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Geez, where did I get my wires crossed? (Don't answer that!)

Well, I treated everyone to an erudite but totally irrelevant rumination on SiO2, anyway. :)

ZnO2 of course already is widely used in total sunblock products but as I said eariler, the lifeguard and surfer type dudes and dudettes look like they have toothpaste on their noses. Then came a clever idea with the introduction of "Zink" or something like that, which comes in different colors, so you can look like a Native American about to go to war.

A practically colloidal, well I guess it's larger than colloidal, but in any case small enough to be transparent and yet retain its UV blocking ability is astonishing; I'd labored under the misimpression for years that Zn02 ointment USP, as it originally was prosaically sold, blocked UV by simply being like paint and blocking everything.

200 nm.. hmm, that's 2000 Angstrom, right? The stuff has to block wavelengths above 2000 A (I don't know how to make the little circle above the A so forget it), to arounsd the upper end of 2000 and into 3000 I think, to block UVB; I forget the wavelengths for UVA, UVB, and "longwave" (non-burning / non-tanning UV used in "black lights" if anyone remembers those).

It'd be nice if the particle size had a bearing on what is filtered/bounced off, so that products could be "tuned", say, to totally block all UVA & UVB, i.e. a "sunblock", or to permit UVA and block UVB. Or ideally (but if particle size is directly related to what gets in, then a mixture of two different sizes would be needed), something that allowed 5% UVB and all UVA through.

(Real tanning type dudes know that a small amount of UVB seems to perk up melaninogenesis (if I spelled that right, I'll be amazed).)

I don't do the sun thing for my looks; improving that would need an act of God. But I do find tanning beds in the wintertime help perk me up; I probably have mild SAD; and also, maintaining a mild tan helps control my oily skin; it's a little embarassing being 44 and buying Stri-Dex.

So in the process, I've become rather an obsessive nut on the subject, like I have about lawn grubs and aquariums, What are Raccoons' Favorite Foods, etc.

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