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This isn’t the first time a natural sunscreen I’ve purchased has split :(

November 22, 2014

I am ALWAYS working on Zinc based sun protection products and while I have a couple of formulations that are stable I’m still struggling (if I’m honest) to create something natural and light. My formulations feel a little heavy but at least they are stable…….

I visited my local health food store this week and purchased two more SPF 30 zinc based formulations to add to my collection and further my research.  Today I got a chance to play with one of them and I wasn’t happy.  I’m not going to name and shame the brand as that is not my remit but what I will do is email them with the information that I am going to share with you below in the hope that you might recognise what a sunscreen based on zinc that is unlikely to meet its stated SPF rating might look like.


Commercial Zinc Sunscreen that has separated during its shelf life

OK so the above demonstrates what happened when I squeezed some product out of the pack. This wasn’t the first squeeze, this was a bit later on which is significant as it shows me that the product is severely leaking from the emulsion.  It is probably oily water coming out of the internal phase but I’d have to run a few more checks to be sure.  In any case it shows me that this product is not particularly stable – the expiry date on the pack is June 2017 and it is currently November 2014 so that in its self is telling as a sunscreen usually has a maximum shelf life of three years and usually 30 months is enough (2.5 years).  Well 30 months from now would be June 2017 so it has probably just been made.

Sunscreen glass slide


OK so a bit of leakage doesn’t necessarily mean that the world is falling apart so I wanted to see what was going on at a closer level as that would enable me to work out if the product was still likely to protect me from the sun or not.  I prepared a rough slide for my microscope and immediately saw something worrying – those balls of zinc.  In a professional lab we use a tool called a Hegman gauge  to look at particle size in pigment dispersions but for these purposes a glass microscope slide is just as good!

Visible lumps like that mean that the zinc is agglomeration and as agglomerated zinc can’t create a fine barrier across the skin this is the best evidence so far that the sunscreen will be defective.  I’ve been in tears of frustration over formulations that have shown much less agglomeration than this.  As I can have a closer look I did and this is what I found:

Sunscreen failure commercialised product

The green arrows show just some of the holes in the film, holes where the UV get’s through.  Zinc and Titanium based sunscreen filters work by leaving a thin film of particulate across the surface of the skin.  This film reflects sunlight so it bounces off, away from the skin thus preventing sun burn or tanning.  Because of this the key to creating a good physical sunscreen is creating a solid barrier with no holes. These holes act like lenses becoming a focal point for the UV that didn’t get bounced back and leading to the exposed skin getting a heftier dose of sun than it would have otherwise received.  Taking that to its logical conclusion we could say that a poorly formulated zinc or titanium based sunscreen is worse than nothing at all.  That is a disaster!

The red circles show the zinc clumps. Zinc is a super charged particle which loves nothing better than creating gangs of like-minded particles.  Such is Zinc’s pulling power that unless you have a super strong emulsion the zinc will seek out and befriend as much zinc as it can until you end up with what looks like cottage cheese.   Not good at all.

The bottom line is that the product that I paid $25 for won’t do what it is supposed to and because of that I am sending it back.  The question for me is, do I dare look at the other one now……

Happy Formulating.

Amanda x

4 Comments leave one →
  1. Cass permalink
    November 30, 2014 12:42 am

    New reader here.. So far I’m really liking your blog and it is really cementing my interest in cosmetic chemistry. Do you think there is any chance of someone who (will be studying for an) environmental science degree (next year) can ever be able to work in a cosmetic industry?
    I also wanted to ask whether there is a difference between ‘micro ionised’ and ‘nano’ with regards to sunscreen labels? Some even list ‘non nano micro ionised zinc oxide’ as an ingredient. Does that mean the particle size has been reduced but to the size of nano particles?

    • RealizeBeautyEd permalink*
      November 30, 2014 5:40 pm

      Hi there,
      Glad you are liking the blog. I can’t see why you wouldn’t be able to join the cosmetics industry at some point in the future if you are interested – you might have to do a bit of study in cosmetic chemistry if you want to apply for a lab job as a formulator but there are many other jobs that wouldn’t require that as a first step and could allow you a foot-in-the-door. I think you just have to keep your eyes open and look for opportunities. Linked in is a great way to build your network in that regard. As for sunscreens nano are particles that are less than 100nm in diameter whereas micronised are between 100-200nm. Anything larger than 200nm when talking about zinc oxide or titanium dioxide is really not relevant for sunscreen as the scattering that you get from the larger particle sizes makes the un-suitable for cosmetics. Nano particle size has to be listed in the EU at present but not in Australia.

      • Cass permalink
        December 6, 2014 9:22 pm

        Late reply 😉 Ooo that makes me really happy. I had all but given up on the idea. Actually I don’t think I really had. I’m unreasonably optimistic. I’m too starry eyed for my own good….

        Thanks for clarifying the sunscreen bit. So they are all technically nano particles.. Are the larger particles unsuitable because they don’t give a nice cosmetic finish? Or does there properties differ and they don’t offer the same amount of sun protection?

        Sorry for all the questions..I’m just really curious.

      • RealizeBeautyEd permalink*
        December 7, 2014 6:39 am

        FOr sunscreens we need ‘attenuation grade’ pigments rather than just regular zinc or titanium. This ensures that they are a grade that is able to protect us from UV light and not react with it and make the situation worse. The larger the particle size the lower the SPF per percent used usually and yes, with the larger particles you also get a whitening effect on the skin due to light scattering. This is less elegant cosmetically although it is possible to make a sunscreen with particles of around 200nm and have it ‘invisible’ 200nm particles are not classed as nano as far as the cosmetic industry is concerned. I’m not sure what other industries classify as nano and do remember that there are many ways of measuring particles.

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