press information

01-Aug-2011 | 324-EN

UV protective clothing tested

Great variations in quality in sailors' tee shirts

BÖNNIGHEIM (ri) As a result of being reflected off the water, the intensity of the sun's rays by and on the sea is particularly high. Having been commissioned by the 'Segeln' sailing magazine from the Jahr Top Special publishing house, the Hohenstein Institutes in Bönnigheim investigated the UV protection factor for four tee shirts and looked into the question of how well these protected active water sports people from high-energy UV radiation.

The UPF Ultra Violet Protection Factor was calculated for two tee shirts of the brands BOGIE (white) and A.W. DUNMORE (black), along with two tops made of chemical fibre mixtures from Hyphen (blue) and MUSTO (white).

In order to obtain the most realistic results possible, the Hohenstein Institutes experts calculated the UPF on the basis of the internationally-recognised UV Standard 801. Unlike other testing methods, this takes account of conditions of use which in the practical situation can have a negative effect on the UV protection provided. Accordingly, the UPF was calculated for the items of clothing not only in their new condition, but also after washing and subjection to mechanical stressing, in both wet and stretched condition. Quite frequently, this treatment results in a drastic reduction in the UV protective factor in comparison with the initial value for the new item in dry, unstretched condition. In the interests of presenting the worst-case scenario, under UV Standard 801 only the lowest value calculated for the product is shown in each case.

Under these conditions closely reflecting the practical situation, the Hyphen brand blue tee shirt (80% polyamide, 20% elastane) provided the best protection. With a UPF of 80, it provides even sensitive skin with adequate protection from the sun for the entire day.

With a UPF of 30, calculated in accordance with UV Standard 801, the white tee shirt in 100% polyester from MUSTO provides average protection. Its wearers can safely extend the time they spend in the sun by a factor of 30. The starting point is taken as the skin's inherent protection time depending on skin type (refer to table). For those with extremely light skin types, this is not adequate for a carefree day spent on the sea – such a person would also have to use a cosmetic sunscreen or keep to the shade.

The black cotton shirt from A.W. DUNMORE offers a UPF of only 15, meaning that additional measures are essential to protect even dark skin types from the sun.

The lowest degree of protection among the test items is provided by the white top in 100% cotton from BOGIE. With a UPF of 2, calculated after artificial ageing in both wet and stretched condition, it offers only minimal protection against UV radiation and is therefore of only limited suitability as a sailing outfit, even for darker skin types and shorter trips, without additional protection from the sun. Relatively speaking, the combination of artificial ageing, stretching and wetting has a significant effect on this shirt – in its new condition without any additional stressing, its UPF was still measured at over 14. In comparison with the other products, this garment compelling evidence of how crucial the type and construction of the textiles used is for the retention of sound UV protection under practical conditions.

Accordingly, Sabrina Köhler of the Hohenstein Institutes issues the following advice to be taken into consideration when purchasing UV protective textiles: "Unfortunately, it is not possible to assess the UV protective factor for any textile material on its appearance. Many manufacturers therefore quote a UPF for their products, but unfortunately there is no uniform regulation for calculating this and accordingly the statements made may not be directly comparable one with the other. If the UV protection is calculated only in new condition this is not sufficient, especially for clothing." The expert also advises prospective buyers to ask for products for which the UPF has been calculated in accordance with UV Standard 801: "As a result of everyday use, there are changes in material and colour which are significant factors for the provision of good sun protection. Under UV Standard 801, these factors are taken into account and only the lowest UV protection factor calculated is shown. If manufacturers shy away from these strict testing criteria, caution is recommended."

For example, with the MUSTO tee shirt there were discrepancies observed in the UPF arising out of the various methods of measurement: the top was designated with a UPF of 40+, calculated in accordance with European Standard EN-13758-1. This value was confirmed by the measurements undertaken by the Hohenstein Institutes for the new and unstretched material as well, and even exceeded. After artificial ageing and in wet condition, however, the UPF had fallen to 30, i.e. around 25% below the value stated for the product.

At the conclusion of its report, Segeln Magazine comes the corresponding conclusion: "Measurement in accordance with UV Standard 801 should be standard practice for sailing clothing."

The full test report on UV protective clothing is presented in Segeln Magazine, Issue 8/2011.

A few general recommendations on textile sun protection for active open-air sports persons from Sabrina Köhler of the Hohenstein Institutes in Bönnigheim:
• Chemical fibres such as polyamide and polyester provide "inbuilt" sun protection due to the added materials mixed in, for example titanium dioxide, as is commonly found in cosmetic sunscreens.
• Natural fibres such as cotton or linen and the yarns and woven fabrics produced from them do not have this "inbuilt" UV protection and also, as a rule, fail to exclude UV radiation to the same degree due to their uneven structure.
• With natural fibres in particular, the UPF (Ultra Violet Protection Factor) is reduced by moisture, as when they come into contact with water they change significantly in terms of colour and structure.
• Given the same basic material, dark-coloured textiles provide better protection against UV radiation than those in bright colours.
• Under stretching, woven materials display less change in UPF than knitted materials, as frequently used for tee shirts.
• High-grade UV protective textiles are made of chemical fibres of particularly tight construction and partially consisting of three-dimensional structures. However at the same time they are particularly breathable and quick drying when required.

The UPF (Ultraviolet Protection Factor)

As expressed, the UPF of textiles corresponds to the light-protection factor for cosmetic sunscreens. Always stated is the maximum time of exposure to the bright midday sun, depending on skin type and the resulting inherent protection present in the skin. A person of Skin Type I with blue eyes and a very light complexion has natural skin protection of approximately 5-10 minutes, according to this. If this person remains out in the direct sun without protection longer than this, he is risking sunburn. With the protection of a textile material with a UPF of 80, the time spent out in the sun can be extended without risk by a factor of 80, i.e. to a maximum of 6 to 13 hours (80 x 5 min. = 400 min. to 80 x 10 min. = 800 min.).
Good protection is provided by the white MUSTO tee shirt with its UPF of 30, with it therefore offering 30 times longer in the sun than without protection. However, when it comes to remaining outside in the sunshine for the entire day, especially for people with a light and very light skin type, this is still inadequate without any additional protective measures.
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