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Grading of Wool

Wool fiber, Wool fabric

Certain qualities such as fineness, length, color, and appearance determine the end use and value of wool. Fineness largely determines whether the wool is used in a suit, sweater, blanket or in a pair of socks.

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Why Grade

Certain qualities such as fineness, length, color, and appearance determine the end use and value of wool. Fineness the fiber diameter, or grade, and its distribution is one of the most important of these quality factors. Fineness largely determines whether the wool is used in a suit, sweater, blanket or in a pair of socks.

In general, grade refers to the average diameter or thickness of the fibers. Three systems of wool grading are commonly used in the United States: American or Blood system; the English or Spinning Count system; and the Micron system. All three systems are measures of average fiber diameter and can be related to each other. In actual practice, they are used interchangeably.

Major Wool grading systems

Wool grading

The American or Blood System

The American system of grading wool was developed in the early 1800s when the native coarse-wooled sheep were being bred to fine wooled Merino rams imported from Spain. It assumes that the offspring of the cross would have fleeces which were intermediate in fineness between the two parents. The wool grade is defined as the percentage of Merino blood carried by the sheep that typically would produce a particular fineness of wool. The grade or fiber diameter came to be expressed as fine, 1/2-blood, 3/8-blood, 1/4-blood, low 1/4-blood, common and braid. Today, these terms are not as exact as the trade would prefer, and the spread within a grade is too broad to suit the purposes of wool processors.

The English or Spinning Count System

The English system of grading wool provides narrower ranges and a more exact nomenclature than the American system. It uses a measurement called the “spinning count” and is based on the number of “hanks” of yarn which could be spun from one pound of clean wool on the equipment available at the time the system was developed.

As wool becomes finer, more hanks or yards of yarn can be spun from a pound of clean wool and the spinning count becomes larger. In theory, one pound of clean 62s spinning count wool could produce 62 hanks or 104,160 feet of yarn. (A hank of yarn is 560 yards in length.) Although wool is seldom spun to its maximum count, there is a limit to the number of fibers which will hold together in a yarn. The English or Spinning Count system of grading wool provides a numerical designation of fineness. English or Spinning Count grades of wool commonly used in the United States today are the 80s, 70s, 64s, 62s, 60s, 58s, 56s, 54s, 50s, 48s, 46s, 44s, 40s, and 36s.

Check out the yarn count calculator.

The Micron System

Increased emphasis on an exact and highly descriptive method of describing wool grade has produced a measuring system in which individual fibers are accurately measured. The unit of measure is the micron, which is one-millionth of a meter or 1/25,000 of an inch. Fineness is expressed as the mean fiber diameter. Eventually, this system will become the standard for describing wool in the United States.

Relationship Between the American, English and Micron Systems of Grading Wool

Type of Wool American or Blood Grade English or Spinning Count Grade Micron (range in avg. fiber diameter) Limit for Standard Deviation Maximum (microns)
Fine Fine Finer than 80s Under 17.70 3.59
Fine Fine 80s 17.7019.14 4.09
Fine Fine 70s 19.1520.59 4.59
Fine Fine 64s 20.6022.04 5.19
Medium 1/2 Blood 62s 22.0523.49 5.89
Medium 1/2 Blood 60s 23.5024.94 6.49
Medium 3/8 Blood 58s 24.9526.39 7.09
Medium 3/8 Blood 56s 26.4027.84 7.59
Medium 1/4 Blood 54s 27.8529.29 8.19
Medium 1/4 Blood 50s 29.3030.99 8.69
Coarse Low 1/4 Blood 48s 31.0032.69 9.09
Coarse Low 1/4 Blood 46s 32.7034.39 9.59
Coarse Common 44s 34.4036.19 10.09
Very Coarse Braid 40s 36.2038.09 10.69
Very Coarse Braid 36s 38.1040.20 11.19
Very Coarse Braid Coarser than 36s Over 40.20 0
1 Comment
  1. […] Sarapes from Saltillo Coahuila are usually made of cotton and wool, hand-spun with a winch. They usually use the same upholstery technique and the designs are formed […]

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