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How to Increase the Ultraviolet Protection Factor (UPF) rating of a T-shirt Part 1
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Whatever style you wear this summer, you want it to be comfortable. And what is more cool and enduring than a cotton T-shirt 
you can accessorize to your heart’s content. You may already have several T-shirts you cherish.
But have you thought about the shirt’s UPF? That stands for Ultraviolet Protection Factor, the standard rating system that tests and measures a fabric’s ability to protect the skin from the initial onset of skin reddening caused by UV-B rays.
UPF values
15 to 24 good sunburn protection
25 to 39 very good sunburn protection
40 to 50 excellent sunburn protection
25 to 39 very good sunburn protection
40 to 50 excellent sunburn protection
A new white cotton t-shirt has a UPF of about 5. So that means about 1/5 of UV rays are transmitted through to your skin. Wash the t-shirt once and it shrinks, decreasing the spaces between the fibers in the fabric. This tightening of the weave increases UV protection by increasing the cover factor, the surface area of the fabric covered by fibers.
“Cover factor is the most important factor in achieving UPF ratings of at least 15 UPF, the lowest value for classifying a fabric as Ultraviolet protective,” says Kathryn Hatch, Ph.D., professor, Agricultural and Biosystems Engineering, University of Arizona, Tucson, AZ.
That’s about 1/15 of UV Rays getting through to your skin. However, UV radiation can also penetrate some fabrics, allowing UV rays to be transmitted. In addition, “Skin that is not covered is NOT protected. Garments styled to cover the most skin are better for sun protection,” says Dr. Hatch.
You can also wash the t-shirt several times in most laundry detergent which will deposit optical whiteners on the cotton fibers. “The more washings a fabric undergoes, the higher the chemical build-up,” says Dr. Hatch.
To achieve broad spectrum UVA/UVB protection, you can add a UV absorbing compound to your laundry detergent during washing. Rit SunGuard, recommended by the Skin Cancer Foundation, can increase the UPF of a T-shirt from 5 to 30 after a single washing and will last for 20 washes.
“The big difference between SunGuard and optical whiteners is that SunGuard is much more effective in absorbing the most skin reddening UV rays,” says Dr. Hatch.
You can purchase one-ounce boxes of Rit SunGuard at Michael’s Arts and Crafts at 1600 Saratoga Ave, Ste 433, San Jose, (408 379-4717).
Interviews wih Kathryn Hatch, Ph.D.
Michael Martin, M.D.
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environmental health ·
sun protection ·
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- How to Increase the Ultraviolet Protection Factor (UPF) rating of a T-shirt Part 2
- How to Increase the Ultraviolet Protection Factor (UPF) rating of a T-shirt Part 1
