest fiber, and weaker when it gets wet.
Dyes well, and resists mild and dilute acids. (On the other hand, it is destroyed by alkaline substances, and is attacked by larvae of moths and carpet beetles.)
Flax: essentially straight, although its fiber structure shows a definite left-hand (S-twist) spiral. (Other bast — i.e. plant-based — fibers show a right-hand, Z-twist spiral, which has been used to help identify them.) The singles are traditionally spun counterclockwise, when other fibers are usually spun clockwise. Through a microscope, you can see the cellular structure as small bumps, where the end of one cell overlaps the next cell. These cells are held together by a gummy substance, pectin, allowing a flax fiber to be 18” to 24” long, even though the cells themselves are only 1/4” to 2 1/2” long.
Flax is non-stretching and inelastic — it doesn’t easily return to its original shape after being deformed by tension. (This is why linen wrinkles easily, and stays wrinkled until ironed.) Being 70% cellulose, and 30% lignin, pectin, gums, etc., it is a stiff fiber that doesn’t bend well, due to the lignin supporting the cells, so it cannot produce a stretchable fabric. As it ages, the non-cellulose materials within the fibers are gradually removed, leaving the structures much more flexible.
Conducts heat better than wool or silk. Linen is “cooler to the touch”.
Readily absorbs moisture, and is stronger when wet. Also the fastest drying of the four fiber groups.
Unharmed by strong alkalis. Long exposure to sunlight, though, does bleach it, and weaken it somewhat.
Strongest of the four fibers.
Silk: an extruded fiber, this is the one closest to actually being straight. It is also the smoothest. When examined under a microscope, it can be seen to be one long glassy rod. Since it is extruded from the caterpillar as a viscous protein fluid, instead of growing with the animal (wool, hair) or plant (flax, cotton), the difference in structure is to be expected. This filament is coated with sericin, a glue that holds the cocoon together for the caterpillar’s transformation into a moth.
It may not be as elastic or as resilient as wool, but silk has the best combination of tensile strength, stretch and resilience. In fact, silk can be stretched out of shape and not recover, which can be a problem. Care must be taken with wet silk, that its shape not be altered while drying.
Conducts heat poorly — a good insulator. (Silk is warm to the touch.)
Does not absorb large amounts of moisture, but dries quickly.
Weakens somewhat when wet.
Dyes very well — beautiful, vibrant colors.
Easily attacked by weak inorganic acids, oxygen in the atmosphere, and by carpet beetle larvae.
Sunlight is not good for silk.
Static electricity build-up can occur, especially during periods of low humidity and cooler temperatures.
Cotton: each fiber is a single cell — when alive, these cells are hollow tubes. Once harvested, the cellular material dries and the cells collapse into flattened tubes which twist and turn constantly. The resulting convolutions provide friction and keep the fibers from compacting, allowing room for air pockets to help provide warmth.
Cotton is another fiber that doesn’t stretch easily and is non-elastic. It is much more flexible than flax/linen, though, so it is possible to make stretchy fabrics from cotton. This is due more to the overall fabric structure (e.g. knitting) and yarn twist than the fiber itself.
Absorbs moisture quickly, but doesn’t dry as quickly as flax.
Stronger when wet.
Resists alkali damage, but even dilute acids will easily attack it.
Sunlight slowly degrades cotton, certain dyestuffs can accelerate this degradation.
Not attacked by moths or beetles, but will mildew easily if not stored in clean, dry conditions.
There are many characteristics that affect the spinning qualities of any fiber. Consider this to be just a starting point for choosing which fiber you want to use for your spinning projects.