When it comes to animal fibers, Merino wool is the most common. For centuries, merino is valued for its warmth, strength, and “breathability.” Chances are, if you visit your local yarn shop, you’ll likely find that merino fiber is used in nearly one-third of all yarn sold.
Merino is the oldest and most established sheep breed in the world. This breed of sheep was likely introduced into Spain from North Africa in the 12th century. During the 15th century, Spain monopolized the Merino wool industry, which was a substantial source of income. In fact, the trade was so lucrative that the export of Merinos from Spain was punishable by death. It was not until the fall of the Spanish empire in the late 1700s did the prized breed begin to make its way to other parts of the world.
Merino fiber has a high and fine crimp which gives it an excellent insulation quality with a ton of bounce. There are several grades of merino wool which is based on the thickness of the fiber (measured in microns). For perspective, on average, a human hair is 40-50 microns.
- Ultrafine Merino: <17.5 microns
- Superfine Merino: 17.7 – 18.5 microns
- Fine/Extra Fine Merino: 18.5 – 19.5 microns
- Fine – Medium Merino: 19.6 – 20.5 microns
- Medium Merino: 20.6 – 22.5 microns
- Strong Merino: 22.6 – 24 microns
Despite its relatively short staple length of 2.5 – 4 inches, merino has a high tensile strength. Spinning and plying the short fibers more tightly helps increase durability; you’ll find that the best yarns made from merino have a very tight twist.