"At the end of the day, put on sunscreen" -- uhhh wouldn't it make more sense to put it on at the beginning of the day? 😀

What would've been cool is if you'd filmed in UV the affects of going in water with sunscreen on, or maybe a time lapse to show how much it fades throughout the day.

I had a discussion not long ago where I was in favor of including UV cameras in cell phones for creative purposes and others saw no benefit to having them. This would be a great use for them, you could see if you had applied your sunscreen properly.

I have always heard the two sunscreen categories described as "chemical" and "mineral." I don't think the chemical bit is an intent at scaring people. It's just descriptive of how the sunscreen works. When in the video they say that these types of sunscreens "absorb" the UV light, what they really mean is that the UV light induces a chemical reaction within those chemicals, where they are broken down into smaller molecules. By giving energy to the chemical reaction, the light becomes less dangerous, and its frequency shifts down so that it is mostly heat rather than penetrating rays. And this is why they say you have to reapply the sunscreen every few hours: the chemicals get consumed as they work. They also get consumed if the sunscreen in left in a hot location, so it's best to not leave your tube of sunscreen out in the sun when you're at the beach. The mineral sunscreen, on the other hand, are physical barriers that are placed between the light and the skin. No chemical reaction takes place (or only a tiny one). The light simply bounces off it. This is also why you can generally see mineral sunscreens on people's skin. It's an actual physical barrier. But they also make tinted varieties that are less noticable. Both chemical and mineral sunscreen contain chemicals that are potentially toxic to some degree. The chemical sunscreens we use in the US are banned in Europe and vice versa. (But this might also just be protectionism because the chemicals in European sunscreens are produced by European companies, and the US sunscreens' are made by US companies). However, the molecules in mineral sunscreens are orders of magnitude larger than those in chemical sunscreens, and the latter get broken down into even smaller ones. So the chemicals in chemical sunscreens are much more likely to make it into your bloodstream than those from mineral sunscreens. Regarding effectiveness, my understanding is that the chemical ones tend to work somewhat better, although they need to be continuously reapplied because the UV light is constantly breaking them down. With mineral sunscreens you also have to make sure that they have BOTH zinc oxide and titanium dioxide in them, as the two minerals are effective against different light wavelengths. My personal sunscreen strategy is to use a mineral sunscreen as my every day walking about sunscreen. I mix an untinted and tinted so that it matches my skin color. If I'll have a long sun exposure, then I have a sunscreen that is primarily mineral but also contains some of the chemicals. To me that seems the best tradeoff between safety from the sunscreen vs safety from the sun.

I love how on the day we filmed this I got sunburned because I couldn't wear sunscreen or else it would show in the UV camera. I like that my stealth filming of you telling us how you really feel made it into this video. Also, why do I look so serious? Happy Physicsing Dianna!!

One thing I'm surprised went unmentioned: "SPF" is defined by a testing method, where the SPF number is the threshold of how much UVA/UVB doesn't make it through the product (applied in a standardized layer). It's a very simple bit of math! SPF 4 = 1/4 or 25% of the radiation is not blocked (absorbed/reflected) SPF 8 = 1/8 or 12.5% SPF 15 = 1/15 or 6.7% SPF 30 = 1/30 or 3.3% SPF 50 = 1/50 or 2% SPF 100 = 1/100 or 1% SPF 150 = 1/150 or 0.67% So it makes good sense that you can't readily tell the difference at higher SPF's because the difference is getting tinier and tinier. The difference between SPF 15 and 30 is 3.4% radiation getting through, but the difference between 50 and 150 is only 1.3%. This is also interesting in terms of evaluating the UV camera's receptivity, because SPF doesn't discriminate between how it gets results (absorbing vs reflecting), but the camera is registering the UV radiation emitted/reflected, so as you observed absorption darkens and reflection may be invisible or actually lighter. So if you had two different brands achieving the same SPF value by different combinations of the two mechanisms, they may appear different on the camera even though they have the same efficacy from the skin's point of view.

I was super surprised at the spray sunscreen. I always thought they feel like they cover, but aren't covering as well as normal lotion.

I need a camera like this, so I can see if I put my sunscreen on correctly.

There’s a plant called Heracleum, which is pretty common in Russia (and the whole northern hemisphere if the Wikipedia is correct). It’s very invasive and grows very fast. If not destroyed it can cover very large areas very fast. What’s worse is that its juice causes severe burns. That’s common knowledge in Russia. A much less known fact is that those burns are not caused by juice itself. These are actually sunburns. The plant’s juice causes chemical reaction which dramatically increases skin’s photosensitivity. So it’s basically a reverse sunscreen. And those severe (sometimes even lethal) burns can be avoided just by covering from sunlight.

I don't get why people think inorganic is bad and organic is good. Poison can be organic as you can get it from snakes, scorpions and animals like that. Water is inorganic, air is inorganic. People really nead to understand what can do damage, to who and in what quantity. It's like I'd be against using peanuts for any purpose because some people are allergic.

Can’t help but sing “THE SUN IS A DEADLY LASER”

Stay strong Diana! We hope you feel better soon!

At 10:28 Derek says "At the end of the day, put on the sunscreen". Bad advice. I would put it on at the beginning of the day. :-D

the best sunscreen is staying inside to watch physics girl and veritasium videos all day

Uhmm I think FDA stands for “food and drug administration” not “federal drug administration” 4:56 I love the video though❤️

how to be a toxic person: Use reflective sunscreens, persuade your friends not to wear one, and give your friends skin cancer

Disappointed that no distinction was made between UVA and UVB.

OH MAH GARSH. Benoît, you are very correct. FDA stand for Food and Drug administration. Apologies for the error, all.

WOW where di you find all these people who are actually interested in learning something!!?? Well done!! Nature is AWESOME cool Vid!!

You should make another video and show us that how long does the sunscreen stays on your face specially in summer 🌞🌞🙃🙃🙃

SPF is also the noise you make when you accidentally open your mouth when spraying sunscreen on your face.

Thanks for helping us with our experiment and trying on the sunscreens, it was a blast!

Did you try smearing sunscreens on a clear filter and putting it in front of the camera lens? This seems like a better test of sunscreen effectiveness since reduced transmission is really what you want to test regardless of the cause be it, reflection or absorption. Sorry if this has already been proposed in the 2 years it took me to find this video. Love your channel!

Imagine putting on all those different sunscreens from weakest to strongest (In SPFs) on your arm and sorta blending them and making a gradient tanline that would be so cool

Isn't FDA "Food and Drug Administration" ?

Thanks, now I know which sunscreen to get.. Sharpie

Personally, I just wear a rash guard or spf rating long sleeve shirt. It'll keep me protected all day long and I only need to cover my face, hands, and legs with sunscreen.

What I got from this video is that I'd love to have an outdoor couch.

It's as bad as when people say they don't eat chemicals.

a better test for "physical" and "chemical" a piece of uv transparent glass coated with different sunscreens with uv source behind it and camera infront to see how much uv passes through

I feel like a better distinction would be sun (UV) absorbers and sun (UV) blockers vs the generic apply all sunscreen. I’m a bit confused as to why you seemed hesitant to the sun blockers (zinc oxide and titanium dioxide). I’m disappointed there was no distinction between UVB and UVA. We need to have better UVA blocking sunscreens. Edit: Change a UVB to UVA. On a mobile device. Apologies.

Maybe it’s just because I’m ghostly pale, but I definitely have found that a higher spf is less likely to turn me into a lobster 😂 I’m going to stick to my 100+

tfw you're subscribed to both channels and don't know which to watch first, so you just freeze and sit there looking at your sub box

Organic would be an even worse name than chemical, but in the other direction. "Chemical" has negative connotations and "organic" has positive connotations. In both cases, the connotations have zero to do with the actual definition of the word though.

zinc oxide: reflects uv lights

Cool videos! I also love the breakdown of inorganic (physical) vs. Organic (chemical). However, SPF is a Transmissive parameter and you are looking at reflective properties with the UV camera. Can we try this with Quartz glass & sunscreen to see how well UV gets through to the other side of the glass?

I just want to know what happens if you spray sunscreen on a solar panel. Would it still work as well?

3:55 Dianna is making a mistake here not acknowledging gamma compression in grey scale values. Our eyes just aren't made to distinguish linear value changes so that part of the scale gets compressed. Just because it LOOKS like there's not much difference between 50 and 100 doesn't mean that the 100 isn't ACTUALLY twice as dark.

Call them absorptive and reflective: Boom goes the dynamite.

No sunscreen=cancer Sunscreen=cancer Lol

there is no spf 100 here in Europe, at least I haven't seen anything like it here in Portugal...

9:39 And that's why it is important to spread scientific literacy as much as possible. Thanks Dianna for your work! (and thanks Derek also, I'm a great fan of him as well)

Dianna's face at 9:40 (holding almost perfectly still for 11s) is everything!!!

Good video guys, I like the aspect that you are supporting talking about the actual dangerous fact but separating it from the science and giving people that informantion... really appreciated, I like the work put in.

@4:55 - FDA stands for Food and Drug Administration.

The title card for the video, with Dianna's face split down the middle between UV and visible light, is a work of art and would make a great poster.

Nice video, I do wish however that you would have explained what spf means in more detail, how it correlates to time, and maybe how it protects against UVA better than UVB and what that means. Also, maybe coming back an hour or so later to see how the different sunscreens have lasted over time could be interesting.

I love the “happy physicsing” tag line. Say it with pride Dianna. You have a lot to be proud of.

Woah didn’t veritasium and how to make everything make a video similar to... Oh it’s alright I saw them on... this is intentional.

Spray sunscreen doesn’t seem to make much sense because you are essentially protecting your skin at the expense of your lungs.

You should have tested the sunscreen wear over time. The point of high SPF is that it remains effective for a longer period than lower SPFs. Most people don't apply (and reapply) the recommended amount anyway. Higher SPF helps in that, even if you are applying insufficient amount, you're getting at least SPF 30 or 50 from a sunscreen labelled as SPF 100

Brilliant video! Learned a lot. We need more people to make videos like this on other important topics. Luckily, there is more and more information about sun damage and sunscreen in general. As an aesthetician I am wearing sunscreen every day! You get only one skin after all. I also don’t smoke nor drink as much anymore. I’m 27 and I’m really taking care of myself now. The only thing I do, which I should definitely stop, is eating junk food from time to time. It’s like my guilty pleasure! :D It’s not okay. Love the video!!

The chemical discussion here reminds me of a time I did a "science project" for school where I made molecule shapes out of toothpicks and marshmallows. I didn't want people to just eat them while they were unattended, so I just put a note on them that said "don't eat, contains chemicals".

6:37 I've traveled to Redang island more than a decade ago, we were told to not use sun screen so that we dont destroy the ocean ecosystem... it seems like someone had the foresight

Great video! If you would like to avoid using sunscreen and sun burn I recommend long sleeve outdoor shirts, long pants and a wide brim hat. I live in southern Arizona and even in intense heat this works great.

This is pretty interesting about sunscreens. I'm glad they mentioned the mineral sunscreens which is my preference. Not just for the health reasons that they discussed as we learned that some of these sunscreens that absorb light versus the mineral that reflect, it have been shown some to enter the bloodstream and be bad for the coral reef. But as someone if you has done 10 hours in the 🌞 of biking many times in her life there is quite a bit of sun damage on my face and shoulders, arms, hands. On my face when I go into the sun I can see the sun damage kind of pops out and it looks like I have freckles. 9vertime that dissolution sticks around even when il out of the sun. When I wear a mineral sunscreen I find that I get better protection and that does not happen. I have also found that I've been getting less pigmentation from the Sun. I also prefer to find an SPF clothing now when spending high amounts of time in the sun like biking or hiking. And if I was a swimmer I would probably get one of those long sleeve spf bathing suits. I am curious what these spf clothing looks like under the light

"At the end of the day...put on sunscreen." - Or, maybe, put it on at the *beginning* of the day when the sun is coming up?

I like that there wasn't a single mention that they're doing a collaboration While still doing it WOW

I've already discovered the ultimate sunscreen - staying indoors.

I realize just now that every summer, without anyone knowing it, im secretly doing blackface ... 😲

Why didn't you apply reflective (and absorbing) sun screens to transparent foil (transparent in UV) and check its shadow?

As a chemist, what I can say is that inorganic UV filters must be in the form of nanoparticles in order to refract UV light. But the size of nanoparticles is very important because although smaller nanoparticles diffract UV light better, they can be absorbed by the skin more easily and at the moment there's not enough studies on the effects of absorbed nanoparticles such as zinc oxide or titanium dioxide. Moreover, nanoparticles of titanium dioxide are known to catalyse, as a result of UV radiation, the production of peroxides and radical species in aqueous environments that can be very harmful to cells. With this in mind, the size of nanoparticles must be established and regulated by law very accurately. As far as organic filters are concerned, most molecules contained in sun creams are based on natural compounds with known UV light absorption activity. That's why many creams have a slight carrot aroma for example.

The perks of SPF 50+ is that in France the UVA protection has to be at least 1/3 of the SPF, so between SPF 30 and SPF 50+ the UVA protection is really different !

"Physical" sunscreen sounds pretty great, both because its reflective nature means it won't make you feel so warm, and because its inorganic nature makes it less likely to interact in negative ways with organic creatures like coral reefs or our own bodies (although that's not guaranteed; asbestos is inorganic and I try to limit my exposure to that!). But I've also read that it doesn't stay on your skin when you swim or sweat, and it's hard to avoid sweating when you're in the sun.

I've had skin cancer (caught early, fortunately) so I'm very protective of my skin when outdoors. I prefer to use UV-blocking clothing, wide-brim hats and gloves, but I do use sunscreen sometimes. I don't want to use sunscreen often because I don't know what long-term use will do to my health. People forget that the skin is the largest organ in the body. I figure that clothes are "safer" than topically applied chemicals. I have a photo taken of me a few years back fishing from my kayak, and you cannot see any skin at all--I have 100% coverage (including my face).

I love "Happy Physicsing"!!! It is very cheerful and helps to take away the stigma associated with most science and engineering.

Still here to support one of the greatest content creators on this platform!!! Love and miss you Diana

Great video, Diana! I really hope you get better soon. I have PASC/Long Covid too, and it is so hard. Together people with this condition will get through :)

If anything warrants a second episode it's this. Loved the vid and would love a deeper dive in the currently used elements in sunscreen. Both from a biochemical and a (bio)physical lens. Do the 'physical' sunscreens have similar issues with the oxides as with the aluminum oxides that are used in some deodorants? Is it effective to combine the 'physical' and 'chemical' sunscreens? What possible environmental impacts are there? What research/actions have been prompted by the recent findings? There's loads to look into.

Hi, interesting video! However, a more rigorous measure would be comparing transmittance instead. You can do it on glass with a control sample. Would be interesting if you can have a good control of thickness, and measure the results with different thicknesses too.

I just came across your videos, they're so informative and cool! Love your enthusiasm!

LOVE your channel and all of your vids! You ROCK!

That was an interesting video. As someone who has had several skin cancers and now has to go in to the dermatologist twice per year for a skin check, I can vouch for the fact that skin cancer is no fun. Use sun screen boys and girls.

Happy to see both together . I'm a big fan of both channels

I appreciate how they actually use a real study and not an article as media tends to oversimplify and assume a lot of results of academic studies

I've always wondered why I get more sunburnt when I put on sunscreen. Cool to know that there is reflective sunscreen as well, I am gonna start looking to use those ones.

I love it! I'm currently on a vacation and I literally researched the same things for the first time this year and got totally confused. Love you made this video, just what I needed for my own peace of mind 😊

I'm not so surprised that the effects of sunscreen on the environment (e.g. coral) aren't so well known. What I am surprised at is that Hawaii is going to take 3 years to ban certain sunscreens. I just don't understand what part of the ban should take so long when they know it is causing damage to the coral.

You could also simply use a UV lamp / or the sun and then have your uv camera in box and then compare the light that the camera capture through a filter where you aply the different sunscreens rather than looking how dark or not the skin looks.

Always does my mind joy to have two of my fav youtubers in the same video.

The paper on skin absorbance of sunscreens concludes its abstract with: "It is concluded that the human viable epidermal levels of sunscreens are too low to cause any significant toxicity to the underlying human keratinocytes." You implied to the viewer that the study says it the sunscreen ingredients are dangerous.

What a great day. Physics girl and veritasium notifications at same time.

Love you Physics Girl!! Please get well soon! ❤💐

Very well explained! I'd just add that chemical sunscreens are more likely to be irritating to some skin types. I have to use mineral sunscreen otherwise I get a severe rash. Mineral sunscreens often create a white cast though, so I use tinted.

"Ladies and gentlemen of the class of '97: Wear sunscreen. If I could offer you only one tip for the future, sunscreen would be it. The long-term benefits of sunscreen have been proved by scientists, whereas the rest of my advice has no basis more reliable than my own meandering experience."

It would be so cool to hang out with Derek and Dianna

Thanks Diana. You do such an important job so very well.

Enjoyed this, and I love Physics Girl and Veritasium, but I'm a bit disappointed they didn't mention sunscreen should be the last line off defense. Most dermatologists say to wear sunscreen, but also to use shade and protective clothing (hat, swim shirt etc) as your first lines of defense against the sun.

Was expecting this video to show how the sunscreen degraded over time under the UV camera but it only showed how dark it was on initial application :(.

Zinc oxide works the best as sunscreen. 50 plus last the longest. Just remember to reapply.

I clicked on this video wanting to watch people draw pictures on themselves with sunscreen but I actually learned something so thx ig

UVA Rays and UVB Rays are both blocked by sunscreen, but UVB Rays are blocked at a far lower rate on sunscreens SPF 50+

I love this video! Thank you for making it. A grammatical note: "begs the question" does not mean "raises the question." "Begs the question" comes from formal logic and is a logical fallacy wherein the speaker uses the premise to support itself.

I am really learning on this video. Kudos guys!

I saw you had some oils there, did you test them aswell? I'm so curious to see if raspberry and carrot oil can actually be used as spf

Thank you for sharing your work. I would like to see a similar video comparing "regular" clothes and "UV Protective" labeled clothing. Do the UV labeled clothes provide more protection?

When strictly speaking about the camera method of checking the UV protection you have to keep in mind that the absorbing sunscreen absorbs TWICE. This is something that you didn't adress in the video, I don't know if you've factored this in. But essentially the sunscreen lets through a small part of the UV light and absorbs the rest, and when it reaches your skin again some part is reflected and absorbed. When you get to factor 50+ it becomes hard to tell from a camera if the light had been absorbed once or twice (meaning maybe the 100 factor sunscreen absorbed almost all of the UV light the first time around, and the 50 factor one only absorbed some first, and some more on it's way back). I hope I'm being clear in what I say, I'd be interested to hear back if you factored this in.

As a person with the least melanin, other than sufferers of albinism, there is a BIG difference between 50spf and 100spf. Not many of us can get burned at sea level with 50spf, but me and my son do!

Yay, two favourite KZfaq Derek and physics girl

Veritasium and the tumbnails matched in my subbox D: