Australian Merino has a much greater capacity to absorb moisture vapour than most textiles, which is why it has such excellent breathability.

Water repellent but moisture absorbent

Merino’s surface is hydrophobic, which means it repels water. Consequently, after a brief shower, water will tend to bud on the surface of a Merino garment, and can be brushed off. However, the Merino fibre has a very significant capacity to absorb moisture vapour.

The highest regain

The weight of water able to be absorbed by a fibre as a percentage of its dry weight is known as its regain. For synthetics the regain can be as low as 1%, while for cotton it’s 24%. Merino has the highest regain of the popular textiles with an ability to absorb 35% of its own dry weight in water (Fig 1).

Internal binding sites

Merino has the great capacity to absorb moisture vapour than synthetic fibres because its internal structure is more complex than synthetic fibres, creating more sites where moisture can bind.

Better breathability

This higher regain means that Merino is better able to absorb the moisture vapour produced by a garment wearer and so lower the humidity in the micro-climate between the skin and the garment (Fig 2). This explains why Merino is renowned for its breathability – its capacity to reduce the feeling of clamminess for the wearer.

Summary

Merino is naturally water repellent but has the capacity to absorb more moisture vapour than many other apparel fibres – up to 35% of its own weight – which is why Merino garments have such excellent breathability.

Sources:

• CSIRO, “Wool for Comfort: Benefits of moisture absorbency in wool knitwear”
• CSIRO, “Moisture buffering”
• CSIRO, “Wool for active sports: Comfort and Performance Advantages”
  

All figures and tables courtesy of CSIRO unless otherwise stated