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Soothing Serum Formula Check
Hi! Stephanie here, new to the forum - thank you all for accepting my request. Appreciate any help you all can give.
I am new to formulating serums and wanted to screen my formula for a soothing/moisturizing watery serum, below. I have very reactive skin so am moving away from anything super harsh and only going towards ingredients that have helped me personally. I am hoping to create a few for some friends too, but this is not for sale.
More specifically, I’d love to understand if the gluco/sodium benzoate will be enough preservative-wise or if there are other major callouts you have when making the formula (any pH callouts?). PS. I wanted to include Cucumber Distillate but thought that might be a fluff addition so I removed!
1% LMW HA (0.8 - 1.0M daltons) 1% panthenol 0.50% n-acetyl glucosamine 2.00% allantoin 0.50% glycerin 1.00% propanediol 1,3 2.00% hydroxyethyl cellulose 0.50% gluconolactone and sodium benzoate 1.00% green tea extract 1% centella asiatica extract 1.00% deionized water 90.00% -
13 Replies
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The preservatives you have chosen only work at low pH. What is the pH of your finished formula?
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@EVchem I haven’t tried the formula out yet but was hoping for 5 - 6. I also have Euxyl 9010 on hand here but I flush when I use phenoxyethanol so wanted to try a different preservative.
- Phenoxyethanol 90.0%
- Ethylhexylglycerin 10.0%
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You’ll probably want to add a small amount of citric acid to drop the pH to 4.5 - 5 for the preservative to be most effective; only way to be sure that it’s working is to get a challenge test done though.
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@LincsChemist
Thank you for your input! Do you recommend changing the preservative to something stronger if I am unable to do a challenge test? Copy on the Citric Acid though! -
I don’t think the gluconolactone/SB would be enough. I would make the pH6, and add a 3-5% niacinamide. Also I would use 0,3% HEC but that depends on what grade you have, so experiment with the %s and see what you like. Also Disodium EDTA is pretty much a must since you have some extracts. The green tea is very hard to stabilise so something like BHT is definitely welcome.
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@czkld
thank you! I will try HEC at .3%. I can’t add Niacinamide, my skin just doesn’t like it, but will definitely add the Citric Acid to lower the pH and then the Disodium EDTA as well.Question for you - should I just swap the preservative for a stronger one (reccos welcome) that way, I won’t need the BHT? trying to keep the ingredient list on the small side so i’m happy to cut what I need to in order to have a shorter list.
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@imopectore90 said:
Question for you - should I just swap the preservative for a stronger one (reccos welcome) that way, I won’t need the BHT? trying to keep the ingredient list on the small side so i’m happy to cut what I need to in order to have a shorter list.Preservatives won’t do much for the actual stability of the extract, so you would need an anti oxidant. And for green tea BHT is pretty much the gold standard (at least I think so)
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@czkld
This is what I have thus far - removed green tea extract while I wait for the bht to come in the mail. Let me know how it’s looking to you!1% LMW HA (0.8 - 1.0M daltons)
1%
panthenol
0.50%
n-acetyl glucosamine
2.00%
allantoin
0.50%
glycerin
1.00%
propanediol 1,3
2.00%
hydroxyethyl cellulose
0.30%
gluconolactone and sodium benzoate
1.00%
Citric Acid
TBD to reduce pH
centella asiatica extract
1.00%
deionized water
90.00%
Disodium EDTA 0.2%
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To me, looks pretty good, but again, I would change the preservative. I dont know if the panthenol would do anything, but thats a whole another topic. Also beware of the allantoin recrystalising
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@czkld
Thank you so much, appreciate it! LMK if you have any preservative recco’s that isn’t the gluco+sb. -
The reason I stopped using green tea extract (powder) was that almost all of it ended up wasted. I was using around 0.5% by weight, and after just three months, in the refri, it had denatured and become junk. I moved to pine bark extract instead, it has a similar profile but has been far more stable so far. Interestingly, they both act as indicators when used in cream. At the correct percentage use, and the correct pH, the emulsion resembles caucasian skin tone. Stability is an issue, more especially with the tea extract, since the initial tint is pink, but over time it turns to beige.
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@Belassi
Thank you for your explanation! makes perfect sense and definitely a reason to think through using it. -
Also for the thread, I’m going to change the preservative to Benzyl Alcohol (and) Benzoic Acid (and) Dehydroacetic Acid (and) Tocopherol. Will add citric acid if the pH is too high since this combo of preservatives works best at 3-6.
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