Section 2.74: Luster in Suri

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Luster in Suri

When we open a Suri’s fleece or watch a Suri move through a sunlit field, the luster we perceive is the result of light reflecting off the unique structure of Suri fiber. Luster is the key characteristic that distinguishes the rare, elite Suri fiber from most other natural fibers.

Suri luster results primarily because of the length, evenness, and uniformity of the individual scales on each fiber shaft. Studies show that the signature sparkling glow in Suri fiber is produced by its flatter, more elliptical shape (as opposed to cylindrical), in addition to the length, evenness, and consistency of scale structure. It has also been suggested that light not only reflects from solid Suri fibers, but penetrates into medullated fibers as well, thereby adding another dimension to its luminosity.

Under a microscope, Suri fiber scales appear fewer and longer than those on Huacaya fibers. While numerous short scales may diffuse reflected light, the fewer and longer Suri scales efficiently reflect significantly more light into a concentrated area, like into your eye. Suri scales are twice the length of those of sheep wool. The larger, uninterrupted fiber surface acts more like a mirror than a prism and reflects the sun’s rays effectively and efficiently. While genetics are the biggest factor in achieving luster, a sick or underfed Suri, no matter how well it is genetically predisposed to exhibit luster, will appear chalky and dull. Environmental factors matter. Trace element deficiencies, such as iodine, can inhibit the amount of luster in a fleece.

The Suri Network Study is a work in progress that is focused on defining, analyzing, and measuring Suri Luster. The following elements are being developed, compiled, and/or explored:

  • Collection of objective baseline data that can be meaningfully connected to Suri fiber qualities, the most important of which is luster. Data collection methods will include:
  • Skin biopsies
  • Scanning electron microscope examinations
  • Amino acid analysis
  • Histograms
  • Collection of shear weight data
  • Analysis of the effects of washing, processing, and the like.
  • Exploration of how to measure luster; how luster is affected by breeding decisions and environmental factors; and how breeders can improve luster.
  • Development of a broad spectrum of alpaca fiber samples that includes all colors, in the full range of luster.
  • Development of a complete and independent luster evaluation method that can be implemented by a panel of trained alpaca judges.
  • Development of a method for performing quantitative measurements for luster in fiber samples.
  • Calibration of that automatic system under various conditions.
  • Compilation of a series of washed samples from a single fiber source.
  • Comparison of data drawn from analysis on washed samples with data drawn from analysis of unwashed samples.

Some studies suggest that the brighter or more lustrous the fleece, the softer the handle. Frequently, bright fleeces tend to have a very low curvature metric, as is the case with Suri fiber. Although, as noted previously, the decision to use a "woolen" vs. a "worsted" processing method is generally more dependant on staple length, than on crimp style, some people feel that a low curvature fiber is best suited to the "worsted" method. This is because "woolen" textiles need memory, loft, and a spring-like resistance to compression, which is generally better achieved with a higher curvature fiber. One processing method is not considered better than another; they are just different approaches, with each tending to be better suited to certain fiber characteristics, in particular fiber length. 

A point to remember is that not all textile producers are interested in producing finished products that exhibit luster or brightness, as not all end uses are compatible with shine. Furthermore, if a manufacturer wants some brightness or sheen in a particular textile, blending in a synthetic nylon or another petroleum-based product will often produce the desired result. Very little synthetic material is required to impart sheen to a finished garment. The real beauty of using natural silk to manufacture stockings or hose for women is that it makes their legs look terrific without the shine that is produced with nylon. In fact. nylon producers have gone to a lot of trouble to try to design synthetic fibers that do not have too much luster. In the synthetic world, very shiny end products are often equated to a gaudy or even a "worn out" look.

Suri fiber, on the other hand, is a natural and inherently lustrous fiber, much more akin to silk than to shiny synthetics. It is that natural luster on which Suri breeders must capitalize. When its luster is coupled with density and uniform fleece architecture, Suri fiber can really light up your world! 

A Few Points on Suri Luster:

  • Some people believe that high luster necessarily correlates to softness because fewer scales (cuticle cells) result in less drag. There is not full agreement on this, however.
  • In general, high luster and brightness tend to be exhibited by more uniform fleeces, which will tend to have a softer hand.
  • Suri fibers exhibit an elliptical shape in cross-section, as compared to the cylindrical structure of Huacaya fiber. Its elliptical shape, along with its fewer scales, results in the Suri's luster, whereas the Huacaya's cylindrical fiber shape produces the feature we label brightness.
  • The wool industry distinguishes three types of luster: silvery, silky, and vitreous. The silvery luster is found in the finest Merino wools, that exhibit a high degree of crimp. The silky luster is present in the long staples of British breeds, like the Lincoln and Leicester. The vitreous luster is found in Mohair and other goat fibers. Von Vergen studies of alpaca fleece mention that Suri fleece exhibits a silky luster, while Huacaya fleece has a silvery luster.
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