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Formulating face creams with pH in mind
How important and what is the effect, long-term or not, of formulating a face cream at a final pH of exactly 5.5 to roughly match the skin pH as opposed to shifting to a pH of closer to 6-6.5 to benefit more from the thickening effect of carbomer materials? The contradiction between skin pH and optimal carbomer pH for maximal viscosity has resulted in me wondering whether to just use Structure XL instead, a starch based thickener.
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8 Replies
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When i use carbomers or other Ultrez i tent to leave the pH at around pH 4.8 to pH 5, slightly above the pH for gelling so personally i’m not that bothered by what you are mentioning.
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I’m bothered by it because there is a significant viscosity increase above ph 5.
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Then perhaps increase the percentage of the carbomer you want to use?
Using a starch might challenge the preservation system more than you think and the cost may be higher than just increasing 0.1% to 0.3% of carbomer.
The pH would still depends on what your requirements would be. If your intention is to make a cream that is “pH balanced” or if it’s meant to stabilize certain actives, then it’s best you stick to it.
Choose a logical or cost effective option.
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Hydroxypropyl starch phosphate; this is a very processed starch product; would this challenge the preservative blend?
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Normally i’d consider using a starch if i want to degrease or give it a drier / powdery skin feel.
Maybe you can list the preservation system you want to use,the percentage of Hydroxypropyl starch phosphate you want to use and see what feedback others might give and
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Some preservatives do not work at such a high ph as 5.5.
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The preservatives I use do work above pH 5.5
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My preservation system: Phenoxyethanol/Phenylethyl alcohol (0.7%), hydroxyacetophenone (0.2%?), sodium benzoate/benzoic acid (0.4%?), 1,2 hexanediol (2/3%), +tetrasodium glutamate diacetate (not sure inclusion rate for this one, maybe 0.2%). Structure XL: 1.5%
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