Preservative query for pH 7 cream

LuisJavierLuisJavier Member
edited December 2019 in Science
I'm using Carbopol 940 and I hope to use it at around pH 7 to really make the most of its viscosity potential instead of using more of it at a lower pH. I've found that Spectrastat OEL (caprylhydroxamic acid, ethylhexylglycerin, propanediol, caprylyl glycol) seems to fit in nicely with my desired product pH. I saw a comment from Perry indicating that a mixture of caprylhydroxamic acid, glycerin and caprylyl glycol (I think?) is quite a weak preservative system, so I thought, I could add phenoxyethanol to Spectratstat OEL and see where that gets me. Alternatively, I could just use Phenoxyethanol+Ethylhexylglycerin and a chelating agent like Disodium EDTA. My formula so far is as follows:

Water: 78.2%
Allantoin: 0.3%
Carbopol 940:0.3%
Glyceryl Stearate + PEG-100 Stearate: 3%
Propanediol: 3%
Peach kernel oil: 3%
Gosulin IL (Isoamyl Laurate+Isoamyl Cocoate):5%
Disodium EDTA: 0.2%
Shea butter: 1%
Aquaxyl: 1%
Niacinamide: 4%

Alternatively I could use the Spectrastat blended with phenoxyethanol, or the phenoxy.+EHG alone. If using Carbopol 940 at higher than 0.3% will not give me an oily/sticky feel like Sepimax ZEN does between 0.3-0.5%, then I do not mind using more Carbopol 940.


  • I use Euxyl PE 9010 (INCI: Phenoxyethanol (and) Ethylhexylglycerin) for my own DIY, i haven't not put it through testing since it's just for my own use. If you are concerned about alternative preservatives, it's best to use a more robust one especially if you are intending to selling it. 

    For carbomers, i tent to use Ultrez 10, 20, 21 since they hydrate faster, I've not yet used 940 or 980. For Sepimax Zen, it can be slightly tacky i feel, so i don't use it often. At 0.3% would be it more of a lotion viscosity?  
  • I've tested a batch of the carbopol 940 against the sepimax Zen and I think I agree with your sensation. I've not managed to get my hands on any other carbomer apart from Carbopol 940 as of yet - it doesn't seem so easy without contacting large companies. I just looked at viscosity differences between Carbopol 940 and Ultrez 10. Seems like Ultrez 10 has about 5000 units more viscosity-increasing effect than Carbopol 940. Not only that, I discovered that there are apparently benzene residues in Carbopol 940. Strange. Ultrez 10 seems to use other solvents for production. In regards to the preservative system, I think the Euxyl PE 9010 seems quite robust to be honest. I don't know what other kind of preservative system you'd recommend. I'm quite averse to using formaldehyde-releasers but I'm ok with parabens. Only problem with parabens is finding a supplier since parabens do seem to be undergoing a phase-out in the cosmetics industry.
  • I think I misunderstood your comment; I think you were referring to 'more robust' preservative systems as opposed to ones like Spectrastat OEL. 
  • To be honest, i'm not sure how robust the Euxyl PE 9010 is going to be but it still largely depends on the other factors, including the selection of ingredients, chelating agent usage, container, preservative boosters, and other hurdle factors. 

    I believe you also has a post on this: 
    Normally i'd just purchase my ingredients from China resellers (on Taobao since i have an alipay account and forwarding) in small batches which is about 200 of them out of my 240+?  Though sometimes i'd have my doubt on the authenticity of a few of the ingredients since normally i'd do my patch test with them and they don't seem to work for my skin but works for my relatives, so it's just very weird. 

  • What does Aw=0.80 mean?
  • I don't mind using DPG or MPG. I don't know how much of a preservative booster DPG is though. I would love to use Hexanediol but I need to find a good source and then buy some. Essential oils - I'm aware that clove bud and tea tree are quite effective, or at least somewhat effective. I don't know if I'd count on the EOs much though. pH 5 - that would be very tricky working with Carbopol 940. Chelating agent - phytic acid, zinc gluconate/sodium gluconate, disodium EDTA. 
  • jemolianjemolian Member
    edited December 2019
    I'm not certain what AW means since the image is from a comment from the MakingSkincare (on facebook), there don't remember one else asking about it when i saved it for reference. We will have to see what the others say. 

    Update, it would seem to mean Water Activity:

    For the essential oils, i don't think it's something that i'd use. But it depends if you want to go for an essential oil free product. Some people have sensitive skin so they may tend to look for something without additional additives like fragrance or essential oils. 

    If pH 5 an issue with Carbomer 940? Shouldn't they start to gel at pH 4.5 or higher?  
  • I think they might start to gel at around that pH but I think maximum viscosity occurs arround pH 7-7.5 so I don't think that the viscosity at pH 5 would be very good (please correct me if I am wrong).
  • MicroformulationMicroformulation Member, Professional Chemist
    edited December 2019
    Aw is your free water/water activity. If you go to the presentation from which the slide is captured, it explains further. Microformulation Cosmetic Consulting provides Custom Formulations for both large Commercial accounts as well as smaller entrepreneurs. We can provide Naturally compliant Formulations under the NSF, NPA, Whole Foods and USDA Organic Certifications. BS.Pharm Albany College of Pharmacy, Union University.
  • I advise testing your formulation using 940 but also with Ultrez-20. The reason? Sensorials. I found that 940 is better for creams and Ultrez is great for gels.
    Preservatives: We have been using Spectrastat at 0.7% for years and never had a failure even with difficult to preserve items. But we do use hurdle technique too.
    Cosmetic Brand Creation. Concept to name to IMPI search to logo and brand registration. In-house graphic design inc. Pantone specs. Cosmetic label and box design & graphics.
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