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Preservative % for Small Water Phase
Hi! I’m working on a lip balm product with 4% water and 3% glycerin, the rest of the formulation is oil soluble. I know that I need to incorporate a preservative, but not sure how much is needed for such a small amount of water, as this is my first time formulating something like this. I’d like to use Liquapar ME (phenoxy, methylparaben, ethylparaben, caprylyl glycol) or Euxyl PE (phenoxy, EHG). I know it’s impossible to give concrete percentages, but any guidance would be so appreciated!
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10 Replies
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I have been taught that ≤5% water, which should bring the available water ( a<sub style=”background-color: var(-bb-content-background-color); font-family: inherit; color: var(-bb-body-text-color);”>w </sub>) to <0.6, should inhibit any microbial growth. However, if there is a chance that water will be introduced, I would use those mentioned preservatives at low recommended inputs.
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I’m assuming the ratio of glycerin to water is also lowering the water activity, but since it’s going to be in contact with moisture on the lips, I’d like to play it safe. I don’t want to incorporate too much preservative though as it will change the texture of the formulation, so I’d like to go as low as possible while maintaining preservation.
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Should i assume this is a water in oil emulsion?
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It’s an anhydrous base with the water/glycerin incorporated using Polyglyceryl-2 Diisostearate.
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What is composition of aq. mixture?
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4% Water, 3% Glycerin
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No - the composition of the aqueous addition - 4 parts water to 3 parts glycerine?
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Oh sorry yes - the aq. phase is 57.1% water, 42.9% glycerin.
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That’s the only water in your product. If you water quality is good, you will have a small weakness vs fungi.
Do you control its pH?
Assume you’ll not try to challenge test.
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and water activity is not based on water % short of anhydrous. 4% has to be controlled.
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