Although not sold for that purpose, detergent formulations with optical whiteners provide some protection from light in the UVA range of 320 to 400 nm, explains Mr. Kaufmann. Optical whiteners led to the development of the Tinosorb products, which provide protection in the UVA and UVB 290 to 320 nm ranges. The UPF scale was developed in Australia and is a mechanical measure of the amount of ultraviolet light that penetrates a fabric. SPF, on the other hand, is an in vivo measure that compares treated skin to an unprotected control. The amount of UPF that clothing provides depends upon several factors, including a fabric's density and color, and type of textile.
Dense fabrics offer a higher UPF than an open weave.
Deeper colored clothing scores better than light colored, and polyester and wool record high UPFs, as opposed to cotton, nylon and silk, which may score much lower. Tinosorb works particularly well on cottons, Mr. Kaufmann notes. A typical bleached white cotton shirt may have a UPF as low as 4 or 5 and may offer bare skin less protection than a sunscreen. Ciba says that using a laundry detergent with its product could significantly boost such a garment's ability to protect the wearer. Tinosorb accumulates with subsequent washings and does not easily rinse out with water or perspiration.