The Truth About UV Clothing
How does one test the latest UV blocking fabrics emerging on the market?Curiously, a number of light and laser testing facilities do not currently use the latest pending standard involving the averaging of invitro (lab) and invivo (human) field-testing and instead, choose to measure using the single standard Menzies/Az 1994 protocol, which is much more economical but far less accurate for the lightweight but complex yarn fabrications such as those employed in some highly regarded apparel products). Based on the laboratory credentials, some manufacturers have chosen to use an independent photonics lab that is well respected internationally in their field and is known to be very comprehensive in their test results. The facility created disciplined parameters for UV testing based more on the future interests of the industry. However, this method is also a much more expensive testing process.
The method employed by textile manufacturers seeking UV ratings for “woven yarns” is perhaps the one that is more incorrectly but commonly used today – and the test protocol is measured for stretch type fabrics used mainly for swim and active-wear. As leno fabric is a woven, with various degrees of porosity, such tests can still produce erratic results, especially with ventilated weaves and if the dyeing process involves optical brighteners and/or titanium dioxides in the pigments. These variables can wreak havoc on accurate results.
What can create controversy with the new fabrics?
As with any consumer goods purchase involving new and evolving technologies, one must be careful in relying on poorly researched magazine or newspaper articles, which can be quite misleading. Be sure to read the product detail descriptions on clothing tags or, if purchasing on-line, the description of a product on the web site. If a product does not say, for example, that it offers up to a 97% block, one should not assume that it does, even if other items within that product line so say so on the tag or in the on-line product description.
Do colors affect the UV protection level?
Yes, color is also an important point when considering clothing for the purpose of sun-block: Darker colors (especially indigo, navy and black) perform better because they can absorb more UV; however the trade-off is that they can create heat as a by-product. Lighter colors will reflect more, especially fabrics with optical brighteners. All everyday existing fabrics can be considered to have a sun-protective value, but unlike the creams that can have lower values, the current UPF rating system begins at the minimum UPF level of 15 to permit an independent classification.
When the ASTM D13.65 committee was created for the addendum to sun-protective fabrics in 1996, a number of textile manufacturers and light and laser specialists invested about 5 years in planning the testing protocol. Even today, it is still a work in progress and will be updated annually because the results are still inconclusive and merit more study. Naturally, some of the unique textiles being created today are, under current lab conditions, misunderstood.
What exactly is done in-lab to obtain a UPF rating? Is it different from “SPF”?
Yes, UPF involves a different criterion. While still a work in progress, the UPF [ultraviolet protection factor] is based on an entirely different curriculum of testing methods than the “SPF” measurements used for creams. For reasons of economy, the new rating system will use an invitro (lab) technique only, and includes wash, stretch and abrasion testing controls - as textiles are generally static in nature and do not change over time.
However while consistent in protocol, standard control testing methods may not yield similar results from lab to lab. While it is currently the most cost effective method to determine UPF, the test method will not recognize a textile with an averaged number less than UPF 15: for example, even if the fabric might test average a “19”, this number is always rounded down by 5 digits, in this case - rendering a “14” . Because of the minimum UPF level of 15, mentioned above, this result will render say a “19" to become a "0". Therefore, this example would view the swatch or article as under the minimum value for a UPF rating, and not yield a rating at all even though averaging a 19 in the initial tests. The same could be said for a tested level of “20”, which by the prescribed margin of error would result in a UPF of 15. The maximum rating designate for a textile is UPF50+; however, 30 is more than adequate for the majority of individuals with sun-sensitive conditions.
What are the differences in fabric types available?
Today, people interested in sun-care products have different demands. Like the protective blocks and lotions, there are many types of textiles used in apparel that are available to meet various degrees of desired performance based on lifestyle. Tighter (opaque) weaves and darker colours are usually designed to be worn close to the skin, and can assist in blocking a higher proportion of ultraviolet light for longer periods. Whether stretch or woven, these fabrics are used in clothing that is opaque and is worn alone as a fashion lifestyle or as swimwear. A drawback to the tighter weaves and stretch fabrics is reduced ventilation and increased heat retention - which can be a serious liability to certain individuals in hot climates.
Other fabrics employ a complex lightweight weave and design structure that is somewhat looser to encourage cooling airflow, and will provide additional coverage. These garments are designed to be worn over other favourite summer-weight weather apparel. This type of clothing is a sun-care “booster” but might not be an appropriate recommendation for persons requiring a high degree of opaque protection or have prescriptive conditions that renders one particularly light sensitive – a drawback to the looser weaves and (lighter colours) will be the allowance of more UV transmission than the opaque fabrics for areas of bare skin under a single layer of fabric, especially if the area is pulled tightly over the skin and exposed to prolonged time in the sun. This drawback is remedied in the careful construct and loose design of such apparel, as the UV light transmittance decreases exponentially and dramatically, every millimetre away from the skin.
Some manufacturers’ hats and accessories, through their fabrication, have a much higher level of protection, and certain styles with multiple layering and fusing agents will afford a UPF rating up to 40+. While the clothing is a protective & effective adjunct as long as it is worn as designed, with the appropriate size chosen by the individual for the particular activity and worn loosely over other summer-weight apparel.