Judging Wool Quality

If you have notions about buying, selling, or making things from it, knowing how the pros assess wool quality is helpful.

| March/April 1983

  • wool quality - scribbled sheep
    Wool quality is a function of fiber length, diameter, and density, which vary with the breed, size, and health of the sheep it comes from.
    Illustration by Fotolia/puckillustrations

  • wool quality - scribbled sheep

In the wild, members of the sheep family have two distinctly different coats: an outer one consisting of long, coarse hair (known as kemp) that protects the animal from the elements, and an undercoat (called wool) which is soft and curly and keeps the creature warm. Domestication and selective breeding have eliminated most of the long hairs (although a few breeds, such as the Scottish Blackface, still sport abundant kemp), and today's sheep are covered almost exclusively with true wool. This remarkable natural fiber is distinguished by its fineness and scaly surface (which helps the strands hold together when spun or felted), its crimped or wavy appearance, its elasticity, its strength and durability, its effectiveness as an insulator, and its ability to absorb water and accept dyes.

In general, there are two wool classes: "apparel" and "carpet." Fleece of the former type is finer and can be spun into a yarn suitable for clothing fabrics, while the latter is coarser and lends itself best to use in floor coverings or wall hangings.

Factors to Check Out

When you evaluate wool quality, there are several things to look for. The first and perhaps most important consideration is its weight.

This will depend upon the length, diameter, and density of the wool fibers, and these in turn vary with the breed, size, and health of the sheep. At the same time, the amount of extraneous material in the untreated fleece (which may account for half to three-quarters of its initial weight) must be determined.

Wool length can be anywhere from 1 to 20 inches. To check a fleece for length, gently part the fibers, hold them down smoothly with the flat of your hand, and measure from the skin out. Examine several areas, as the length varies on different parts of the animal's body. The longest fibers are found in the britch (the area down the outside of the hind leg) ... the next longest on the sheep's side ... and the shortest on the head.

The diameter of the wool fibers—which usually ranges between 0. 0007 and 0.002 inches, or between 17 and 40 microns is difficult to measure without special equipment, although visual examination and touch can give you some idea of the fineness of the individual strands. An easier way to determine quality is to look at the crimp (the little S-shapes) in the strands. Crimps vary from 5 to 36 per inch: The more crimps, the finer the wool. The finer the wool, the higher the quality. In fact, the character of a fleece is judged by the evenness, distinctiveness, overall uniformity, and number of crimps in the fibers.

3/28/2010 5:38:21 PM

great article but where is the chart that it talks about at the end

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