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