Editing Wool (section)

==Characteristics==
[[File:Hogget fleece.JPG|thumb|Champion [[Glossary of sheep husbandry|hogget]] fleece, [[Walcha, New South Wales|Walcha]] Show]]Wool is produced by [[Hair follicle|follicles]] which are small cells located in the skin. These follicles are located in the upper layer of the skin called the [[epidermis]] and push down into the second skin layer called the [[dermis]] as the wool fibers grow. Follicles can be classed as either primary or secondary follicles. Primary follicles produce three types of fiber: [[Kemp (wool)|kemp]], medullated fibers, and true wool fibers. Secondary follicles only produce true wool fibers. Medullated fibers share nearly identical characteristics to hair and are long but lack crimp and elasticity. Kemp fibers are very coarse and shed out.<ref>{{Cite book|title=Storey's Guide to Raising Sheep|last=Simmons|first=Paula|publisher=Storey Publishing|year=2009|location=North Adams, MA|pages=315–316}}</ref> [[File: Wool fleece and top.jpg|thumb|Fleece of fine New Zealand [[Merino]] wool and combed wool top on a wool table]]
Wool's crimp refers to the strong natural wave present in each wool fiber as it is presented on the animal. Wool's crimp, and to a lesser degree scales, make it easier to [[spinning (textiles)|spin]] the fleece by helping the individual fibers attach, so they stay together. Because of the crimp, wool fabrics have greater bulk than other textiles, and they hold air, which causes the fabric to retain heat. Wool has a high [[specific thermal resistance]], so it impedes heat transfer in general. This effect has benefited desert peoples, as [[Bedouin]]s and [[Tuareg people|Tuareg]]s use wool clothes for insulation.

The felting of wool occurs upon hammering or other mechanical agitation as the microscopic barbs on the surface of wool fibers hook together. Felting generally comes under two main areas, dry felting and wet felting. Wet felting occurs when water and a lubricant (especially an alkali such as soap) are applied to the wool which is then agitated until the fibers mix and bond together. Temperature shock while damp or wet accentuates the felting process. Some natural felting can occur on the animal's back.

Wool has several qualities that distinguish it from hair or fur: it is [[crimp (wool)|crimped]] and [[Elasticity (physics)|elastic]].<ref>{{cite book|last=D'Arcy|first=John B.|title=Sheep and Wool Technology|publisher=NSW University Press|location=Kensington|year=1986|isbn=0-86840-106-4}}</ref> <!--Not true (steel wool, rock wool, etc. in US While in the United States the term 'wool' is usually restricted to describing the fibrous [[protein]] derived from the specialized skin cells called [[Hair follicle|follicles]] in sheep, in the UK the term may be used of any long curling fiber such as 'wood wool', 'wire wool', etc.<ref>Australian Wool Corporation, Australian Wool Classing, Raw Wool Services, 1990</ref> -->

The amount of crimp corresponds to the fineness of the wool fibers. A fine wool like [[Merino]] may have up to 40 crimps per centimetre (100 crimps per inch), while coarser wool like [[karakul (sheep)|karakul]] may have less than one (one or two crimps per inch). In contrast, hair has little if any [[Cuticle (hair)|scale]] and no crimp, and little ability to bind into [[yarn]]. On sheep, the hair part of the fleece is called [[kemp (wool)|kemp]]. The relative amounts of kemp to wool vary from breed to breed and make some fleeces more desirable for [[spinning (textiles)|spinning]], [[felting]], or [[carding]] into [[batting (material)|batt]]s for quilts or other insulating products, including the famous [[Tweed (cloth)|tweed]] cloth of [[Scotland]].

Wool fibers [[hydrophilic|readily absorb moisture]], but are not hollow. Wool can absorb almost one-third of its own weight in water.<ref>[http://www.aussiesheepandwool.com.au/webcontent5.htm Wool Facts] {{webarchive|url=https://web.archive.org/web/20140526094929/http://www.aussiesheepandwool.com.au/webcontent5.htm |date=2014-05-26 }}. Aussiesheepandwool.com.au. Retrieved on 2012-08-05.</ref>
Wool absorbs sound like many other fabrics. It is generally a creamy white color, although some breeds of sheep produce natural colors, such as black, brown, silver, and random mixes.

Wool ignites at a higher temperature than cotton and some [[Synthetic fiber|synthetic fibers]]. It has a lower rate of [[flame spread]], a lower rate of heat release, a lower [[heat of combustion]], and does not melt or drip;<ref>[http://www.tricountyfarm.org/oregon_wool.asp Wool History] {{webarchive|url=https://web.archive.org/web/20080509143234/http://www.tricountyfarm.org/oregon_wool.asp |date=2008-05-09 }}. Tricountyfarm.org. Retrieved on 2012-08-05.</ref> it forms a char that is insulating and self-extinguishing, and it contributes less to toxic gases and smoke than other flooring products when used in carpets.<ref name="The Land p.46">The Land, Merinos – Going for Green and Gold, p.46, US use flame resistance, 21 August 2008</ref> Wool carpets are specified for high safety environments, such as trains and aircraft. Wool is usually specified for [[garments]] for firefighters, soldiers, and others in occupations where they are exposed to the likelihood of fire.<ref name="The Land p.46" />

Wool causes an [[allergic contact dermatitis|allergic reaction]] in some people.<ref>{{Cite journal|title = Allergic contact dermatitis in children: review of the past decade|journal = Current Allergy and Asthma Reports|date = 2014-04-01|pmid = 24504525|pages = 421|volume = 14|issue = 4|doi = 10.1007/s11882-014-0421-0|first1 = Shehla|last1 = Admani|first2 = Sharon E.|last2 = Jacob|s2cid = 33537360}}</ref>