Why Is the Wool So Warm?

All wool is warm because, unlike silk, cotton, or polyester, there are tiny scales on the hollow, air-filled fibers that cause them to interlock and trap insulating air. Also, wool has a natural crimp, or wave, that remains even after processing and washing. This means that less wool touches the skin than is the case with other fibers. In addition, wool continues to absorb moisture​—up to 30 percent of its weight—​without feeling damp to the touch.

Significantly, silky vicuña wool is finer than any other wool. And, usually, the finer the wool, the finer the quality. Fine wool means finer yarn and finer cloth​—cloth that feels soft, light, and warm. A scarf made of vicuña is so fine that it can be drawn through a wedding ring. Because the fine fibers are very sensitive to chemical treatment, vicuña wool is normally used in its natural golden color.

The vicuña fleece has been appreciated since the time of the Incas, before the Spanish conquest of the 16th century. Millions of vicuñas thrived in the Andes in those days. Every few years the Incas would organize thousands of people to surround entire mountains and trap the herds of vicuñas so that they could be sheared. Vicuña cloth was a respected mark of rank; only the highest-ranking ones in the kingdom could use it. Today, it is almost impossible to obtain legally.

Touch its coat if you can. It is the finest wool on earth, with hairs less than half the diameter of the finest sheep’s wool.

The vicuña needs that insulating coat, since it lives at an elevation of from 12,000 to 18,000 feet [3,700 to 5,500 m] on the slopes of the Andes Mountains. There, near the snow line, days are delightfully sunny, but at nightfall the temperature suddenly drops to many degrees below freezing.