What is Merino Wool and Why is it so Special?

What is Merino Wool and Why is it so Special?

Cover Image Source: ZQ Merino

To start with, we need to understand the commonly used term merino wool’. Merino refers to a breed of sheep that are medium sized animals, with a beautiful appearance, that are predominately bred for their wool. While they are becoming more and more recognised for their meat, the vast majority are bred primarily for their wool, and secondly for their meat as their carcass size is usually much smaller than that of meat sheep breeds. Merino sheep can have the iconic distinguishing spiral horns for their rams (males), while ewes (females) do not. They are exceptionally strong and hardy animals. Well adapted to almost all climates and excellent foragers. Making them ideal animals to be left to graze vast areas of high country, and largely fend for themselves.

Photo Credit Pippa Wigley Art of Merino Sheep in a High Country Station in New Zealand

Photo Credit: Pippa Wigley Art - New Zealand


Merino sheep need to be shorn at least once a year because their wool does not stop growing. Sheering involves cutting the woollen fleece from the body of a sheep – in the same way humans have a haircut or head shaved. If a merino sheep does not have their wool coat shorn and it is allowed to grow, it can cause heat stress, mobility issues and blindness.

 Woolmark image of Shearer Shearing a Sheep to remove its Fleece

Image Credit: Woolmark.com

Merino sheep are highly regarded for having a set of specific wool characteristics such as - a very greasy and dense fleece, a tight crimp structure in the fibre, and low micron measurements. This translates into a type of wool that has the ability to be spun into a finer yarn, and therefore a softer, lighter weight fabric. The wool has enhanced elasticity (stretch) and when spun into a yarn creates air pockets which contribute to the exceptional thermal properties we see of merino wool. The higher grease content of the wool helps to protect the wool by keeping it clean from dirt as it sticks to the outer greasy tips and does not penetrate the inner wool fleece. Giving that beautiful, near white wool colour. In addition Merino wool has the lowest micron measurements of any sheep – meaning it is the finest wool fibre. This translates into a softer handle and ability to be worn against the skin without irritation.

In terms of wearability and comfort for next to skin clothing – merino wool is the ‘king of the sheep breeds’.

Crimp Structure:

This measurement was traditionally referred to as ‘crimps per inch’. Merino sheep have the highest crimps per inch out of any other known breeds of sheep. It is the most vital part of sheep selection for breeding and was the most common method of estimating fibre diameter. Fibre crimp is a measurement used by wool classes when grading fleeces of wool. A fleece is graded, with the high end fleeces exhibiting the best characteristics and therefore the highest price.

Crimp Structure of Merino Sheep

Photo Credit: Bundaleer  

What does crimp mean when spun into a yarn?

Just to ensure we all understand the terminology, fibres come from the raw wool (known as a fleece) which is shorn (a type of haircut for sheep) from the body of a sheep. This fleece, like our hair, regenerates and grows back. Once a sheep is shorn, it’s fleece is graded by a specialist classer, cleaned, scoured and then sorted before being sent away to be spun into a yarn. A yarn in the term for a long continuous thread like structure which is made up of many wool fibres, spun together tightly. These yarns are then woven or knitted together to form a fabric, or a fully fashioned garment.

The crimp characteristics that merino wool fibres exhibit, high crimps per inch, enable the yarn to have greater elasticity, create air pockets and a finer spun yarn. All these factors translate to a final yarn, that is fine, soft, shows excellent elasticity and exceptional thermal properties.

Microns explained:

More recently, we have been able to accurately measure the diameter of a wool fibre, this measurement results in grading the fleece in terms of microns. A micron is a unit of measurement that measures the diameter of a wool fibre; one micron is equal to 0.001 mm. 

The lower the micron number, the finer the micron and in turn the softer wool handle (feel). Low micron wool is a stand out feature of merino wool, it is highly sought after, hard to achieve and therefore an expensive commodity.

Image of Micron Measurements from Woolmark

Image Credit: Woolmark.com 

So now let us look at the different micron grades of wool:

Super-fine wool: below 17.5 microns

Very fine wool fibres, top end, short supply. Used in luxury suiting.

Fine wool: 17.5-25 microns

Still very soft, yet slightly stronger and more durable. 17.5-18.5 microns is generally used in close to skin clothing. Between 18.5-25 microns slightly less soft and generally used in adults wear and classic fashion.

Mid-Micron wool: 25-35 microns

This type of wool is generally used for upholstery, or outer layer garments such as jackets and coats. Not close to skin.

Strong wool: 35+ Microns

A robust wool which is soft yet durable and is generally made into luxurious, hardwearing carpets. Many other uses can be found for such wool.

Merino wool is generally classed between 11.5 – 25 microns, therefore it is a superfine grade of wool. Super-fine micron wool is generally reserved for the highest of quality, luxury products such as Italian, designer suiting. There is a trade-off however, the finer the wool micron, the less durable. Therefore for garments that need to not only be next to the skin and soft, but also need be functional such as children's wear a 17-18.5 micron measurement is most appropriate. Still super-fine in handle and able to sit closely to the skin without irritation, but durable enough to withstand movement and tension from being worn on a body. Merino wool with a micron measurement between 19-25 microns is still soft to touch, and generally used in adult clothing.

Wilderling ZQ Certified Merino Wool Fabric used to Create Children's Wear and Baby Clothing

Image of Wilderling Merino Fabric knitted into a beautiful 18.5 micron, jersey knit fabric. We use this fabric to make our range of merino accessories and garments. 

High grease and fleece density:

As mentioned earlier the high grease content in merino wool helps to protect the inner fleece from dirt. It does this by the grease being on the outer tips of the wool (outside) where dirt will stick and therefore not penetrate the inner fleece. This leaves a very clean, almost white wool on the inside, a very unique and sought after property. However, there is a trade-off. A high grease content also contributes to a higher weight loss after the wool has been cleaned. This means that the yield is lower. Translating to less wool per sheep when compared to other breeds. Thus a contributing factor to higher price.

In Conclusion:

Every breed of animal has unique characteristics and reason why they are farmed. In terms of Merino sheep, they are bred for their highly prized and quality wool. Their wool is exceptionally soft due to the low micron measurement and able to be spun into an extremely fine yarn due to the wools high crimp structure. In addition Merino sheep breeds have a high grease content which protects the inner fibre, keeping it largely free and uncontaminated from dirt. All of these characteristics result in a wool that is able to be woven or knitted into a fabric that exhibits a silk-like feel, able to be worn next to the skin without irritation, has exceptional thermal properties (keeps you very warm), is light-weight (not bulky) and breathable (regulates your body temperature). Nature has created a truly remarkable fibre in merino wool, the perfect fibre to be made into a piece of clothing that can be used year-round for comfort and performance.

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