Raw wool has many impurities; vegetable matter, sand, dirt and yolk which is a mixture of suint (sweat), grease, urine stains and dung locks. The sheep's body yields many types of wool with differing strengths, thicknesses, length of staple and impurities. The raw wool (greasy) is processed into 'top'. 'Worsted top' requires strong straight and parallel fibres.
| Common Name | Part of Sheep | Style of Wool |
|---|---|---|
| Fine | Shoulder | Fine, uniform and very dense |
| Near | Sides | Fine, uniform and strong |
| Downrights | Neck | Short and irregular, lower quality |
| Choice | Back | Shorter staple, open and less strong |
| Abb | Haunches | Longer, stronger staple |
| Seconds | Belly | Short, tender, matted and dirty |
| Top-not | Head | Stiff, very coarse, rough and kempy |
| Brokes | Forelegs | Short, irregular and faulty |
| Cowtail | Hindlegs | Very strong, coarse and hairy |
| Britch | Tail | Very coarse, kempy and dirty |
| Source:[11] |
The quality of wool is determined by its fiber diameter, crimp, yield, color, and staple strength. Fiber diameter is the single most important wool characteristic determining quality and price.
Merino wool is typically 90–115 mm (3.5–4.5 in) in length and is very fine (between 12 and 24 microns).[12] The finest and most valuable wool comes from Merino hoggets. Wool taken from sheep produced for meat is typically coarser, and has fibers 40–150 mm (1.5–6 in) in length. Damage or breaks in the wool can occur if the sheep is stressed while it is growing its fleece, resulting in a thin spot where the fleece is likely to break.[13]
Wool is also separated into grades based on the measurement of the wool's diameter in microns and also its style. These grades may vary depending on the breed or purpose of the wool. For example:
| Diameter in microns | Name |
|---|---|
| < 15.5 | Ultrafine Merino[8] |
| 15.6–18.5 | Superfine Merino |
| 18.6–20 | Fine Merino[8] |
| 20.1–23 | Medium Merino |
| > 23 | Strong Merino[8] |
| Breeds | Diameter |
|---|---|
| Comeback | 21–26 microns, white, 90–180 mm (3.5–7.1 in) long |
| Fine crossbred | 27–31 microns, Corriedales, etc. |
| Medium crossbred | 32–35 microns |
| Downs | 23–34 microns, typically lacks luster and brightness. Examples, Aussiedown, Dorset Horn, Suffolk, etc.[14] |
| Coarse crossbred | >36 microns |
| Carpet wools | 35–45 microns[8] |
Any wool finer than 25 microns can be used for garments, while coarser grades are used for outerwear or rugs. The finer the wool, the softer it is, while coarser grades are more durable and less prone to pilling.
The finest Australian and New Zealand Merino wools are known as 1PP, which is the industry benchmark of excellence for Merino wool 16.9 microns and finer. This style represents the top level of fineness, character, color, and style as determined on the basis of a series of parameters in accordance with the original dictates of British wool as applied by the Australian Wool Exchange (AWEX) Council. Only a few dozen of the millions of bales auctioned every year can be classified and marked 1PP.[15]
In the United States, three classifications of wool are named in the Wool Products Labeling Act of 1939.[16] Wool is "the fiber from the fleece of the sheep or lamb or hair of the Angora or Cashmere goat (and may include the so-called specialty fibers from the hair of the camel, alpaca, llama, and vicuna) which has never been reclaimed from any woven or felted wool product".[16] "Virgin wool" and "new wool" are also used to refer to such never used wool. There are two categories of recycled wool (also called reclaimed or shoddy wool). "Reprocessed wool" identifies "wool which has been woven or felted into a wool product and subsequently reduced to a fibrous state without having been used by the ultimate consumer".[16] "Reused wool" refers to such wool that has been used by the ultimate consumer.[16]
