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    Hey guys, I know Marie wrote a post about this, but I’ve provided a (somewhat) shorter version here for anyone who wants a quick read about why DIY sunscreen is a bad idea. Feel free to copy and paste when answering other’s inquiries about why they should stop making sunscreen by hand! (but i’d appreciate a credit if you do)


    There are two categories of SPF: chemical and physical.

    The chemical SPF includes ingredients such as oxybenzone, which works as a light absorber (diffuses the UV-A and UV-B rays to reduce the energy of the rays before they reach your skin) — it’s called a sunscreen. I’ve yet to find a place where someone can purchase oxybenzone, and the compound is volatile by itself so it’s probably a bad idea to try and DIY with it.

    The physical SPF uses zinc oxide, which is very tricky to use on a molecular level — and it’s called a sunblock. In order for zinc oxide, a light-reflecting SPF, to be 100% functional, the powder needs to be completely evenly dispersed within the base (or matrix) on a molecular scale. This requires equipment to use sound (or sonic) waves to vibrate the particles into the matrix instead of clumping together. This equipment starts around $200 for a small-scale laboratory. Then it needs to be tested in order to determine which SPF it’s effective at (ie does it block 95, 96, or 97% of UV-A and -B rays?), which costs at lease $700 in most labs. Without the sonic vibrators and testing equipment, you literally have a 0% chance of knowing if you’re blocking BOTH UV-A and UV-B rays (once which causes cancer, the other which causes tanning).

    In essence, sunscreens and sunblocks are very difficult and expensive to manufacture, which is why you don’t often see very small cosmetics or skincare companies making them.

    If you’re looking for a good place to get sunscreen or sunblock, I recommend brands like Neutrogena and Badger Balm, respectively.

    Hope that answers your questions! PS, I’m a professional chemist, so I’ve studied up on this extensively.



    This is fantastic! Thank you so much, Sarah!


    Also, here’s some extra info about “chemical” sunscreens from Badger Balm, who has a very in-depth post about the science of sunscreen and light dynamics (seen here and here):

    Sunscreens such as avobenzone and oxybenzone have a very limited range of light wavelengths that they work on, meaning you need to use a larger assemblage of similar sun screeners in order to achieve a broad-spectrum sunscreen. Also, SPF only refers to the amount of UV-B rays that are blocked, and UV-A rays are the cancer-causing ones. So Broad Spectrum (or UVA-PF PA ++ grade or higher) is necessary!


    Thanks Sarah!

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