This recipe makes a lotion which feels light, spreads easily and is not greasy at all. The smell is actually pleasant, and it works really well against insects AND the sun. I can't give a precise SPF value -- that depends not only on how thickly it is spread on, but also the strength of the various ingredients which contribute to the SPF varies from batch to batch. Anyway the SPF value does not have much concrete meaning.... What I can say is that a few weekends ago I took my family to watch Prince Harry play polo on Governor's Island for an hour under a punishing sun, and none of us got burnt or bitten. Other spectators were not so lucky....
Thanks to Scoochmaroo for inspiring me to publish this. Her sunscreen is quite different from this one (very thick and stiff -- but also a whole lot less complicated) so I though it worthwhile to offer this alternative.
Step 1: On sunscreens
UVA rays are much longer waves, and therefore they penetrate deeper into the skin. These are the rays responsible for the telltale signs of aging, and also for the #1 killer skin cancer, melanoma.
Some ingredients, such as zinc and titanium oxide provide "broad spectrum" protection, which means they block both UVB and UVA rays. These chemicals protect the skin by deflecting and diffusing the waves, but their drawback is that they make skin white when they are first applied. To counter this manufacturers have developed nano zinc and titanium particles which don't make you turn white. Unfortunately, since they are so tiny, they can penetrate into the bloodstream, where the damage they could wreck has not been studied. Unless you want to be part of a long term, unpaid, unmonitored, high risk medical study, avoid nano particles. Don't be so lazy and vain. Take a minute to rub in the regular zinc oxide, after a while you won't look like a zombie. I avoid titanium dioxide because it is carcinogenic (for sure on mice, possibly for us too) -- so why take the unnecessary risk when zinc does the job just as well?