Not only limited to UV-inhibiting textile use, sun protective clothing may also adhere to specific design parameters - including styling appropriate to full coverage of the skin most susceptible to UV damage. Long sleeves, full collars, and full-length trousers and skirts are common styles for clothing as a sun protective measure.
A number of fabrics and textiles in common use today need no further UV-blocking enhancement based on their inherent fiber structure, density of weave, and dye components - especially darker colors and indigo dyes. Good examples of these fabrics contain full percentages and/or blends of heavy weight natural fibers like cotton, linen and hemp or light-weight synthetics such as polyester, nylon, lycra and polypropylene. Natural or synthetic indigo dyed denim, twill weaves and canvas are also good examples. However, a significant disadvantage is the heat retention caused by heavier weight and darker colored fabrics.
As sun protective clothing is usually meant to be worn during warm and humid temperatures, some UV-blocking textiles and clothing may be designed with ventilated weaves, moisture wicking and antibacterial properties to assist in cooling and breathability.
Sun protective clothing was originally popularized (but not exclusively used) in Australia as an option or adjunct to sunscreen lotions and sunblock creams. Sun protective clothing and UV protective fabrics in Australia now follow a lab-testing procedure regulated by a federal agency: ARPANSA This standard was established in 1996 after work by Australian swimwear companies. The British standard was established in 1998 after work by Rohan on UPF testing of fabrics used in outerwear. Rohan launched its first range of UPF tested clothing in its May 1995 Moving On catalogue www.rohan.co.uk. The tests used by Rohan, were validated by the NRPB (National Radiological Protection Board) and formed the basis of the Britsih Standards Institute standard. The US standard was established in 2001. (To date, the focus for sun protection is swimwear, appropriate hats, shade devices and sunglasses for children.) UPF testing is now very widely used on clothing used for outdoor activities.
The original UPF rating system was enhanced in the United States by the ASTM (American Standards and Testing Methods) Committee D13:65 at the behest of the FDA (Food and Drug Administration) to qualify and standardize the emerging sun protective clothing and textile industry. The UPF rating system may eventually be adopted by interested apparel and domestic textile/fabric manufacturers in the industry at large as a "value added" program strategic to complement consumer safety and consumer awareness.
Factors that affect the level of sun protection provided by a fabric, in approximate order of importance, include weave, color, weight, stretch, and wetness. In addition, UV absorbers may be added at various points in the manufacturing process to enhance UV protection levels.
There is some indication that washing fabrics in detergents containing fabric brighteners, which absorb UV radiation, might increase their protective capability. Studies at the University of Alberta also suggest that darker colored fabrics can offer more protection than lighter colored fabrics.
A relatively new rating designation for sun protective textiles and clothing is UPF (Ultraviolet Protection Factor). Unlike SPF (Sun Protection Factor) that measures only UVB, UPF measures both UVA and UVB.
Developed in 1998 by Committee RA106, the testing standard for sun protective fabrics in the United States is the American Association of Textile Chemists and Colorists (AATCC) Test Method 183 This method is based on the original guidelines established in Australia in 1994.
AATCC 183 method defines the UPF rating for a fabric/textile as the ratio of UV measured without the protection of the fabric (compared to) with protection of the fabric. For example, a fabric rated UPF 30 means that if 30 units of UV fall on the fabric only 1 unit will pass through. A UPF 30 fabric that blocks or absorbs 29 out of 30 units of UV is therefore blocking 96.7% UV. UPF tests are normally conducted in a laboratory with a spectrophotometer or a spectroradiometer.
AATCC 183 should be used in conjunction with other related standards including American Society for Testing and Materials (ASTM) D 6544 and ASTM D 6603 ASTM D 6544 specifies simulating the life cycle of a fabric so that a UPF test can be done at the end of a fabric’s life cycle – which is when most fabrics provide the most reduced level of UV protection. ASTM D 6603 is a consumer format recommended for visible hangtag and care labelling of sun protective clothing and textiles. A manufacturer may publish a test result to a maximum of UPF 50+.
While there is some correlation between the amount of visible light that passes through a fabric and the amount of UV that passes the same fabric, it is not a strong relationship. Based on some of the new-technology fibers and textiles designed for the sole purpose of UV blocking, it is not always possible to gain a good understanding of the UV protection level of a fabric simply by holding it up and examining how much visible light passes through the fabric.
Sun protective clothing and textile/fabric manufacturers are currently a self-regulating industry in North America, prescribed by the AATCC and ASTM methods of testing.