Making Sense of Microns

How fleece samples are taken

The integrity of sampling and the careful and proper selection of a sample is the most critical factor involved in fleece measurement. The samples are taken at the middle of the side of the alpaca in the “blanket” area. The sample is cut at the skin level, which is the base of the staple, and is usually two-inch square in size for lab analysis. The sample is kept in the staple configuration, which is its natural growth state. It is not brushed out, cleaned up, or folded. Quite simply, fleece samples are usually a small part of the fleece taken during shearing that is reserved for further analysis.

Understanding laserscan results – what do all these numbers mean?

When used properly, fiber testing can be a great marketing and genetic analysis tool. Objective measurement is an assessment made without the influence of personal feelings or prejudice. Most US Alpaca ranches have fiber testing done by Yocom-McColl Testing Laboratories Inc. based in Denver Colorado, which is a very well respected fiber analysis company with the latest high tech tools. Visual appraisal and fiber handling are fundamental aspects of fiber judging, but very weak appraisal methods of accurately identifying fiber diameter and other critical measurements.

Various instruments can accomplish the measurement of fibers within a micron. Because the measurements are so tiny, the difference between a sample at 20.5 microns and one at 22.5 microns is small mathematically, but critical in commercial use and pricing structure.

Based on this factor alone, fiber-testing technology gives breeders a useful tool to analyze fiber and track the progress of their selection programs. The determination of average fiber diameter helps identify the best end use for fiber and is information that mills require before making their purchasing decisions.

The ability to provide information on fiber quality places natural animal fiber producers in a stronger position to receive what their fiber is worth. Very few people buy and sell commodities without knowing everything they can about them. Information is power in the marketing world, and objective fiber assessment provides it.

The micron test is as good as the sample and the information submitted for testing. The laboratory cannot jeopardize its integrity by providing results from improperly taken samples, either by location or size. Breeders have the same interest in maintaining their reputations with high quality animals and by keeping accurate records of their overall performance.

Let’s take a look at a fictional histogram.

Histogram
	1	2	3	4	5	6	7	8
Date	Diameter (AFD)	Standard Deviation	Uniformity CV	%>30µ	CURV	Spin Fineness	Staple Length	Fleece Weight
5/24/09	17.6	4.4	22.7	1.3	40.1	17.1	4.6	7.27

1. The Average Fiber Diameter (AFD) is the average diameter of fibers from the sample, measured in microns.
2. Standard Deviation (SD) is a numerical measurement of the consistency of the sample. It is the most stable of variability measurement and is used in the computation of other fiber statistics such as the Uniformity, also known as Coefficient of Variation (CV).
3. The Coefficient of Variation (CV) is used in comparing different animals.
4. The %>30µ is useful because is shows the coarse edge that determines the final use for the fiber. It is directly related to the strength of the yarn that can be made from the fiber, as well as the feel, or “prickle factor”, of the final product.
5. Curv (Curvature) and Crimp (not measured by Alpaca Bella Fina) are closely related. Curv is the degree of curvature per 2 millimeter section of an individual fiber. Crimp is the visible crimp of the fiber, measured in waves per inch. Essentially, curvature is a micro measurement of the more visible crimp.
6. Spin Fineness is an attempt to combine the AFD and CV into an objective number. It is calculated by a standardized formula that gives a single measure of the estimated performance of the fleece when spun into yarn.
7. Staple length is the average length of the staple, from the point from which it was shorn from the animal, to the tip of the fibers.
8. The fleece weight is just that, the weight of the fleece directly after shearing, before any processing takes place.

Glossary of terms:
AFD – Average diameter of individual fibers, in microns.

Micron – One thousandth of a millimeter, or one 25,400th of an inch, often notated as µm. A single strand of human hair is around 100 microns in diameter.

Standard Deviation (SD) – Statistical measurement of the variability of a set of data. A low SD means that most points of a measured data set are close to the average. A high SD means that points of a measured data set vary widely from the average. In fleece measurement, the lower the SD, the more consistent the animal’s AFD is.

Uniformity CV – Coefficient of variation. The ratio of the SD to the mean (average). In fleece samples, this is a more refined measurement of fleece consistency. This number can more readily be used to compare fleeces from different animals because it is a ratio, where SD is only a measurement of the distribution of data from a single animal.

%>30µ – The percent of fibers sampled that measured more than 30 microns.

CURV – The average curvature of fiber, expressed as degrees per millimeter of fiber length. This is a precise measurement directly related to crimp frequency. The higher the CURV, the finer the crimp frequency.

Crimp Frequency – The natural wave that occurs in fibers, measured in waves per inch. This is one of the few fleece measurements that can be done at home, with nothing more than a ruler.

Spin Fineness – An estimate of the performance of the fleece when spun into yarn, expressed in microns. It is calculated by a normalized formula that combines the AFD and CV.

Staple Length – Average length of fibers, usually given in millimeters.

Fleece Weight – Weight of the fleece once shorn from the alpaca.