Section 2.77: Alpaca Fiber Strength

Alpaca are renowned for producing the world’s most sustainable luxury fiber. Alpaca Fiber can be eco-friendly, softer than cashmere, and warm as polar bear fleece.

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Alpaca Fiber Strength

A strong fiber makes a strong thread and, in turn, produces a strong garment that will wear well. Fiber strength has two measureable components: tensile strength and shear strength. Alpaca fiber is naturally strong in terms of both components. 

Holes in socks are caused by failure of shear strength, due to repeated pressure applied perpendicular to the fiber. Well-made alpaca socks are less likely to develop holes because alpaca fiber has inherently high shear strength. Holes in suits, dresses, and similar garments are usually caused by failures in tensile strength, where the force applied is parallel to the fiber. Again, properly processed alpaca fiber, that includes no short or damaged fibers, will tend to resist these wear and tear issues more than most other natural fibers.

As a result of its natural strength and durability, alpaca fiber may be spun lightly to produce end products that are lightweight, but nonetheless durable. The natural strength of alpaca fiber may be compromised, however, in animals that have suffered stress, illness, or inadequate nutrition. Fiber from these animals is more likely to be "tender" and susceptible to breaking during processing. Producing strong alpaca fiber for the textile industry is dependant upon good herd management techniques. 

Staples, Staple Length, and Bundling

A staple is defined as a cluster or group of fibers that naturally grow together, as one unit, within the fleece. The number of fibers within a staple, or Suri lock, may vary significantly between animals. Staple length affects overall fiber weight, as longer staples, when compared to shorter staples of like density, diameter, and crimp style, generally will be heavier. To measure actual fiber length, crimpy fibers must be stretched to full capacity. Staple length is an attribute for which alpaca owners should selectively breed. It should be measured at each shearing and those animals not performing well should be culled from the breeding program in order to increase overall productivity of the herd.

Note: According to Dr. Jim Watts, the Huacaya alpaca has, on average, a fiber length to staple length ratio of about 1.1 to 1.0, which means fiber length is 10% greater than the staple length, with the best measured individual being about 1.35 to 1.0 (meaning fiber length is 35% greater than the staple length). 

Uniformity of fiber length is critical in processing, because mixing fibers of markedly variable lengths results in an inferior end product that tends to feel prickly to the wearer and tends also to "pill" more easily. A fabric that "pills" develops tight little balls of fiber on its surface as a result of abrasion, washing, and normal wear. Pilling occurs when short and/or weak broken fibers migrate out of the twist that was created in the fabric's yarn during processing. Although they are given a uniform twist in processing, the two lengths of fiber behave differently and, as the fabric relaxes, the shorter fibers begin to release. Uniformity in fiber length helps to prevent this. 

Many processors prefer that overall fiber length be at least 3 inches. Required fiber length is manufacturer-specific, however, and some will process shorter fibers. CanCAM, for example, uses fiber in the 1.75” to 3.75” range in their woolen process. The Alpaca Blanket Project currently uses fiber falling within the 2.0” to 5.0”range, which meets the woolen processing requirements of Pendleton Woolen Mills.

The longest fibers are generally processed using the worsted system, which produces the finest fabrics. Less twist is required in the worsted process, which results in a softer fabric. Shorter fibers generally are processed using the woolen system and are twisted more tightly to add durability. The twist also helps to hold the shorter fibers securely together, which helps to reduce pilling. Unfortunately, the tighter twists necessary to process shorter fibers using the woolen method tend to result in fabrics that do not feel as soft as worsted fabrics.

The term bundling is often used to describe fleece that exhibits well formed, uniform, and discreet staple groups. Bundling "matchsticks," for example, describe tiny, micro-staples, which in turn cling together to form larger staples. Bundling is indicative of a dense fleece and results from the evenness of follicle size and consistency of follicle shape in the skin.

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