Anyhoo...the cleanser, surprisingly, did not leave behind a greasy film that you might expect. The directions have you massage it into your face for one to two minutes, I guess to make sure the product really adheres to your skin. But it washes off just like any other cleanser. It's hard to believe that anything is truly left behind. I wrote to the company asking how this product worked, and, alas, I was told that "this technology is considered proprietary information". However, even though St. Ives didn't want to divulge their top-secret technology, apparently, someone else found out, because after only one search for "cleanser with SPF," I found out the following info from DailyBeauty:
This SPF 10 source works because it’s encapsulated in a positively-charged silica shell that sticks to the negatively-charged skin, so when the cleanser is rinsed off, the sun protection stays. In addition to protecting against 90% of UVB rays, Protective Cleanser also contains antioxidant vitamin E.
Now I wish I could say I was really dedicated to finding out if this cleanser truly protected, but I have to say I was not at all willing to go outside and offer up my already sun-damaged face to the harmful rays of the sun for research, knowing that I would never go out with a sunscreen that only contained SPF10. Like I said, I'll use this cleanser, but will keep in mind that the SPF10 I'm getting from it is just a little extra insurance, not my only source of protection.