In summer, it’s hard to avoid the sun’s rays if you want to enjoy the longer days and warmer weather, so skin protection is a top priority for any outdoor activity. Getting that projection has never been easier with UPF-rated shirts, pants, and hats that let you know how much sun exposure you’re getting when you wear them. Here’s what you need to know about the science behind those numbers.
The term “UPF” means Ultraviolet Protection Factor, a rating designed to show you how much a protection a piece of clothing can give you from sun rays that can cause sunburn, premature aging, and skin cancer. It is similar to the SPF (Sun Protection Factor) for sunscreen, but applies to fabrics instead of creams and sprays.
“We are seeing more questions about UPF,” Diana Wyman of the American Association of Textile Chemists & Colorists (AATCC) told the Outdoor Guys from Jesse Brown’s. “There’s a lot of startup companies interested in this idea of sun protection, but it is a challenge. It is something that is regulated.” The AATCC creates testing standards for fabrics manufactured by companies around the globe, to allow for even comparisons between products.
Wyman says that a lot of clothing claims are subjective but UPF is not. A UPF tag on apparel means what it says. So how do you interpret UPF, exactly? Wyman explained that, too.
A fabric’s UPF is a measurement of how much sun can be screened by a piece of fabric. For instance, a UPF of 25 will allow 1/25 of the sun’s rays to pass through. A UPF of 50 allows 1/50 of the sun rays to reach the skin. The ASTM International (formerly known as the American Society for Testing and Materials) rates a UPF of 25 as “Very Good,” and a UPF of 50 as “Excellent.” A UPF below 15 is not rated since the ASTM does not consider a rating that low to provide UV protection, according to Wyman and the AATCC.
Factors like coverage, how much the fabric needs to stretch to cover skin, the fabric’s color, as well as fiber, construction, and fabric finish, chlorinated water exposure, and even laundering all affect UPF while the garment is being used, reminds Wyman. She adds, surprisingly, that shrinkage and detergent can actually improve UPF over time.
And while she’s at it, Wyman explains the difference between UV-A and UV-B rays. Yes, both are part of the sun’s spectrum, and both can harm the skin. We are most sensitive to shorter wavelengths of the sun’s rays, which are UV-B rays. But more of the UV-A rays, which are longer, reach the earth, so the “danger zone” of ultraviolet rays falls somewhere in the middle, according to Wyman. In short, UV-B rays will make the skin redder, but UV-A are far more abundant, making the “peak” danger for our skin is in the upper part of the UV-B range.
The AATCC testing standards measure how much of the UV-A and UV-B rays can pass through a fabric. The result is the UPF rating, like those you find on sportswear, T-shirts, pants, and hats at Jesse Browns. Stop by and take a look at Jesse Brown’s sun protection line of apparel, and you won’t have to worry about having fun in the sun!
Shop Columbia UPF Clothing and Gear at Jesse Brown’s