What are the properties of wool?

Microscopic Properties:
• Longitudinal Section (L.S.): The L.S. of wool has overlapping scales pointing towards the tip. The epithelial cells present on the surface are these scales. The number of scales on the surface of wool varies from 700 per inch in coarse wool to 300 per inch in fine wool.
• Cross Section (C.S.): The wool fiber is oval or epithelial in shape. The structure is similar to a sheath-core arrangement in which the cortex forms the bulk and accounts for 90% of the area. It is made of ortho and para cuticle cells and it is the difference in their behaviour that imparts crimp to wool. A fine wool has about 30 crimps in an inch while 1-5 crimp per inch is found in inferior quality wool.
The layer all around the cortex is called cuticle.

Physical Properties:
• Length: The length of wool fiber varies from 1.5 to 15 inches. On the basis of length, wool is categorised as short (1.5-5 inches), medium (2.5-6 inches), and long wool (5-15 inches). The variation in the length could be because of two reasons: breed and time duration between two shearings.
• Diameter: Very fine wool (merino) has a diameter of 18 micrometres and very coarse wool has a diameter of 40 microns. The average diameter ranges from 24-30 micrometre.
• Colour: The colour of wool depends on the breed of sheep. The scoured wool is mostly yellowish-white in colour and unscoured (presence of impurities such as fats and oil) has a colour ranging from white, grey, tan, brown to black.
• Lustre: The lustre of wool is low since the incident light that falls on the surface scatters on reflection due to the presence of scales on the surface of the wool.
• Crimp: Wool has a 3D crimp or waviness which aids in yarn manufacture.
• Tenacity: Wool is one of the weakest natural fiber and its strength decreases wet state since water breaks the hydrogen bonds in wool.
• Elongation and resiliency: Wool recovers quickly from wrinkling stating the excellent elasticity and resiliency of wool fiber.
• Heat and Electrical conductivity: Wool has a low heat and electrical conductivity. Also, the wool fabrics are known to provide warmth indicating the insulation property.
• Moisture regain: Wool has a good capacity to absorb water of about 13.6-16%. The fibers hold the water in wool and are not deposited on the surface.

Chemical Properties:
• Acids: Wool can withstand the action of acids (except very strong concentrated mineral acids).
• Alkalis: The wool protein (keratin) is sensitive to alkalis. And washing of wool is done using mild detergents and detergents with high alkaline contents are a big no.
• Organic Solvents: These solvents are employed for cleaning and stain removal do not damage wool.