Wool Micron Counts

For us, one of the most important wool qualities that we strive for is softness. Of course, you can tell a lot just by touching the fleece, but if you want a greater understanding of your wool and its qualities, you can send fiber samples in to a lab to have them tested. We send our samples to Texas A&M, and for $3 per sample, they send us a report with 15 different metrics evaluating each sample. We just got back the results from our fiber samples, and we are very pleased. The micron average of our entire flock is 24.3.

     

Shetland wool can be highly variable. There are many breeders that are working to produce fine fleeces while some others have other, different breeding priorities. Some Shetland can be very fine (microns in the teens) and some can be very coarse (well over 30 microns). Even a single animal can have a large variation within its own fleece. The softest wool on the sheep is on its neck and it gets coarser as you go back until you get to the coarsest part, known as the britch. The britch is basically the wool on the back end and the rear legs of the sheep. Another consideration is that as sheep get older it is not uncommon for their fleece to get coarser and shorter. 

In order to get the most reliable and comparable results of micron data, fleece samples to be sent for testing should be taken from the same place on each sheep. The middle of the side at the first rib is generally considered to be the best place. This area in the center of the sheep provides the most representative sample of the entire fleece.   

   

One of the major indicators of the softness of a fleece is the average micron count, so of course, this is the first metric on our report. For comparison – 1 millimeter is equal to 1,000 micrometers. Generally, a micron count under 30 is considered soft enough to wear next to the skin (personally, I prefer a fleece that is under 25 microns). The average micron count is a good starting point, but there are several other metrics that are important to consider as well.

The coefficient of variation is the variation of the fiber diameters in a sample. Not all the wool fibers on a sheep are going to be the same diameter. A large variation in fiber diameters can have great effects on the feel of the wool even if the average micron is relatively low.  

The comfort factor or CF is the percentage of fibers that are 30 microns or less. A CF of 95% or above is supposed to mean that the fiber is comfortable to wear against your skin. Any significant number of fibers greater than 30 microns makes wool prickly. This means that it would not be good to wear against your skin. Fiber over 30 microns would probably be good to be used for a rug or some sturdy outerwear though.

Spinning fineness or SF is a measure of the “spinning quality,” this takes a couple of factors into consideration and creates a number that is more representative of what the fiber feels like. Sometimes a fleece with a 27 average micron can feel more like it is 26 microns or vice versa.

Staple length or SL is expressed in mm. This is the length of the fiber. In general, 3” is a good length to be used for spinning and maybe down to 2.5” would not be a problem either. Fiber that is too short can be hard to spin or create a weak yarn, although if you are determined enough, you certainly can spin shorter fibers.