Why does wool keep you warm even when wet?

The merino fiber has special material properties when wet. It has the ability to absorb up to a third of its weight as moisture. The moisture is bound in the form of water vapor in the fibers and also stored between them. If the merino fiber absorbs moisture, absorption heat is generated and the fibers heat up. The big advantage: as long as the merino fibers can absorb moisture, they actively transfer heat to the body. The protein molecules in the fibers release energy in the form of heat when they come into contact with water. Depending on the fiber quality, the temperature can rise by up to ten degrees.

As long as the merino wool is slightly damp and the fibers are not yet saturated with water molecules, heat is released. Unfortunately, when the clothes are completely soaked from the rain, the effect of the absorption heat is lost. Nevertheless, Merino keeps you warm because the movement of the fibers causes frictional heat. By the way: If it starts to rain lightly, it makes sense to wait a bit before putting on a rain jacket, as the resulting absorption heat makes the garment feel pleasantly warm. 

In order to make optimal use of the heat generated when wet, it is an advantage if the Merino clothing is completely dry beforehand. The fibers are then able to reach their full potential and absorb the greatest amount of moisture. When drying, the best result is obtained in a warm, low-humidity room. In front of an oven or on a heater works very well. The change of clothing made of merino should then be packed waterproof before an excursion so that it does not absorb moisture beforehand and only warm up when you put it on.