Knowing that regular zinc oxide was used as a sunscreen many decades ago just isn’t convincing enough to many people that it is an effective sunscreen. You want research, data, proof. I get it. Plain zinc oxide is not currently marketed as a sunscreen so there are no current data or research to my knowledge. Hopefully, that will change. But through some digging, I have found technical proof that conventional zinc oxide is an effective UVA/UVB protector in skin care. In the book, Sunscreens: Development, Evaluation, and Regulatory Aspects, an authority in the cosmetic science industry, one article mentioned an old 1947 publication that disclosed the absorption spectrum for several metal oxides. This valuable article “Zinc Oxide in Face Powders” cited the percentage of light transmitted by ZnO, TiO2, china clay, chalk and talc at various wavelengths. The following values were obtained from powders compressed into 920 nm thick films as considered applicable to face powder use:
UVB wavelengths range from 290 – 320 nm and UVA rays range from 320 – 400 nm. The percentage of light transmissions was much higher, over 50%, for the other metal oxides. These values indicate that ZnO is a better UV protector than TiO2. These data were not for nanoparticles. It pertained to regular zinc oxide for cosmetic use – a 920 nm layer (less than one micron) is not very thick. You do not need to look like a clown to be protected with regular zinc oxide. Aside from diaper rash and other anti-inflammatory ointments, zinc oxide today is commonly found in blush, powders, and eyeshadows. It is one of the three main ingredients in mineral makeup, the latest hype in the beauty market.
I am very close to finishing my sunscreen e-report. I apologize for the delay. Summer, holidays, family, you get the idea. But mainly, I don’t want to put out a half-hearted attempt.