| abstract |
A method of preparing sunscreens in which a dispersion of zinc oxide particles in an oil is formed by milling in the presence of a particulate grinding medium and mixed with cosmetically acceptable materials is claimed. The particles of zinc oxide have an average size of from 0.005 to 0.15 micron and the dispersion is substantially transparent to visible light but with an extinction coefficient at 308 nm (E(308)) and at 360 nm (E(360)) of at least 9 liters per gram per centimeter. The ratio E(360):E(308) is in the range 0.75:1 to 1.5:1. In a preferred method a mixed dispersion containing titanium dioxide and zinc oxide, having E(308) at least 15 liters per gram per centimeter, E(360) at least 10 liters per gram per centimeter and the ratio E(360):E(308) in the range 0.3:1 to 1.5:1 is used. The mixed dispersion is also claimed. The sunscreens prepared have a good balance of absorption for UVA and UVB radiation and better SPF values than those prepared from titanium dioxide and/or zinc oxide powders. |