I was asked in my lovely wool/silk group on Facebook (feel free to join!) to say something about the excellent UV protection properties of wool/silk . All the "conventional" wool/silk shops and many blogs claim that wool/silk provides outstanding UV protection . But how much truth is there to this claim?
Since I had to deal a lot with the topic of sun protection due to my own physical characteristics (pale skin, reddish tint in my hair, freckles on every visible part of my body) and a small, also sun-sensitive, dwarf son, I am happy to give a summary of my research.
This research turned out to be much more extensive than I initially anticipated, and especially more scientific than some of you might be interested in. Therefore, I'll first provide a brief summary for those simply interested in my conclusion, followed by a summary of the scientific articles on the topic. I'm not a medical professional, certainly not a dermatologist – the results presented here are purely my own interpretation of the current state of research and not medical advice!
Generally speaking, the topic of sun protection with textiles is not simple, and a lot of misconceptions are still spread through blogs and forums. For example, I read in one blog that cotton provides the best UV protection, even though every scientific study I've read advises against cotton as a UV protectant. Others talked about how artificially added UV protection on T-shirts practically washes out – I can't confirm this based on my research, but I can confirm that UV-protective clothing, after certain stresses (stretching or getting wet), can only offer a tiny fraction of its original UV protection and then becomes useless.
Summary recommendations
If you want to be absolutely sure, then my recommendation is exactly that of the Hohenstein Research Institute - you should use clothing that has been tested according to the UV Standard 801.
UV Standard 801, which is based on the most unfavorable wearing/usage conditions (worst case scenario) 1
Here, the clothing is tested even when wet, stretched, and after several washes.
Otherwise, the unanimous opinion of all scientific texts is that while one cannot necessarily tell how good a garment's protection is just by looking at it, polyester and wool generally provide the best possible UV protection , whereas cotton, linen, and similar materials fail in the vast majority of cases.
Research findings of the last 20 years
Interestingly, the idea of using textiles for sun protection is still quite new in the Western world. Traditionally, the focus here has been on sunscreen and/or avoiding the sun. It was only in the last 10 years that the realization spread from Australia that appropriate clothing could also provide effective protection against harmful UV rays.
Well-known examples of effective sun protection using textiles have long been practiced by the Tuareg in Africa with their indigo-dyed fabric panels, or the famous saris from India, where several layers of silk are wrapped over each other as sun protection.
Two different concepts of sun protection come into play here.
The blue dye used by the Tuareg improves the otherwise rather poor UV protection of cotton fabric. Generally, dark and vibrant colors are better than light clothing, as the dye also absorbs UV rays. This is even more pronounced with the Tuareg's indigo blue than with other shades.
In contrast, with Indian saris, it is primarily the type of fiber that determines the UV protection. Fabrics such as linen or cotton are rather poorly suited for UV absorption; the best options are specially treated synthetic fabrics, wool, or silk, as the Hohenstein Institute has determined: ¹
The protection against UV rays offered by natural fibers such as cotton or linen is relatively low. A white T-shirt provides a UV protection factor of only 10-15. This is because cotton fibers themselves reflect or absorb very little UV radiation. This is especially true when they have absorbed moisture – the fibers then become virtually transparent. [...]
Natural silk has a relatively high UV protection factor because, like modern synthetic fibers, it contains mattifying fiber components that reflect and absorb UV rays. Furthermore, uniform fiber structures with small gaps in the woven or knitted fabric prevent UV radiation from reaching the skin. Depending on the color, the UPF ranges from 20 to 30.
The following basic rules, which determine the UV protection of a textile, can be found at Hautsache.de:²
- The type of fiber: Wool, for example, is good because the fiber has one of the highest radiation absorption rates and therefore also low UV permeability.
- Fabric weight: The heavier the fabric, the higher the protection.
- The yarns: Dense fabrics are best.
- The color: The darker and more intense the colors, the better the protection.
- Surface texture: Textured is better than smooth.
- Fit: Loose-fitting clothing offers better UV protection than tight-fitting clothing.
Stiftung Warentest criticizes not only the variety of labels used in testing procedures in its tests, but also the UV protection of shirts declared as UV shirts in general - even cotton clothing costing €70, which was specifically advertised as having UV protection, failed miserably in some tests.
While children's hats receive "good" and "very good" ratings for the UV protection of the fabric, the results for outdoor clothing and children's T-shirts are often below average.
Moisture causes cotton to swell and acts like a magnifying glass on the skin. However, it can also increase UV protection, although the fabric may appear darker when wet. Washing can also decrease UV protection because the fabric thins, or increase it because the fibers shrink .
But how can you determine which clothes are suitable for the beach and summer?
All scientific articles agree that while it is difficult to determine a garment's UV resistance simply by looking at it, there are clear trends.
BMCDermatol writes:
Although it was not possible to study the parameters independently we have demonstrated the following trends. Polyester and wool fabrics usually provide sufficient UV protection (UPF 30+), while other fabrics, such as cotton, linen, and viscose, frequently offer poor UV protection. 7
(Translation: Although it is not possible to test all parameters independently, the following trends have emerged: Polyester and wool usually have sufficient UV resistance, whereas other fabrics such as cotton, linen or viscose often provide poor UV protection)
The Bochum Skin Tumor Center³ points out that the choice of clothing also plays a significant role in UV protection. It should be fairly obvious that short tops or bikinis do not protect against sun rays, but stretching clothing also reduces UV protection considerably. It is therefore recommended to wear dark, loose, and airy clothing.
Gamblicher et al (2001) also found in their research "Protection against ultraviolet radiation" that merino wool in particular provides excellent UV protection.
Haerri et al (2000), Reinert et al (1997) and Hilfiker et al (1996) also showed
Natural merino wool absorbs radiation throughout the entire UV spectrum even when completely untreated.
As an English wool and silk shop correctly wrote:
This is like slathering your skin in chemical sun tan lotion - but without the chemicals.
("Wearing wool and silk is like drowning your skin in chemical sunscreen - but without the chemicals")
However, as Hautsache.de correctly points out, there is a problem with wool:
Viscose, cotton and linen fabrics offer less protection against UV radiation.
such as those made of wool, silk, and nylon. [...] But especially in summer, we prefer to wear light, lightweight clothing instead of the dark green wool sweater.
Wool/silk as summer clothing
Well, with wool/silk (www.danischpur.de) we have a wonderful alternative – the fabric is light and cool in summer thanks to the silk content, making it a real alternative to a cotton shirt. (And it's also more comfortable to wear, as you don't have that wet feeling against your skin when you sweat).
During our trip through New Zealand, Australia, Thailand and South Africa, the little one wore wool/silk almost exclusively - mainly because he loves the clothes himself and we were glad not to have to wash them constantly, but also because they are so comfortable to wear in summer and offer good sun protection.
With additional measures such as avoiding the midday sun, wearing a hat and (especially) applying cream to our feet, we actually managed to keep Mr. Cheese White completely sunburn-free throughout our sabbatical.
Sources:
- https://www.hohenstein.de/media/pdf/328-DE_18_HOH_UVSchutz_Hintergrundinfos_2011_8459.pdf
- https://www.hautsache.de/Die_Haut/Licht-und-Haut/Hautschonende-Bekleidung-mit-Sonnenschutz.php
- http://www.hauttumorzentrum-bochum.de/sonnenschutz-durch-bekleidungstextilien.html
- http://www.uvstandard801.com/de/uv_standard_801/uv_standard_1/uv_standard_2/uv_standard_2.html
- Stiftung Warentest https://www.test.de/Kleidung-mit-UV-Schutz-Hemd-und-Hut-steht-ihm-gut-1688475-2688475/
- http://www.campaignforwool.co.nz/wp-content/uploads/2011/12/MERINO-FOR-MILITARY-APPLICATIONS.pdf
- https://bmcdermatol.biomedcentral.com/articles/10.1186/1471-5945-1-6
- Hilffiker, R. Kaufmann, W. Reinert et al 1996 Textile Research Journal 66
- Gamblicher T. et al 2001 Protection against ultraviolet radiation by commercial summer clothing, need for standardized testing and labeling, BCM Dermatology
- European Standard, 2002, EN 13758-1, Textiles, Solar UV protective properties, Method for testing of apparel fabrics