Concentration of Emulsifier?

There seems to be very little information about how much emulsifier to use in an oil-in-water emulsion.  The concentration of emulsifier in any formula would have to have some direct relationship to the amount of Lipids that need to be emulsified in the formula.  For example if you're Lipid phase is 20% of the total formula, then would you use 1%, 2%, 3% or 4% to have an emulsion that is both stable and cosmetically gentle but effective.  I only found one laboratory/manufacture of cosmetic supply ingredients that mentioned an "optimal" amount would be 10 percent matching the Lipids phase - for example if you have 30% lipid phase, then they recommend using 3% emulsifier(s), which should be a blend of high-HLB and low-HLB emulsifiers.  I understand that if you increase the amount of emulsifiers higher than is necessary you are decreasing the molecular size, but also potentially creating something that could irritate the skin because it could be too "soapy" or have cleansing qualities.

Anyone have information and/or experience about a good protocol for matching the concentration of emulsifier to the percentage of lipid phase in the formula.

Comments

  • johnbjohnb Member, Professional Chemist
    Very rare is the cosmetic emulsion that comprises only three ingredients (oil, water and emulsifier). Additions such as solvents, emollients, electrolytes, different types of oily material and many others will profoundly influence the formation and stability of an emulsion product. This is where the knowledge and experience of a cosmetic chemist or formulator is invaluable. If cosmetic formulation were as simplistic as you seem to want or expect, most members here and lots of others would be unemployed.

    The singular example you gave:
    I only found one laboratory/manufacture of cosmetic supply ingredients that mentioned an "optimal" amount would be 10 percent matching the Lipids phase - for example if you have 30% lipid phase, then they recommend using 3% emulsifier(s), which should be a blend of high-HLB and low-HLB emulsifiers.

    shows little knowledge of the real world and I suggest it should be ignored - similarly with the next sentence in your post.


  • Bill_TogeBill_Toge Member, Professional Chemist
    edited April 2017
    it also depends on what kind of emulsifiers you're using, the desired rheology and viscosity of the finished product, and how the product's viscosity varies with temperature - in short, there is no simple one-size-fits-all solution!

    from my experience, making the appropriate choice of emulsifier is more important than the level; the emulsifier(s) need to be chemically compatible with both the water and oil phase, and have the correct HLB for the oil phase

    if emulsions show inherent instability that's independent of temperature, it's usually because the emulsifying system has failed to meet one or both of these criteria
    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
  • MarkBroussardMarkBroussard Member, Professional Chemist
    @doctorbrenda

    There is no protocol as such matching the % emulsifier as a % of the oil phase.

    Each manufacturer will have a recommended % of their particular emulsifier to use and stabilitzers/co-emulsifiers to get the best result.

    For instance, if your oil phase is 17% and you're using Olivem 1000 (HLB 9) you'll want to use 6% to 8% Olivem, 0.2% Xanthan Gum and 1% to 2% Glyceryl Stearate.  The co-emulsifier that you use will also be a function of the required HLB of your oil phase.  But, using the same exact oil phase, if your using a different emulsification system, say Montanov 68 and Montanov 82, you might use 2% to 3% of each.

    So, the question you are posing does not have an answer ... it all depends on the HLB of the oil phase and the emulsifiers that you are using.

    BTW:  That manufacturer/laboratory that told you the 10% rule regarding emulsifiers/oil phase ratio ... I'd think twice about the advice they are giving you.
    Chemist/Microbiologist formulating in the Organic & Naturals & Clean Beauty arena under ECOCert/Natural Products Assn/Whole Foods/National Organic Program/Clean At Sephora/Credo Clean guidelines focused skincare & haircare products. 

    See website for details www.desertinbloomcosmeticslab.com
  • I can see that what I really need to do is spend more time writing a longer explanation before asking a question.  I think everything was posted here is well understood by formulators.  I did not say the formulas in question only contained "3 ingredients (oil, water, emulsifier)".  The reason I kept referring to it as the "Lipid" phase is because anything there are many different substances that fall into that general category, including but not limited to wax esters, siloxanes, fatty acids, phytosterols, triglycerides, monoglycerides, all vegetable oils and butters, fatty alcohol waxes, and of course there are solvents and humectants as well, but since they are water soluble, it is not considered a lipid that needs to be emulsified in the "Lipid" phase.  Emollients are usually substances that also need to be emulsified with water, and therefore fall into the category of the lipid phase.  I don't think most people are calling it the "oil" phase anymore, at least not when they understand that there are so many other substances that need to emulsified in order to mix with water.  I cannot believe I need to explain this in order to correct a misunderstanding.

    Anyway, moving on, I think it is also well understood that manufacturers have a general guideline as to the concentration (like 2% to 6% of substance A, or 3% to 10% of substance B, etc.).... but whether you use the minimum or maximum that is "recommended", which is just a suggestion not a requirement, ALL DEPENDS on HOW MUCH and WHAT TYPE of substances that you are emulsifying.

    If you use too little, no matter great you think the rest of your formulation was calculated (including the required HLB), it will most definitely fail.  I have NEVER had a problem with a failed emulsion, probably because I studied up on this stuff for three years before ever running a single experiment, so I had a good enough base of knowledge.

    So the reason I did not write ANYTHING about calculating the required HLB for any formula is because I thought that would be naturally presumed.  So with my question, any experimental formula has has ALREADY BEEN CALCULATED TO DETERMINE THE REQUIRED HLB.  I seriously thought everyone would know that you should always calculate the required HLB of your formula, so that you can determine what type of emulsifier blends to use.

    Thank you so much!  I appreciate that feedback because it has taught me what I need to do before posting any discussion piece.


  • MarkBroussardMarkBroussard Member, Professional Chemist
    edited April 2017
    LOL! ... if you had already calculated the HLB of your "Lipid" phase ( sorry, real "pros" call it Oil, not Lipid phase ) then you would know that the HLB calculation yields what ratio of each emulsifier to use and with the manufacturer use guidelines you would have a range of recommended use of each emulsifier.

    So, if you know all of all that in advance, then you would know that your original question regarding a general rule for the percentage of emulsifier to use doesn't have an answer.

    Science is the process of experimentation ... there's a big difference between reading about it and doing it.
    Chemist/Microbiologist formulating in the Organic & Naturals & Clean Beauty arena under ECOCert/Natural Products Assn/Whole Foods/National Organic Program/Clean At Sephora/Credo Clean guidelines focused skincare & haircare products. 

    See website for details www.desertinbloomcosmeticslab.com
  • PerryPerry Administrator, Professional Chemist
    @doctorbrenda - I think you have misunderstood what some of the responders were saying. Text is not always the best way to explain things.

    For example, I didn't read @johnb as suggesting your system had 3 ingredients. I took it to mean that your question would only have a simple answer if your system contained only 3 ingredients. But clearly your system contains more than that so there isn't a simple formula / answer that would apply.

    My answer to your original question is this, there is no simple solution to matching emulsifier concentration to oil (lipid) phase. All systems are different and the only way you can figure out how much emulsifier you should use is to conduct an experiment.  So, here's a reasonable protocol.

    1.  Start with some ratio of emulsifier to oil phase. This is a guess based on experience, supplier information and anything else. 1:10, 1:4, 1:5, 50:50. Whatever you want.

    2.  Make the batch and see how it comes out.  Did it make an emulsion? Did the system look and feel they way you wanted? 

    3.  If it doesn't look & feel the way you want, try a different ratio. Increase or decrease the emulsifier, increase or decrease the level of oil phase & remake your batches.

    4.  If it looks good, then put up a stability test and see if it remains stable. If it's stable after 3 months, congratulations your formula is stable.

    5.  Repeat this process until you've got your answer.

    Note: if you change the level of anything else in your system or add a new ingredient, you will likely have to adjust your emulsifier / oil phase ratio.

    Of course, this protocol also assumes you are using the same level of mixing and heating. Those factors can influence how much emulsifier you need too.

    The bottom line is that the answer to your question is complicated.

  • johnbjohnb Member, Professional Chemist
    Of course the ultimate arbiter in all of this is the consumer/user of your precious, stable emulsion. No matter what physical or chemical attributes it may have, if the user doesn't like it you have completely wasted your time.
  • MarkBroussardMarkBroussard Member, Professional Chemist
    @Perry:

    LOL! ... Get with the program man ... in your reply you continuously used the term "Oil Phase" ... it's "Lipid Phase" ... Now I'm off to make a batch of Lipid/Water emulsion using my standard 10% emulsifier to Lipid Phase ratio.  Works like magic, every time!
    Chemist/Microbiologist formulating in the Organic & Naturals & Clean Beauty arena under ECOCert/Natural Products Assn/Whole Foods/National Organic Program/Clean At Sephora/Credo Clean guidelines focused skincare & haircare products. 

    See website for details www.desertinbloomcosmeticslab.com
  • Wow!  Okay people, I think this is what happens far too often with text/internet communication.... to much opportunity for misinterpretation.

    Perry, thank you for your mature, professional, respectful response.  I'll just ignore some of the other more dramatic, sarcastic responses.

    What I really should have done is just posted 3 formulas that are almost identical, with only differences in emulsifier blends, concentration levels, etc... for the sole PURPOSE of discussing quality and textural differences, and how they interact with each other, etc.  That's where I was really hoping to go with this (not where it ended up going).  I guess this is not the place, nor the people with which, to have those conversations.

    With that said, I did get some really good answers from two different cosmetic pharmacists - so my question was valid, but the answers are more complicated than what could be reasonably discussed in this forum.  They gave me some very different information (in fact, in complete contrast) from what I've read on this website, but I don't want to offend anyone by posting it, because I'm sure some will find that type of expert feedback to be "invalid" or something that should be "dismissed" or "ignored", etc., and that's not going to lead to a forum of progressive learning, sharing experiences, and co-education.

    And no worries John, everyone likes the formulas I've created... it's just me that wants to fine-tune them, and always trying to improve things.... being perfectionistic can be more work than it's worth sometimes.


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