Fleece 101

Once, when visiting friends, Joanna happened to be working on a knitting project that she had brought along. When the visit was nearly complete one of our hosts asked, “Joanna, what have you been doing all this time?” “I’m knitting a sweater,” she replied. Our host took out his wallet, handed Joanna a twenty-dollar bill, and said “Here …  go and buy yourself a sweater.” To this day, she has neither forgotten the event nor forgiven the comment. Joanna has been knitting for more than 30 years, she has been a spinner for most of that time, and she raises wool in support of her art. There is great satisfaction in crafting your own clothes – entirely from materials that you have raised and processed. Wearing a sweater, hat, or perhaps a pair of socks that once grazed your back pasture is quite something. Doing this has been Joanna’s passion, it has been our shared passion, for nearly a quarter century.

We started shearing the flock this week … one of the yearly events that we both look forward to and dread. We look forward to harvesting new fleeces and to seeing what that crop yields; at the same time we do not relish the chaos which results and physical labor required to realize such a harvest. Because we have culled our flock intensively, the naturally colored fleeces which it now produces are of the highest quality. The subject of this post is fleece quality and how it is judged.

Fiber Diameter. Wool fibers are measured in microns (µm) (millionths of meters … one micron is equal to ~0.00004  inches) and may be identified by size classes which range from Fine (<17-22 µm) to Very Course (36-42 µm). For comparison, an average human hair may range in size from 50 – 100 µm.  Fibers taken from one of our Shetland ewes ranged from Fine (18.75 µm) to Very Course (50.0 µm); the majority however were classified as Fine and Medium. Finer wool fibers may be spun into finer yarns which may be used to produce finer, lighter, more delicate articles of clothing or fabric.

Crimp. The term crimp refers to the waviness of the wool fibers which comprise the fleece. Do you remember, from high school physics class,  the meaning of the terms wavelength, frequency, and period?  Wavelength is the distance between wave crests, frequency is the number of waves per unit time (or distance or length, in the case of wool crimp), and period is time  (or distance or length) per wave cycle. In terms of wool, good crimp translates to waves of high frequency (many per unit length) and low period (minimal distance per wave cycle). Good crimp allows for good loft, or lightness, openness, or fluffiness of the yarn which results. Yarns with lots of loft are soft and comfortable to have next to the skin.

Together, fiber diameter and crimp are important measures. Wool fibers that are finely crimped and of small diameter can be spun into finer yarns. Fine yarns attain greater lengths for any particular weight. Think of the type of yarn you’d prefer to use for undergarments as opposed to that which you’d use for a rug or window treatment.

Color. Shetland fleeces come in natural colors ranging from white to brown to black. The North American Shetland Sheepbreeders Association has identified eleven colors in all.  For more information about the taxonomy of color in these animals as well as a discussion concerning color patterning in Shetlands follow the link to NASSA.

There are other aspects of the fleece that are of more or less importance to the fiber artist depending on the particular application. Wool fibers may be described by the degree to which they show luster. Luster in this case has the same meaning as in the vernacular sense of shine, sheen or gloss. Some wool fibers have lots of luster while others do not. Shetland fleeces especially may be double-coated meaning that they are made up of two sorts of fibers – soft, relatively short, and crimpy wool fibers (which have lots of loft and little luster) and coarse, long, and straight hairs (which have lots of luster but little loft). Finally, different fleeces may be characterized by differences in staple length which is a measure of the length of the wool fibers themselves. Handspinners will know that wool of longer staple is easier to spin.

This image shows a bit of a fleece taken at shearing earlier in the week. The edge at the top is the cut edge which lay close to the animal; the tips at the bottom were exposed to the weather and are sun bleached as a result (some folks cover their sheep to prevent this – we believe it adds depth to fleece color which we appreciate).

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