Ellen Barrett's Homemade Sunscreen!

[DawnP]

I have a bone to pick about how Ellen calculated the final SPF of her sunscreen. She states the SPF of 3 of the ingredients, then adds them up to get the final SPF of her sunscreen product.

· ½ cup almond or olive oil
· ¼ cup coconut oil (natural SPF 4)
· ¼ cup beeswax
· 2 tablespoons shea butter (natural SPF 4)
· 2 tablespoons zinc oxide (natural SPF 20+)
=====================================
= SPF 28

That's not correct. They don't add opacity cumulatively, they actually dilute each other out. It would be like saying 'if I add 24 proof rum to 5 proof wine, I'll have 29 proof (stronger, more concentrated) liquor'. Tee hee.

If you use the zinc oxide mfr's guidelines here, the final product has an SPF of about 5 or 6.

Can I have Jennifer or one of my chemistry/pharmacy geeks double-check my math?
I'm going with each tablespoon of micronized zinc oxide powder weighing 5.4g. Total preparation at is 300gm. Final wt/wt % is 3.6%. According to the table shown in my link, 3.6% correlates to an SPF of about 5 or 6. I kind of neglected the SPF of the coconut oil and Shea butter. They likely don't change the final SPF much.

Even this more concentrated recipe only results in an SPF of 11 or 12.

Man, I need some better hobbies.

[adawn]

Thank you DawnP for the math. It’s always nice to see real life applications. I hope someone is able to double check your work (I am sadly not a chemistry/pharmacy geek).

And while making your own sunscreen has its advantages, not all commercial sunscreens will burn your eyes and have that distinctive day-at-the-beach sunscreen smell. I use Vanicream sunscreen (sport SPF 35) which has no scent and doesn’t burn my eyes, even when forehead sweat drips down and I rub my eyes (I also wear contacts).

I’ve been consulting the EWG sunscreen guide for several years.

I also wonder what kind of UVA (broad spectrum) coverage Ellen’s recipe provides. Seriously, I have no clue about this and want to know. I actually don't even wear any SPF products most days because I figure I need what little sunlight I get running errands and such. But when I do wear sunscreen, it's because I need the protection while outside all day with a high UV index.

I should add that I don't mean to be a debbie downer, because it is cool making your own skin products from scratch.

[Leonana]

OT: I like her kitchen. I've always wanted white cabinets and granite countertops {sigh}

[paideiamom]

I am going to try it without the zinc oxide for just a moisturizer to see if I like it.

I, too, am a fan of the spray for the lightness of the touch and effectiveness of coverage.

[aunatural]

Thank you. I also thought Ellen's video was a tad too simplistic. I researched natural sunscreens a few years ago (even found a study that suggested rubbing a strong enough dilution of green tea on the skin provides UVB protection) and concluded that for prolonged sun exposure, something created in a lab is probably the best option. There are tons of more natural sunscreen options on the market now and as a black woman, I do not like the white tint that oxides give my skin. Love Ellen but I would just rub on some straight shea or coconut oil if I don't plan to be outside very long. SPF 8 is enough protection for light sun exposure.


[/B]

Originally Posted by adawn

Thank you DawnP for the math. It’s always nice to see real life applications. I hope someone is able to double check your work (I am sadly not a chemistry/pharmacy geek).

And while making your own sunscreen has its advantages, not all commercial sunscreens will burn your eyes and have that distinctive day-at-the-beach sunscreen smell. I use Vanicream sunscreen (sport SPF 35) which has no scent and doesn’t burn my eyes, even when forehead sweat drips down and I rub my eyes (I also wear contacts).

I’ve been consulting the EWG sunscreen guide for several years.

I also wonder what kind of UVA (broad spectrum) coverage Ellen’s recipe provides. Seriously, I have no clue about this and want to know. I actually don't even wear any SPF products most days because I figure I need what little sunlight I get running errands and such. But when I do wear sunscreen, it's because I need the protection while outside all day with a high UV index.

I should add that I don't mean to be a debbie downer, because it is cool making your own skin products from scratch.