Photonics Samples UV-Safe Clothing

Brent D. Johnson

Skin cancer has been on the rise in the US, Australia and Europe for the past decade. More than 51,000 new cases are reported to the American Cancer Society each year. Dermatologists have recommended a battery of preventive measures, and photonics is doing its part by helping researchers determine the protective effect of fabrics.

Since the early 1980s, Patricia Cox Crews of the University of Nebraska-Lincoln has used a Cary UV/VIS spectrophotometer to evaluate dyes and UV absorbers. Since the mid-1990s, she has employed a Cary UV/VIS spectrophotometer from Varian Australia Pty. Ltd. to measure the UV transmission of clothing. She said that the most influential variable is the porosity of the fabric, but the type of material and its condition also play a part. Cellulose tends to be more UV-transparent, so clothing manufacturers may apply UV-absorbent finishes or chemicals similar to those used in sunscreens to block out harmful rays. Bleached fabrics are less protective than darker ones, and dry fabric is more protective than wet.

Crews recently acquired a Cary 50 spectrophotometer with a fabric-protection accessory and an accompanying fabric software package. She said that the primary advantage of the system is the magnetic specimen holder with crosswise and lengthwise error-markings that presents the sample to the instrument port, making the system simpler and faster to use.

Scattering effects from translucent or opaque materials can compromise the measurement of UV protection factor, so the new system transmits the light from the xenon flashlamp through the fabric, and then through a UG11 filter and into an integrating sphere, which removes directional preferences. This configuration also eliminates any fluorescence that might result from whitening agents in the fabric.

Traditionally, the market for UV-protective clothing has targeted chemotherapy patients who may be sensitive to sun exposure, but it is expanding to include sports enthusiasts, such as hikers, climbers, bicyclists and boaters.