Wool fineness refers only to the diameter of the individual wool fibers. When wool is graded (fineness determined), the intire fleece is given a grade that represents the average fineness. Grading is different than wool classing which is sorting flecces by fineness, staple length, strength, yield, color and style.
Three systems of wool grading are used in th U.S.: American Blood Grade System, Spinning Count System and Micron Systen. All three systems are used interchangeably, but the Micron system is used internationally and preferred by wool buyers and manufacturers.
The American Blood System was developed in the early 1800's; it is simply defined as a percentage the Merino Sheep genetics within a sheep. Merino (fine-wool Spanish breed) were crossed with native coarse-wooled sheep, resulting in the first cross, expressed as 1/2 blood, then 3/8 blood and 1/4 blood. American Blood Grade System no longer refers to breeding background, but is a broad description of fiber diameter. Grades of wool described by the American Blood Grade System are Fine, 1/2 Blood, 3/8 Blood, 1/4 Blood, Low 1/4 Blood, Commom and Braid.
Spinning Count System is a more technical classification of wool fineness, and was derived by the "Hanks" of yarn that can be spun from one pound of clean wool. Finer wools have more individual fibers per unit of weight. Consequently, more Hanks of yarn can be spun from fine wool than from coarse wool. A Hank is equal to 560 yards.
The Micron System is a much more precise and descriptive method of measuring average fiber diameter. Individual fiber diameters are measured in Microns (1/25,400 of an inch).
American Spinning Micron
Blood Count Diameter
_______ ________ ________
Fine finer than 80's under 17.70
80's 17.70-19.14
70's 19.15-20.59
64's 20.60-22.04
1/2 Blood 62's 22.05-23.49
60's 23.50-24.94
3/8 Blood 58's 24.95-26.39
56's 26.40-27.84
1/4 Blood 54's 27.85-29.29
50's 29.30-30.99
Low 1/4 Blood 48's 31.00-32.69
46's 32.70-34.39
Common 44's 34.40-36.19
40's 36.20-38.09
Braid 36's 38.10-40.20
