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Wool Measurements

Posted 2/19/2012 6:56pm by Eugene Wyatt.

A 17 Micron Saxon Merino Ram

Wool is measured by its average fiber diameter (AFD) expressed in microns (one micron equals one millionth of a meter) and by its yield, which is the percentage of clean wool that remains after vegetable matter and grease have been washed out.

We always shear the first Monday in March, about two weeks before lambing begins. This year that Monday falls on March 5 with lambing beginning on or about March 23; that date is dependent on when we put the rams in with the ewes. Gestation in sheep takes five months.  

Shearing the ewe before lambing makes birthing easier for all involved: the ewe, the lamb and the shepherd.  The ewe can better mother her lamb, the lamb can better find the teat and the shepherd can better see how the mother and newborn are doing.

Shearing in late pregnancy: there is no danger of premature birth or of losing the lamb to an abortion (the sheep term for miscarriage) as there would be if the ewe were shorn in the early months of gestation. We schedule no handling of bred ewes in the first 3 months of pregnancy, no feet trimming, no deworming and no vaccinating for fear the ewe will lose her lamb. 

Last year at shearing we separated the lamb fleece (wool from sheep born a year ago) from the fleece of the older sheep by sorting the sheep into two age groups before shearing them.  After shearing I ended up with 1 bale of lamb's grease fleece and 4 bales of the grease fleece from older sheep.  The bales weigh about 600 lb.; they are shipped to the scourer for washing.  The yield is simply determined by weighing the grease wool before and the clean wool after scouring. For micron testing, core samples of the clean bales of wool are taken and sent to a wool lab for laser analysis.  I can have the wool micron tested at Texas A&M or privately, as I did, at Yocom-McColl Testing Laboratories.

The micron test results came back Friday:

The AFD of lamb's wool, which is 100% Saxon Merino, measured 17.4 microns with a yield of 63.7%. This is an Ultrafine wool.  

The sample was from about 150 fleeces; some lambs had finer wool (sub 16 micron) and others had coarser wool. Green Mountain will spin it into yarn in March or April depending on their schedule. I suspect they've never spun a wool as fine as this.

The Superfine wool from the older sheep (also 100% Saxon Merino), which is coarser because older, had an AFD of 18.7 microns with a yield of 65.3% which is a record or a near-record yield in the United States. American sheep usually yield less than 50%.

For your inspection: the Sirolan Laserscan Micron Test Report from Yocom-McColl on the core samples of my Saxon Merino lamb's wool.