Micron is the measure of fibre diameter of wool (one micron is one one-thousandth of a millimetre).
Deviation is a statistic that summarises the
way diameter results from individual fibres are spread around the mean fibre diameter. It measures the absolute distribution of fibre diameter either side of the Mean and
is expressed in microns. Sixty eight percent (68%) of fibres fall within a range
one Standard Deviation either side of the Mean, and 95% of fibres fall within a range two
Standard Deviations either side of the Mean. For example, a wool with a Mean Fibre Diameter of
20Ám and a Standard Deviation of 4Ám will have 68% of fibre snippets between 16.0Ám and
24.0Ám and 95% of fibre snippets between 12.0Ám and 28.0Ám.
of Variation is a measure of
the relative distribution of fibre diameter and is expressed as a percentage (%). It is calculated by
expressing the standard deviation as a percentage of the Mean. For example, a wool with a Mean
Fibre Diameter of 20Ám and a Standard Deviation of 4Ám will have a Coefficient of
Variation of (4.0¸20.0) x 100=20%.
Factor is expressed as a percentage and is
defined as the proportion of fibres which have a diameter of less than 30Ám. Research
has shown that wools with a comfort factor of 95% or greater (i.e. less than 5% of
fibres greater than 30Ám) can be comfortably worn against the skin. A wool with a comfort factor of 100% contains no fibres greater than 30Ám.
Fineness is expressed in microns and provides
an estimate of the performance of the wool when it is spun into yarn. The spinning fineness is calculated from the measured Mean Fibre Diameter and the measured
Coefficient of Variation of Fibre Diameter. The spinning fineness is the same as the Fibre
Diameter when the Coefficient of Variation (CV) is 24%. Wools with a CV of less than 24%
will have a spinning fineness less than the Fibre Diameter.
© The Australian Association
of Stud Merino Breeders Limited
The Australian Merino Centre
Level 2, RAS Administration Building
1 Showground Road
Sydney Olympic Park NSW 2127
Telephone: 02 9763 2744
Fax: 02 9763 1878