Mineral SunscreenPosted by Kalon on October 27, 2022 at 7:05 pm
I want to formulate a sunscreen with only zinc oxide and I will be using pre dispersed zinc oxide
I have these problems
1. How much zinc oxide to use for SPF 30 ?
2. How much zinc oxide to use for SPF 50?
3. Also how do I add a mattifying effect in sunscreen don’t want a hydrating sunscreen.
I’ll be using 20% zinc oxide dispersed in iso-octyl palmitate
I cannot afford to make SPF and then run on testing again and again for different SPF I can only take once and run on a professional SPF testing in my country
MemberOctober 27, 2022 at 8:09 pm
I am sorry if this comes rude to you, but if you don’t know how much Zinc Oxide to add to achieve a specific SPF, I don’t think you are ready to formulate sunscreens.
But to answer your questions 1 and 2 -
UV absorbance E max λ @ 1%/1cm is 280 - 370nm @ 1:0.75-1.
Therefore in extremely good base, 1SPF would be approximately 1% w/w.
Then you can calculate how much of your ZnO dispersion you would required to achieve desired SPF. (And hopefully you already see the problem)
I don’t think I really understand your third question, but if I do, I don’t have answer for you. You would probably need to test it as we don’t know anything about your formula.
MemberOctober 28, 2022 at 1:27 am
If you have access to SpecialChem that may be a good place to start. Or look at similar products already on the market and see if they advise how much Zinc Oxide to use (though they probably also do not want to commit a % for actual SPF). I wouldn’t attempt a sunscreen for commercial use unless you really know what you are doing though.
Here is link if you have access - Starting Point Formulations – Cosmetics and Personal Care Products (specialchem.com) - If you dont have access your company may be able to join? Good luck.
MemberOctober 28, 2022 at 6:54 am
Thankyou so much for your suggestions. I’m formulating it for myself as I’m tired of using extra hydrating sunscreen in the market which leaves me with acne on my face, also I don’t like the feel of chemical sunscreen:(
Also in the third question I was asking what I can add as an ingredient in the sunscreen which would leave my skin matte and not hydrated, I find that extra hydrating ingredients clog pores
MemberOctober 28, 2022 at 8:50 am
Hehe, still confused. You’re saying you’re formulating extra hydrating sunscreen but after that you say “leave my skin matte and not hydrated” ..
But I guess I know what you mean.
You need to be careful with what else is in the formula and what type of lipid you’re using. You would need to share your full formula.
(I’m not familiar with iso-octyl palmitate)
PS. Look at your ZnO dispersion. It is 20%. So if you use it neat on your skin, you could get maximum (if) SPF 20. Now, you won’t be using it neat right? Therefore you cannot even reach SPF 20.
Formulating sunscreens is not easy. You need to take care about a lot of aspects - stability, homogeneity, coverage on the skin … if you don’t get full coverage it’s almost pointless to use sunscreen as you will still have areas when the sun “hits” the skin. I hope you understand.
Anyhow, happy formulating!
MemberOctober 28, 2022 at 9:09 am
Thankyou for your response as I mentioned above hydrating sunscreen leave me with acne so I’m trying to formulate a sunscreen which leaves my skin matte at the end and not hydrated.
Also I’m getting enrolled in a cosmetic chemist program soon so I’ll be learning loads there , just wanted to experiment myself first ☺️
MemberOctober 28, 2022 at 11:24 am
As @Paprik mentioned, there are so many things to take into account when formulating a sunscreen, even experienced formulators could miss some things, so I would advice to to experiment with a different cosmetic, and you can leave sunscreens for when you finish your program.
MemberOctober 28, 2022 at 11:27 amHey!As I understand it, you want the final effect of the product to be matte and not shiny on your skin, right? Well, this shine is not necessarily the same thing as hydration (even many products can be shiny AND have a dry feel). Because they are two different things, I suggest you first define what your priority is: making a product that doesn’t shine on the skin OR a less oily product. Doing both at the same time can be more complicated.As for the FPS, I don’t know if this helps you, but BASF has a system where you can find the ingredient-percentage-FPS-PPD ratio when building your formula there. The link is this one. It’s been useful around here a few times and it’s a good guideline.I particularly suffer from the same problem with sunscreens, it costs a lot to adapt… but you can try a stick or an oil-free version, if it suits you. The result may not be as good as an emulsion, but as the pros say, “the best sunscreen is what works for you, and any is better than none”… just make sure your product is safe and effective.
MemberOctober 28, 2022 at 6:01 pm
Thank you so much for the great info.
MemberOctober 29, 2022 at 12:38 am
Hi not sure where you are based but maybe look at brands that work for your skin. I found this place (based in Hong Kong called Stylevana ) and if you buy over I think $60 (AUD) shipping is free to Australia (plus you get $10 off your first purchase) Shop SUNTIQUE - I’m Safe for Sensitive Skin SPF35 PA+++ - 50ml | Stylevana - It is certainly the best face product I have found for a reasonable price is AUD compared to anything I can buy like this in Australia. They are a number of Sunscreens here so you may just want to look to see what ingredients are in their products. I have now bought this one which is ‘safe’ for sensitive skin and it goes on so smoothly and no white residue etc and no problems with my skin using it (I have Rosacea so I am careful about what may cause a flareup- using this and making my own skin creams I have been flareup free for about 18 months now). Also look at the INCI decoder for any products you think you might like to try - so this is the list for the product I now buy (which I could never make in a blue moon) : Suntique I’M Safe For Sensitive Skin ingredients (Explained) (incidecoder.com)
Hope this helps or give you some ideas. I think until you do your course though it will be cheaper and safer to buy sunscreens for now.
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