by Kyle Barraclough
Not for most people. Thanks to advancements in textile technology and animal science, Merino clothing with next-to-skin comfort is rapidly gaining popularity. However, comfort largely depends on the raw wool used and, to a lesser extent, manufacturing methods. In other words, even superfine Merino clothing can be itchy if not made properly.
Advancements in wool production notwithstanding, it must be noted that a small percentage of people cannot wear wool due to skin sensitivity which is also discussed herein.
The number one feature of Merino wool clothing that determines where it rates on the continuum from comfortable to uncomfortable is the diameter of the wool fiber measured in microns: one millionth of a meter (1 / 1,000,000 m).
When coarse fibers with large diameters are spun into yarn and then woven or knitted into fabric, these large diameter fibers protrude from the fabric and abrade the skin. Everyone’s nerve endings are different, so people respond to stimulation in different ways. But because their diameter is greater, the wool fibers don’t bend. Instead they press against the skin and irritate nerve endings which produce the prickly, itchy feeling.
In the past, wool items contained a high percentage of coarse fibers (>24 microns). Most people would feel this as itchy and the itchiness became associated with the wool itself, not the original micron used. The bottom line is that the coarser the fiber, the itchier and pricklier the fabric.
Comfort Begins With Raw Wool Selection
Thick and itchy old wool lost market share to smooth fibers like polyester which was invented in 1941. With a soft, non-prickly and non-itchy hand feel it became very popular. Consumers were able to find lighter, softer and more comfortable items made from these materials that also exhibited many of the same properties as wool.
In response to the competition, the wool industry turned to technology and animal science to meet consumer demand.
Wool fabric contains a spectrum of microns. When a Merino wool shirt specifications are that the yarns in the fabric are 18.5 micron, for example, there are finer and coarser fibers that compose that yarn. It is impossible to make wool clothing of one single micron. This happens because sheep don’t just grow one micron measurement. There is a spectrum of microns even on any single sheep. So, sheep are sheared and the wool is collected and is all bunched together. The raw wool then needs to be separated according to size.
The ability to identify and reduce efficiently these few fibers in massive lots was basically impossible without technological advancements. It would have been very similar to finding a needle in a haystack. That’s why old wool shirts, blankets, etc. were itchy. For perspective, it only takes 5% of wool fibers above 30 micron to make an itchy fabric. That is such a small amount that eliminating enough coarse fiber from wool batches was basically impossible under old production methods.
As mentioned, all wool products contain fibers across a spectrum of diameters. The wider the spectrum, the more coarse fibers are present. To compete with the softer and smoother fabrics of cotton and polyester, wool growers needed greater ability to control that spectrum. So, they developed technology to increase the ability to produce finer fabrics.
One such advancement was the Laserscan. True to its name, it was a laser scanning device used to measure fiber diameter faster and more accurately. This gave wool growers efficient control over the mean diameter of fibers; the variation of diameters within a sample; and the diameter distribution. This led to tighter spectrum batches with fewer coarse micron fibers for clothing yarns.
Merino wool producers are also taking the science of wool production to the next level. In addition to standard through ultrafine grades, some high-end garments can be made using a top capped fiber blend. As previously mentioned, all wool has variations in diameter across any given lot. Top capped means that the measurement will show an average diameter size below the cap. Essentially, a finer average.
Additionally, certain Merino types are very tight in spectrum, meaning no fibers exceed the cap. This gives the grower the ability to produce 100% pure fine or extra fine Merino wool that is not itchy. With the capability to grow and measure wool that does not exceed specific diametric tolerances, the resulting garment will exhibit superior hand feel and softness.
Merino sheep produce the finest wool compared to other varieties. The staple fiber from Merino sheep is much longer than other wool fibers. Additionally, Merino has a much smaller diameter than “old” wool (Standard Merino fiber diameter is approximately 23 microns with descending grades through Ultrafine coming in at less than 15 microns).
The combination of longer staple length and smaller diameter meant that Merino wool was inherently softer than regular wool because there were fewer fiber ends that could protrude through the yarn of the finished garment and press against the skin. For the fiber ends that did protrude, the smaller diameter meant that those fiber ends would bend when subjected to direct pressure and would not produce the prickly, itchy feeling of traditional wool with thicker, more rigid fiber ends. The result is a wool that doesn’t itch.
Everyone that tries a Merino shirt will tell you it doesn’t feel like cotton. It feels rough on the softer areas of the body such as the torso, back and shoulders. But, rough isn’t the same as itchy and the sensation often disappears once the wearer realizes it was never intended to be as soft as silk and becomes accustomed to the feel.
Wool Sensitivity and Wool Allergy
Some studies have shown that neither of these are factors! Hmmm, seems awfully biased. A customer with skin irritation would be right to question who funded those studies. However, no one argues that some people feel prickliness. The only question is the source. Wool allergies are extremely rare, but they do exist. And the studies only indicate that there isn’t a correlation between the prickliness and the allergy. The itchiness is caused by the other factors.
One such factor is the variability of skin thickness among humans. Pain receptors are located beneath the skin. So, it doesn’t take a PhD to figure out that people with thicker skin don’t experience the same irritation.
Skin Temperature and Humidity
Heat makes the skin softer and more sensitive to damage and irritation of all types. While colder temperatures have a tightening, or firming, effect on the skin’s surface. Merino’s moisture management and thermoregulation ability (discussed in other posts) keeps the body within a healthy temperature range. However, with Merino garments getting lighter weight with each innovation in production, many customers wear the clothing year round, including in hotter weather. This ambient heat can soften the wearer’s skin to the point where there is itchiness that wasn’t present in cooler environments.
Some customers have noticed that their 100% Merino t-shirts & polos are softer and more comfortable than their button-ups. The former are made from knitted fabric and the latter are woven. Studies have shown customers feel the difference.
However, a knitted shirt of 17.5 micron fabric can feel more prickly than a woven shirt at 18.5 microns. It all depends on how the yarn is constructed and the differing sensations of the skin from one individual to the next.
The first step is to know the micron of the garment being considered for purchase. Softness can improve and any remaining level of itchiness will recede, or be less noticeable, as the fiber diameter decreases from fabric to fabric. After making the right purchase decision, more hands on methods can sometimes improve softness. (But, this will depend on the fabric that is different from brand to brand.)
Another buying decision that affects comfort is the fit of the garment. Wearing looser garments, or layering, will increase comfort. Leaving some room between the skin and the garment will not only be less itchy, but it will also allow wool to perform thermoregulation and moisture wicking more efficiently. Tight wool across the skin will reduce the performance. A good example of controlling comfort is the popular 100% Merino base layer from some manufacturers. This is usually worn directly next to the skin with a tight fit. The wool presses directly, and sometimes strongly, into the skin. That just won’t be comfortable for some people and could be easily prevented with the right fit and the purchase of a finer micron fabric.
A more hands on approach to softening garments begins with washing. Machine washable wool is a modern innovation which tends to soften the fabric over time. In addition to basic care steps, this will also help to decrease, or eliminate, any remaining itch or prickly feel. (NOTE: Read manufacturer care instructions first. Not all wool is machine washable).
There are also home remedies that can be used to soften the wool. However, these should be performed with care as Merino wool is a natural fiber and the fabric can be stretched beyond the means to return when not handled carefully. These techniques include:
Understanding Your Wool Clothing
Knowledge is power, and the more one knows and understands about the characteristics of incredibly soft and versatile wool the better prepared they will be to maximize its utility and comfort. Merino is often more desirable than regular wool because of its superior hand feel and softness. It creates comfortable fabrics that take color exceedingly well and provide heat and moisture management for any activity level.
If some brands itch and others don’t, look at the manufacturer and the process. Knowing these details is the same as knowing the thread count of sheets. In the case of Merino wool, the lower the grade of fiber in microns, the softer and less itchy it will be.
Variations in itchiness may also be the result of a low average diameter but a wide spectrum. For example, a wide spectrum that averages 16 microns may seem to be superfine, but if the spectrum of the sample is wider, there will have been as many fibers above average as below.
In this case, check the care instruction, contact the maker or research to see what methodology is used in arriving at the diameter average. This problem can also be addressed by purchasing top capped fibers where the samples have a low spectrum of fibers and none are above the high end. Remember, it only takes 5% of higher diameter fiber to induce itchiness and disrupt comfort.
With this information, an informed buyer can find the right Merino wool fabric and can wear it in comfort, softness and without itchiness for years to come.
Making Non-Itch, Machine Washable Wool Fabric
Wool fibers have an outer layer of overlapping scales. Images of these microscopic scales are all over the internet and have been blamed mistakenly for the itchiness of wool. The bottom line is that the scales are much too small to be felt by the sensitive pain receptors on the skin. The actual reasons have already been stated. But, the scales are mentioned here to A) debunk the erroneous association with itchiness B) discuss why much of the ‘new wool’ on the market is machine washable.
Jagged Little Scales
The scales on wool fibers make it unstable because they can interlock when wet. This means that untreated wool items can shrink, or distort, from regular machine washing.
To address this issue, the wool industry has developed methods to reduce, or eliminate, the effect of the scales. The most common is the “Hercosett method.” The Hercosett process reduces the directional friction effect of the scales by leaving behind a thin polymer coating on the fibers. The resulting garment is machine washable since the fiber’s dimensional characteristics are stabilized.
However, there are drawbacks. The process uses chlorine to affect the scales on the surface structure of the fiber which means that chlorine gas is released into the air. Additionally, the reaction of chlorine with natural amino acids within the wool fiber means that absorbable organic halogens are present in the waste liquid. This renders a process that is unsustainable and one that impacts both air and water quality.
In addition to the environmental impact, the Hercosett treatment alters some of the desirable characteristics for wool. For example, the process causes fiber yellowing and is stiffer resulting in poor hand feel. Additionally, since the fibers are coated in a thin silicone polymer, other natural characteristics can be compromised by the barrier.
However, given the push for sustainable treatment methods for manufacturing there are new processes under consideration. These new treatments include: