I just bought a sunscreen whose only active was Zinc Oxide in the form of Zinclear-IM. I checked on the web, and apparently Zinclear-IM is manufactured by a company called Antaria. Using something called Indexing Matching Technology (hence the IM, whatever the hell index matching technology means is beyond me) they've been able to make a virtually transparent form of micronized zinc oxide with a mean particle size of over 1 micron (which =1000nm). That's pretty exiciting, seeing as most micronized/nano zinc oxide forms are micronized down to 100nm and below, which jeopardises their UVA protecting ability. So Zinclear seems ideal: at 1000nm you'd probably get amazing protection, and certainly looking at the transmittance graphs, Zinclear provides 0% transimittance to about 370nm, at 400Nm there's only like 20% transmittance.
Anyone want to comment?