The chemical and physical composition of the Merino fibre provides it with an excellent natural elasticity that improves with moisture content.

Extensible when wet

The Merino fibre is highly extensible, a characteristic that increases as it absorbs water.
(Fig 1)

When wet, a Merino fibre can be extended up to 30% without damage and when the force is removed the fibre will recover its original dimensions completely. If a Merino fibre or garment is stretched while dry, steaming or wetting with water can be used to speed up the rate of recovery.  

Helix to sheet transition

Merino’s extensibility is due to the ability of the fibre to undergo a reversible change from a helix to a sheet formation as it is elongated. The helices progressively unfold when the fibre is stretched between 2 and 30%, and the process is known as alpha to beta transition.

Summary

The Merino fibre can transform from a helix to a sheet formation upon elongation, giving it high extensibility that increases with moisture content.

Source

• CSIRO, “Wrinkle recovery/resilency/recovery/wrinkle  recovery/natural elasticity/ appearance/shape retention/soft handle”, 2005.

All figures and tables courtesy of CSIRO unless otherwise noted.