How to beat the heat in Merino wool

The Fibre

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The natural properties of the Merino fibre are said to help insulate the body against temperature extremes on either end of the scale - so science set out to prove it.


All textile fibres - wool, cotton and synthetics - have the ability to absorb moisture from the air and release it again as humidity levels shift. It’s how well they do it that determines the effect these changes have on the skin’s temperature: the higher proportion of a textile’s body weight that it can absorb in water, the better.

Looking at fabrics side-by-side, it’s little surprise that man made synthetics fare poorly next to their natural counterparts. Polyester can only muster up the ability to absorb just one percent of its weight, while nylon - also called polyamide on many garments - does a touch better at seven percent. 

Moving to natural fibres, the saturation water content improves significantly. Cotton manages a more respectable figure of 24 per cent, but it is wool that takes the podium finish above all other textiles with the ability to absorb up to 35 per cent of it’s own weight in water.

The complex molecular structure of wool fibres delivers the unique moisture buffering characteristics permits the absorption of excess water as humidity increases, releasing it as humidity drops.



Scientific trials quantified these absorption figures in real world scenarios. Putting an adult through her paces in a four-stage exercise program in a variety of temperature and humidity levels, temperature and moisture content of the skin were monitored and measured.

Wearing a Merino wool T-shirt, the skin’s surface moisture content was maintained within the 30-50 per cent range even when exercising at temperatures of 39 degrees Celsius. This range is significant because prolonged exposure to humidity extremes outside this normative range or sudden shifts in humidity levels can adversely affect health, compromising the skin’s ability to protect against pathogens, UV and chemicals.

In contrast, performing the same activity in a cotton tee caused the garment to become soaked - the fabric struggled to buffer skin moisture and moderate surface temperature.

Further trials dressed subjects in half wool/half polyester vests and again measured moisture and temperature levels of the skin during exercise. The conclusion of scientists was that wool more effectively controlled the microclimate of the body. Polyester was unable to offer a similar shielding effect.

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