Advanced Topics in Wool

It’s back to school time! In today’s session we will cover the finer points of wool – and why all cloth is not created equal.


The quality of the raw wool is the single most important factor in the outcome of the finished cloth. Wool is judged in 5 key areas:

  1. Diameter. The smaller the diameter of the raw wool fibers, the more luxurious the eventual cloth. Wool diameter is expressed via the “Super” scale. On the “Super” scale, cloth made from finer diameter wool has a higher number. For example, a “Super 100’s” cloth is made from wool with a diameter of about 18.5 microns; compare this to an ultra high-end “Super 220’s” cloth with a diameter of just 12.5 microns. (For perspective, human hair has a diameter of 60 – 70 microns!) Just remember: the higher the “Super” number, the finer the wool fibers.
  2. Length. The longer the raw wool fibers, the better. Longer fibers resist “pilling” and lead to a more consistent cloth. The ideal length for a suit cloth is five to seven inches.
  3. Strength. A strong fiber ultimately weaves into a strong and enduring cloth; a weak fiber will result in a poor cloth. Wool is measured for its tensile strength.
  4. Crimp. Crimp is a measure of the natural elasticity or memory of the fibers. Wool fibers must have a certain degree of memory in order for a finished garment to recover between wearings and maintain its shape.
  5. Purity. Raw wool must be carefully scoured (cleaned) to remove all impurities and organic materials that may have become trapped prior to shearing. Even the slightest extraneous material will result in unwanted irregularities in the cloth.



Once the raw wool has been selected, scoured, and dried with hot air, it is “carded”. Carding passes the clean, dry wool fibers over multiple closely-set rollers, each covered with as many as 800 tiny metal wires per square inch. The carding process disentangles the scoured wool and shapes it into a twistless, rope-like form. After carding, most raw wool destined for use in fine garments is combed. Combing removes shorter fibers and makes the remaining longer fibers lie parallel. Wool processed in this way is referred to as “worsted wool”. The term “worsted” comes from the English village of Worstead, where expert cloth workers first began combing wool by hand in the 14th century. (Some fine wool is carded, but not combed. Uncombed wool is referred to as “woolen” and is typically hairier in its finished appearance. “Woolens” are used mostly in sport coat cloths. Thus, “worsted” is combed and “woolen” is not.)


The wool is now ready for spinning. Spinning twists wool fibers into yarn. Balance is critical here: more twists per inch will make a yarn more durable, but at the expense of the softness of “hand” or feel; fewer twists per inch will give a softer hand, but may leave the cloth too weak and delicate. Two ply yarns, where two single spun yarns are twisted together, generally yield the best combination of strength, softness, and ultimately, performance in the finished cloth.


The weaving process interlaces “warp” yarns (length) with “weft” yarns (width) to create the unfinished cloth. Different warp yarns are lifted in successive passes of the weft yarns. The order in which the warp yarns are lifted will determine the structure of the cloth; differences in yarn colors will determine the pattern. Plain weave is the most basic structure and is the weave of lightweight tropical cloths. Twill weaves are used for the majority of medium to heavy weight cloths. Achieving the appropriate tightness of the interlaced yarns is critical to the success of weaving.


The woven cloth is now ready for finishing.

The cloth is first washed in warm water. Washing softens the wool fibers and relaxes the strains and tensions created during the weaving process, thereby minimizing the potential for future relaxation (shrinkage) when a garment is dry cleaned or pressed. Washing also removes any residual oils and additives that may have been used in manufacturing.

Next the cloth is dried full width. Then the fibers on the surface of the fabric are raised by brushing rollers and cropped or shaved to the required length for the specific finish desired.

Finally the cloth is pressed and inspected.

It is the finishing process, whether it be for a closely cropped clear cut worsted tropical, a semi milled twill, or a rich and lustrous flannel, that gives the cloth its final optimized appearance and hand. The finished cloth is ready for use in fine garments.



High quality garments made from fine wool are generally low maintenance, provided they are rested at least a week between wearings. Occasional professional dry cleaning is recommended when garments become soiled. Excessive cleaning will dry out the cloth, make it feel less luxurious and ultimately shorten the life of the garment. If a garment is just wrinkled, have it professionally pressed. Don’t fall for the argument that it only costs a little more to have it cleaned – “cleaning” a garment that does not need cleaning simply ages the cloth. However, dry cleaning before seasonal storage is recommended. This will discourage moth damage and ensure that your garments are ready for the next season. Storage in a cedar closet or garment bags provides additional protection for your fine wool clothing.

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