How Laundering Affects UV Blockage in T-Shirts

Overview

Purpose: Ultraviolet (UV) radiation from the sun can damage human skin, and many rely on clothing for protection. However, the UV blocking ability of fabric may decrease after repeated laundering. In this project, I tested whether laundering reduces UV blockage of common fabrics and whether different fabric types are affected differently. I hypothesized that cotton would lose a significant amount of its UV protection after 50 laundering cycles compared to other fabric types. Procedure: To test this hypothesis, I used 40 T-shirts representing four fabric types: 100% cotton; 60% cotton/40% polyester; 90% polyester/10% spandex; and 92% rayon/8% spandex. For each fabric type, five shirts were laundered 50 times in a standard washer and dryer, while five shirts were left before laundering as controls. A clay holder kept the UV lamp and meter in the same position for every measurement. Each shirt was placed over the UV meter at a fixed distance from the lamp, and transmitted UVA and UVB radiation was recorded. Results: After 50 laundering cycles, UV-blocking ability decreased, and the amount of change depended on the fabric type. 100% cotton showed large increases in UVA and UVB transmission after laundering. Polyester-rich fabrics showed little change. Rayon/spandex fabrics showed the largest increases in UVA and UVB transmission. Conclusion: Laundering clothing increases UV transmission, allowing more UV light to pass through fabric. The results show that fabric type plays a larger role than laundering alone in determining clothing protection against UV radiation.

Competition history

• CSEF 2026 Materials Science (Junior Division) · Entry J-13-12

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