Micron Count System

As a relatively new spinner, I had to do a bit of research on this concept of ‘microns’ as it relates to wool softness. I’ve seen how some on Ravelry use micron as a determining factor for their fleeces, wools, etc. So, I did a bit of research on the subject.

In general, the Micron system uses the measurement of a micron (1 millionth of a meter or 1/25,000 of an inch) to determine how the type of wool (either ‘fine’ or ‘coarse’). However, the “micron” count does not necessarily mean is of good quality. The micron count of a lot or fleece of wool uses the “average micron count”. But, apparently, this count can be deceptive.

For example, if you have a lot of wool, where
• 50% of the fiber = 35 microns
• 50% of the wool = 15 microns,
• the average micron count for that LOT is 25 microns.
• So, you’d have a lot that’s a mixture of both “coarse” and “fine” wool.

Consequently, the additional measurement of the amount of variation in fiber diameter (the Standard Deviation Column) can give you a better insight to the quality of wool. So a fleece or lot of wool with its individual fibers closer in diameter could be considered a more “quality” wool [1]

Type of Wool	Micron System	Maximum Standard deviation (microns)
Fine	Under 17.70	3.59
Fine	17.70 - 19.14	4.09
Fine	19.15 - 20.59	4.59
Fine	20.60 - 22.04	5.19
Medium	22.05 - 23.49	5.89
Medium	23.50 - 24.94	6.49
Medium	24.95 - 26.39	7.09
Medium	26.40 - 27.84	7.59
Medium	27.85 - 29.29	8.19
Medium	29.30 - 30.99	8.69
Coarse	31.00 - 32.69	9.09
Coarse	32.70 - 34.39	9.59
Coarse	34.00 - 36.19	10.09
Very Coarse	36.20 - 38.09	10.69
Very Coarse	38.10 - 40.20	11.19
Very Coarse	Over 40.20

There are no hard-and-fast rules on how different types wools should be used, but there is a general guideline: [2]

• 16-19 Fine worseted & intimate wear
• 19-23 Apparel, outerwear, quilt batting / felts
• 23-28 Sweaters, light upholstery coatings, fiberfill
• 28-32 Upholstery, tapestries, some carpets
• 32-38+ Carpets, industrial use.

Of course, from reading various articles, going micron mad is probably not the best way to raise animals or determine the best wool needed. There’s the role of “crimp” in determining uniformity or density in wool, and is a factor in selecting a fleece. But that’s another topic for another time.

So conclusion? Micron count should be used as a guidelines for merely determining “softness” of a given wool or as a consideration when selecting a fleece or wool. It shouldn’t be the end-all-be-all of the decision process.


[1] http://msuextension.org/publications/AgandNaturalResources/MT198380AG.pdf
[2] From the Navajo Sheep Project: http://navajosheepproject.com/images/pdf/wool/woolgrading.pdf