Everything you need to know about merino wool

Merino Wool - The Functional Fiber in Detail

Merino Wool - The Functional Fiber in Detail

At the end of the 1980s, many outdoor fans considered functional clothing made of synthetic fibers to be the ultimate - after "normal" wool and cotton had become obsolete due to "uselessness". At that time, only a few pioneering outdoor companies relied on merino wool. In the meantime, however, almost all outdoor clothing manufacturers have products made from this "new wool" in their range. The merino sheep has become, so to speak, the favorite animal of many sports and outdoor enthusiasts. Anyone who has ever worn a garment made of merino wool will never want to do without it again. But what is it about this high-tech fiber from nature? In the following, we will take a closer look at merino wool and its properties:


Everything you need to know about merino wool

Merino wool is a natural product obtained from the wool of sheep - namely from the wool of merino sheep. The animals originally come from the North African plateaus of the Atlas Mountains and are today one of the oldest and most resistant sheep breeds in the world. Merino sheep lived there under extreme, often adverse weather conditions, the kind you only find in the mountains when you spend all four seasons there at once. They had to - and still have to, for example, in the New Zealand Southern Alps - withstand extreme temperature fluctuations of minus 20 to plus 35 degrees. That is why they have a coat that is perfectly adapted to such harsh conditions. In the Middle Ages, the sheep finally reached Spain, where their wool was sold as valuable "Spanish wool". In the 18th century, the first Merino sheep were then exported to Australia, which has since become the world's largest exporter of this precious commodity, along with other wool-producing countries such as New Zealand, South Africa and South America.


Merino wool by nature has some very advantageous properties:

  • It doesn't scratch.
  • It warms when it's cold.
  • It cools when it is warm.
  • It warms when it is wet.
  • It does not develop unpleasant odors even after repeated wear.
  • It is water and dirt repellent.
  • It is particularly light with high thermal performance.
  • It has a natural UV protection.
  • It is not electrostatically charged.
  • It is flame retardant.
  • It does not wrinkle.

Of course, all these properties are optimal when it comes to making functional clothing for outdoor activities. But first, let's look at the most important properties in detail and find out why merino wool actually has them.


Merino sheep belong to the breed of fine wool sheep. The fur of these sheep consists of particularly fine, soft and strongly crimped hair with a fiber thickness of only 16.5 to 24 microns (the fiber thickness of wool fibers is specified in the unit micron; 1 micron corresponds to 1 micrometer, i.e. 1 thousandth of a millimeter). This means that the fibers of merino wool are only about half as thick as "normal" wool fibers and only a quarter as thick as a human hair. Now the finer wool fibers are, the more they curl when they touch the skin. While thicker wool fibers hardly curl at all, merino fibers curl with up to 40 changes in direction per centimeter. As a result, the nerve endings of the skin are significantly less irritated, and there is no unpleasant itching. The human sensitivity threshold above which fibers are perceived as scratchy is about 25 microns. That is why normal wool is perceived as scratchy, while merino wool feels pleasantly soft on the skin.


MERINO WOOL Ideal when freezing!

Merino wool has excellent insulating properties when it is cold. This is due to the ingenious structure of merino fibers. The fibers of merino wool consist - in relation to their total volume - up to 85% of air. The fine and wavy fibers lie so loosely on top of each other that air chambers can form between them. And since air is a poor conductor of heat, it provides excellent insulation - against both cold and heat.

The effect is comparable to a window that has a double pane of glass. The air between the two panes has an insulating effect - both in winter and in summer. So merino wool does not warm by itself, but it prevents our own body heat from escaping by trapping insulating air pockets. It keeps our body heat where we need it when the ambient temperature is cold. Additionally, merino fibers have fewer points of contact with the skin due to their high degree of crimp, which means they dissipate less heat. In summary: The advantage of the crimped fibers of merino wool is that more insulating air is trapped and less heat is dissipated.


Our human body has a natural air conditioning system. In warm ambient temperatures or during intense physical activity, we start to sweat. The body secretes moisture in the form of sweat to cool down and keep the body temperature at a constant level.

Merino wool provides excellent moisture transfer.

Merino wool can support this endogenous function of the body in an optimal way. It functions like a second skin, which further enhances the cooling effect. Because on the one hand, the air cushions of the merino fibers insulate not only against cold, but also against warm ambient air. And on the other hand, the fibers behave uniquely towards moisture. Their moisture management has never been matched by any artificially developed textile fiber. Merino wool fibers can absorb up to one-third of their own dry weight in moisture - the figure for man-made fibers is less than ten percent. The fibers owe their high moisture absorption capacity to their chemical structure. They are hygroscopic - that is, they can bind moisture in the form of water vapor, and do so in particularly large quantities and particularly quickly. Sweat or rain moisture is quickly transported into the fiber interior via a fiber network of tiny channels.

At the same time, the fiber surface remains dry because it repels water. That's why merino wool still feels dry even when it has absorbed a lot of moisture into its fiber interior. Ingenious, isn't it? The hygroscopic fibers function like a reservoir that serves to optimally compensate for moisture fluctuations in the environment.

Warm ambient air now ensures that the moisture absorbed into the fiber interior evaporates on the outside of the garment. However, for the process of evaporation - i.e. the transition from the liquid to the gaseous state - the water molecules require energy. And they extract this from the nearest "body" - i.e. the merino fibers - in the form of heat. The fibers cool down, and with them the skin and your own body. This process is called evaporative cooling, and it causes a pleasantly cooling sensation on the skin.

Synthetic fibers, on the other hand - as already indicated - can store almost no moisture in their fiber interior. This results in a particularly rapid removal of moisture to the outside. This causes a buildup of heat, and the body reacts by increasing sweat production in order to cool down. This naturally costs correspondingly more energy, which is then no longer available for performance - for example, during sporting activities. Studies conducted by the University of Graz have already demonstrated a higher increase in lactate in athletes who wore synthetic fiber textiles. So all in all, the natural function of merino wool also contributes to a higher performance of the body - what more could you want?


Compared to cotton or synthetic fibers, merino wool retains its good material properties even when wet. Unlike a cotton shirt, a merino shirt does not stick uncomfortably to the skin when it gets damp. And in a sweaty garment made of merino wool, you also don't experience an unpleasant chill, as you do when you're at the summit in a synthetic shirt. But what is the reason for this?

Ultimately, this warming effect in a damp state is also based on the ability of merino fibers to absorb moisture. When moisture is absorbed, a so-called exothermic process takes place, during which absorption heat is generated. This means that the fibers heat up when they absorb moisture. Sounds incredible? But it is true! Merino wool actively warms as long as it absorbs moisture. This is because the protein molecules of the merino fibers release energy in the form of heat when they come into contact with water molecules - so much so that the temperature increase can be as much as ten degrees, depending on the fiber quality.

This process continues until the wool fibers are saturated with water molecules. So a slightly damp merino baselayer can generate heat, but a one that is completely soaked from the rain can't, of course. But even then, the merino piece still keeps you warm - due to the frictional heat of the fibers that is generated mechanically during movement. But: In light, incipient rain, it actually makes sense to wait a short time before putting on a rain jacket. After all, a slight wetting of the merino shirt ensures that it starts producing pleasant warmth.

Of course, the warming process works best when the functional clothing made of merino wool is completely dry beforehand, because then the fibers can best exploit their potential of moisture absorption. Therefore, it makes sense to dry the garments completely before starting an outdoor venture - especially if the venture is to take place in winter. The best way to do this is, of course, in a warm room with the lowest possible humidity, such as a room heated by a stove or heating air. A change of clothes made of merino wool should be packed in a waterproof bag or plastic bag before the tour, so that the wool fibers do not absorb moisture from the ambient air during the tour. After all, they should only start to warm when you put on the garment!



The unpleasant odor that we often notice on ourselves and our clothes after sweating is not caused by the sweat itself. Freshly formed sweat is odorless. We only start to smell when skin bacteria begin to break down the sweat into its component parts. Sweat serves as a food source for them, and they particularly like to multiply in warm and moist regions - for example, in the armpits. Of course, sweat and skin bacteria also settle in our clothing, so that at some point - at least if it is made of synthetic fibers and has no odor-inhibiting treatment - it also begins to smell unpleasant. So why should this be any different with garments made of merino wool?

Synthetic fibers have a smooth surface to which sweat and bacteria can adhere particularly well. Merino fibers, on the other hand, have a scaly surface that you can imagine as a roof with tiles. On it, the bacteria have no chance. In addition, the fibers absorb the moisture of the sweat so quickly that the bacteria do not even get to break down the sweat. The water-repellent fiber surface also does not allow a humid climate to develop, which the bacteria would need for their growth.

Finally, wool fibers have a specific fiber protein (like all animal hair) - keratin - that simply breaks down the bacteria responsible for the foul odor. So merino wool has a natural antibacterial effect - and it's permanent, because the effect doesn't wear off. Even the silver ions incorporated into synthetic fibers, which are intended to inhibit odors, cannot match this ingenious biological function. But that's not all! To perfect this mode of action, merino fibers also have a mechanical self-cleaning effect. This is because the core of the fibers consists of two different types of cells that can absorb different amounts of moisture. When absorbing moisture, they therefore swell unequally. This creates a constant friction process through which the fiber cleans itself again and again.


Even though merino fibers can absorb relatively large amounts of moisture into their fiber interior, their fiber surface is water and dirt repellent. This is because the fiber has the wool fat lanolin there. Although a large part of it is washed out when the wool is processed, a residue remains on the fibers. The wool grease acts like a protective layer. Dirt and odors stick to the fiber surface and do not penetrate it. Lanolin can also have an analgesic effect on rheumatic joint complaints, which is why people with this problem also like to turn to wool clothing. Due to the strong crimping of the fibers, water drops also have only a very small attack surface and simply roll off due to their surface tension. This works in exactly the same way as with certain plants, whose fine hairs on the surface ensure that water drops roll off.


We probably don't need to think much more about the advantages of merino wool in the outdoor sector. From the above-mentioned reasons, it should be obvious that this "high-tech wool" is particularly suitable for outdoor use. In summary, merino fibers are true multi-talents that do what is needed in any situation - they warm in cold, they cool in warm, they warm when wet, they do not develop unpleasant odors, and last but not least, they feel pleasant on the skin. With this flexibility, merino wool garments are naturally perfect for outdoor pursuits. After all, whether it's warm, cold, wet or dry outside, those who are out and about in nature need clothing that is just as flexible as the weather we expose ourselves to.

Above all, the temperature- and climate-regulating properties of merino wool are a great advantage in many outdoor situations. Body temperature always remains at a comfortable level despite varying temperature conditions and different activity levels. And these conditions are often encountered - especially in alpine pursuits. Weather changes or temperature fluctuations play a big role when you cover a lot of altitude. If you are still sweating in the valley, you may start to shiver slightly on the airy ridge. And when you have to take a break at the summit, a material that can keep you warm even when damp is invaluable. Also for activities such as cycling, ski touring or skiing, where you find very different activity levels and temperature conditions uphill and downhill, the temperature-balancing wool is excellent.

The odor-inhibiting property of merino wool is particularly advantageous when you are out for longer periods of time and have no opportunity to wash. Especially on a trekking tour or backpacking trip, where you are traveling as light as possible, you want to have merino clothing with you that you can often wear indefinitely. After all, it takes time for these to smell so bad that you feel the need to wash them. Also, thanks to the elastic fibers, the fabric of a merino shirt won't wrinkle much even if you squeeze it into a backpack for days on end.

Basically, there are almost no limits to the use of merino wool garments in the outdoors. Whether you are trail running, climbing, yoga or even in everyday life - the material is just great everywhere. However, a few disadvantages should not remain unmentioned. The merino fibers are not quite as mechanically resilient, robust and tear-resistant as other natural or synthetic fibers.

Especially if you wear a shirt made of pure merino wool directly under a heavy backpack, damage to the fabric can occur. If weight and pack size of a garment are the most important criteria for selection, textiles made of synthetic fibers usually perform better. And drying times are also usually faster. Sometimes garments made of pure merino wool are perceived as too warm in summer, despite their cooling properties. And last but not least, there are particularly sensitive people who also find merino wool scratchy.

However, the textile industry in the outdoor sector has now found possible solutions to eliminate the aforementioned disadvantages of textiles made of merino wool - namely with the use of so-called blended fabrics.


When it comes to sustainability, it's also worth taking a closer look when buying a product. On the one hand, merino wool is by nature a particularly sustainable material. On the other hand, however, there are also certain problems in the area of animal husbandry, which are among the unattractive aspects of wool production. But first, let's look at the advantages of merino wool in terms of sustainability.

Merino Flock

Merino wool is a naturally renewable raw material. Merino sheep can be sheared up to twice a year and yield up to ten kilograms of wool per animal. In addition, the production and processing is particularly resource-saving and environmentally friendly compared to the production of synthetic fibers. Synthetic fibers are produced on the basis of petroleum, which requires a large number of chemicals and the use of large amounts of energy. In addition, synthetic fibers are almost rot-proof. Synthetic clothing takes 30 years or more to decompose.

It must therefore inevitably end up in landfills after its use. Products made of pure merino wool, on the other hand, are biodegradable without leaving any residue. They can be thrown on the compost heap without hesitation. A merino shirt buried in the ground can be completely composted within 90 days and can then be used as fertilizer in the garden. In addition, merino wool naturally possesses properties such as its UV protection or odor inhibition and thus does not require environmentally harmful chemical additives. After all, the "technology" is already contained in the fiber. Last but not least, the self-cleaning function of merino fibers also protects the environment, as you don't have to wash the garments as often.

However, animal welfare is not always the top priority in merino wool production. In Australia and New Zealand, there is the problem of fly maggot infestation in the keeping of merino sheep, which ends in the fatal disease myasis. In this case, the animals are virtually eaten from the inside. Especially in warm temperatures, as found in the Australian summer, the flies lay their eggs in the poorly ventilated skin folds at the anus, which are smeared with feces and urine. Especially in Australia - the country with the most merino wool producers - a brutal method is unfortunately used to prevent fly maggot infestation - the so-called mulesing.

This involves a surgical method of cutting off a plate-sized portion of the skin folds around the anus, tail and vulva of the lambs when they are up to eight weeks old. This is usually done with a hot cutting device, and without anesthesia and while fully conscious! The wounds are not treated further, but are left to heal and scar on their own.

The animals are thus subjected to great pain during this bloody and mutilating procedure. Studies show that the sheep still flee from their tormentors 113 days after such a procedure - so traumatizing is this experience. To date, there are few uncontroversial alternatives to solving the problem of fly maggot infestation. Especially since fly maggots, like Merino sheep, were probably first imported to Australia and New Zealand during colonial times. More elaborate and expensive methods include regular shearing of the skin folds around the anus, regular inspections of the sheep, and timely medical intervention in the event of an infestation. Animal welfare activists are therefore calling for the selective breeding of sheep with fewer skin folds on their buttocks. In fact, however, Australian Merino sheep have been deliberately bred to have more skin folds, thus yielding a higher yield of wool.

So when buying a merino product, in light of these cruel facts, one should consciously make sure that only mulesing-free merino wool has been used. This is guaranteed, Many manufacturers also state very precisely and traceably where they source their wool. Merino wool that does not come from Australia or New Zealand is always mulesing-free, as the problem of fly maggot infestation simply does not exist there.

Most manufacturers of outdoor products do not use wool that has been mulesed at all. However, if you are unsure, when in doubt, check with the manufacturer directly or with the relevant retailers. Also, a very low price of a merino garment is sometimes due to the use of the mulesing practice. In most cases, it is worthwhile to take a closer look anyway and rather spend a little more money. But for that you usually get impeccable quality delivered and supports not least the species-appropriate husbandry of merino sheep.


You can of course wash merino wool at 30 - 40 degrees without fabric softener with a wool detergent. Here, however, you must please make sure that the wool detergent does not contain enzymes. The enzyme protease is responsible for breaking down the keratin in the merino wool. This then ensures the hole-forming wool in the clothing. If you are unsure, it is better to use a pH-neutral mild or functional detergent, then you will enjoy your merino wool longer.

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