When you film it in UV, sunscreen appears completely black from the first drop out of the bottle, meaning it absorbed all UV. The 15 minutes might be for applyi

When you film it in UV, sunscreen appears completely black from the first drop out of the bottle, meaning it absorbed all UV. The 15 minutes might be for applying or getting absorbed before there's a chance to get wiped off. This is a good video to highlight this [0], the sunscreen part is in the second half. Probably many more like it. [0] https://www.youtube.com/watch?v=o9BqrSAHbTc https://www.youtube.com/watch?v=o9BqrSAHbTc