More Fascinating Wool Facts

We marvel at the complexity of our world and wool is no exception. What a Creator we have!

wool folicle

The outside of wool is a protective layer of scales called Cuticle Cells. They overlap each other like tiles on a roof. The exposed edges of the cells face away from the root end so there's more friction when you rub the fibre in one direction than the other. This helps wool expel dirt and gives it the ability to felt. These are also the scales that are either burned or filled with a polymer for Superwash wool. Wool felts when fibers are aligned in opposite directions and they become entangled. The scales have a waxy coating which stop water from penetrating the fiber, but allows for absorption of water vapor. This makes wool water-repellant and resistant to water-based stains.

The interior of the wool fiber is called the Cortex and make up about 90% of the fiber. It is made up of long tapering cells that overlap and are surrounded by the cell membrane complex. This membrane, which runs throughout the whole fiber,is made up of proteins and waxy lipids. The molecules in this part of the fiber have fairly weak intramolecular bonds, so with prolonged wear and abrasion, they tend to break down. The weak bonds also make this area susceptible to strong alkaline conditions, which is why washing with a pH-neutral detergent is generally recommended.

There are 2 main types of cells in the cortex

Each one has a slightly different chemical composition. In finer fibers, these cells are arranged in 2 distinct halves. In coarser fibers, the arrangement is less distinct. These are the cells that create the crimp in wool. The 2 types of cell expand differently when they absorb moisture,which causes the fibers to bend. When the cells are arranged in 2 distinct halves, there is more crimp,as in the Merino Wool. The more random these 2 types of cells are arranged, the coarser the fiber because it creates less crimp. Crimp relates directly to fiber diameter. The crimp in wool fibers makes it soft and springy to touch. Crimp will also add bulk and trap a large volume of air between the fibers, which give wool good insulation properties. Finer wools with more crimp create fabrics that drape better than coarser wool fibers with less crimp.

Cortical Cells have a complex interior structure. They are:

  • Macrofibril
    • Inside the cortical cells are long filaments called macrofibrils. These are made up of bundles of even finer filaments called microfibrils, which are surrounded by a matrix region.

  • Microfibril
    • These cells are even smaller units, lying inside the Matrix. The microfibrils are like re-bar that is embedded in concrete to give the concrete strength and flexibility. The microfibrils contain pairs of twisted molecular chains.

  • Matrix
    • The matrix consists of high sulfur proteins. This makes wool absorbent because sulfur atoms attract water molecules. Wool can absorb up to 30% of its weight in water and can also absorb and retain large amounts of dye. The Matrix region is also responsible for wool's fire resistance and antistatic properties.

  • Twisted Molecular Chain and Helical Coil
    • These cells are protein chains that are coiled in a helical shape like a spring. The chains are stiffened by hydrogen and disulphide bonds, linking each coil of the helix, helping to prevent it stretching. Though the helical coil is the smallest part of the fibre this little spring gives wool its flexibility, elasticity and resilience; helping wool fabric keep its shape and remain wrinkle free.