Wool Resilience

The Stretch and Recovery Properties

Wool is also extremely resilient and highly extensible, which essentially means you can stretch it a third of its length, or two-thirds when wet, and it’ll recover to its original shape. Despite over a century of effort, not a single manmade fiber yet possesses all those amazing qualities.

The natural length of a fiber varies, depending on the sheep breed and the frequency of shearing – here we are assuming the standard cycle of twice a year. A general rule is: the shorter the fibers, the softer they will be against the skin. But as with all good things, there is a drawback in terms of wearability. Since abrasion attracts the ends of fiber, working them loose from the fabric until they form pills, the more fiber ends you have per 2.5 cm (1 inch) of yarn, the greater the number of pills you may get. This is why even the best Merino yarn may eventually pill.

One of the most important things to know about wool is that it is hygroscopic, which is a great trait for clothing. Hygroscopicity means that the fiber can absorb up to 30 percent of its weight in moisture while still feeling warm and dry against your skin. This helps the fabric breathe, as it can readily absorb and release moisture to maintain a steady level of comfort against your skin, no matter how cold or damp the external weather may be.

Another advantage of wool is that it is naturally flame-retardant, making it a favourite material for fireman’s blankets and industrial fabrics in public buildings. When exposed to flame, wool extinguishes itself without a peep. Additionally, the constant level of moisture in the fiber prevents wool from conducting static electricity, which not only causes annoying shocks but also attracts fine dirt and dust particles deep into your garment.

Hygroscopicity and Flame Retardancy

Wool advantages

Eliminating Scales for Improved Qualities

Superwash Wool

Instead of trying to breed sheep that produce scale-free fibers, textile scientists have tried to eliminate the scales from existing fibers. This led to the creation of superwash wool, which involves removing the scales through various processes. Early methods involved burning the scales off at a high temperature, but this proved too harsh for the fibers.

Today’s superwash wool may also be treated with enzymes that eat away the scales. As a result, superwash wool tends to have a denser hand and more lustrous appearance, although the altered surface can impact the fiber’s ability to take dye. It’s important to check yarns for colorfastness.

Sheep are generally shorn twice a year – once in the spring and once in the fall. Depending on the animal and the frequency of the shearing, the fiber length (often called staple length) averages anywhere from 5 cm in the fine wools to 50 cm in the longwools.

Sheep wool

The mass of fiber shorn from a sheep is called a fleece, and it contains everything that was on the sheep at the moment it was shorn – including vegetable matter, dirt, and lanolin, a greasy substance that is secreted from the sheep’s sebaceous glands. Lanolin helps repel water from the sheep’s coat (which can be especially handy for sheep that live in wet climates) and may also help protect the sheep’s skin from infection.

Finer fiber fleeces tend to have far more lanolin (sometimes 35 percent of the overall fleece weight), while some Shetlands and Icelandics are so clean that they can be spun “in the grease”, that is, without any washing whatsoever.

Sheep Fleece

From fleece to fiber

Commercial Wool

Fiber Blends and Selection Criteria

With just a few exceptions, most commercial wool yarns are made from a blend of fibers that the manufacturer has chosen for their specific crimp, loft, fineness, staple length, strength, warmth, resiliency, and, perhaps most importantly, cost and availability. Rarely do you get a skein that’s labeled 100 percent of one specific sheep breed – the exception being wool whose breed name enhances its price and marketability, such as Merino, Icelandic, Shetland, or Rambouillet.

Yarn manufacturers normally purchase their wool from brokers who use fiber diameter (or micron count), staple length, and cleanliness as their selection criteria.

 The only exception here seems to the superwash Merino sock yarns that is so prevalent with 

 hand-dyers these days.  Perhaps the most important drawback of the superwash process, however, has to do with stretching. Since the fibers lack the scales that normally help hold everything together, some superwash wools can stretch dramatically with washing.

Your best course of action is to buy a single skein of yarn and knit a sizable swatch with it. Wash the swatch and let it hang dry. Hanging handknits is normally a no-no, but in this case we want to induce stretching to see how far it goes.

If you find a superwash wool you like, you will only need to swatch it once to be sure. Then you can return to it again and again.

Natural Fibers

Discover wool’s versatility