Did you know that sunscreen is actually tested on humans? The sunscreen is applied to a group of people’s skin then the group is put in a room and exposed to high intensity UV light designed to mock peak sun conditions. The participants are then monitored until their skin begins to turn red. SPF is determined based on the number of minutes until this occurs. For example SPF 15 means it took approximately 15 minutes before skin redness occurred. SPF 30 means it was approximately 30 minutes and so on. A lot of times we think of SPF as being a measure of how effectively the cream blocks UV Rays, but keep in mind how this number is determined when you think of what it means. There are studies that show that anything higher than SPF 50 is actually only incrementally more effective at blocking UV rays. That’s because at SPF 50 the cream is already blocking 98% of sun rays. SPF 100 blocks 99%. To determine is a sunscreen can be classified as water resistant, the cream is applied to a group of people. They then sit in a hot tub then get out and wait till the skin dries before conducting the above test to see if it still provides the SPF listed on the label. The subjects may also get in and out of the water help simulate real life conditions.
Now that you understand how SPF is determined in a lab, I’ll tell you how we determined if our sunscreen recipe actually works. We started with research, learning what ingredients would actually provide some level of sun protection and to what extent. We chose to use the ingredients with the highest individual SPF ratings and balanced our recipe for consistency, protection from harmful sun rays and ease of use. Our target was an SPF of 50. We used the recipe ourselves and on our kids while outside in Houston Texas Sun. At the park in temperatures over 100 we didn’t want to stay out long, but after 30 minutes of rigorous play no one showed any signs of skin redness or sunburn. We also tested wearing the sunscreen in the pool. We designed our recipe with the intent for water resistance, however we didn’t do anything to test for it. We applied the cream only once before enjoying our fun outdoor activities and we stayed in the pool at least an hour each time. With all that said, If you are going to use our DIY sunscreen product, I’d recommend you apply it at least once every 30 minutes.
To further test if our products actually block UV rays, we purchased some UV sensitive beads and sun print paper. Obviously these materials don’t work the same way our skin does, but they do respond to UV rays immediately and in a visibly way. The beads darken, becoming purple when exposed to UV rays, while the paper lightens until it’s white or almost white.
For this test we used several top recommended sun screen brands and coated our materials in the cream, then took pictures every 10 minutes. The results surprised me as we conducted this test multiple times and each time two of the creams failed to have any noticeable effect. The one cream besides our own that did work use’s extremely toxic ingredients.
These experiments were taken on different days with different levels of cloud cover, but the box was left out in the sun each time. I took 1 picture inside then 1 picture as soon I placed the box and after that I took pictures once every 10 minutes and as you can see our sun screen kept the beads white or very light. Hello bello and babyganics had disappointing results especially in the test that was conducted under clear sunny skies. The beads coated in their sunscreen darkened almost immediately. Blue lizard's sunscreen did a good job of protecting the beads however it contains several highly toxic chemicals including carcinogens which I find ironic and shocking since the primary purpose of sunscreen is to help prevent cancer.
See the photos here