How to define a water in oil emulsion?

Hey everyone! I’m not a chemist (my bad!), so sorry for these silly questions, but I would really appreciate your help! I’m also looking for an experienced chemist for paid consultations, so please send me a message if you’re interested.

So the questions are:

1. Is it possible to realize what kind of an emulsion it is looking at the skin care formula? I mean if there are specific emulsifiers or combination of ingredients that work only for w/o emulsions?

2. Another question is - is it still true that w/o still tend to contain less of water (27 to 75%) as opposed to o/w (52 to 80%) or recently the ratio has developed to be the same 60-80%?

Thank you very much!

Comments

  • Is it possible to realize what kind of an emulsion it is looking at the skin care formula? I mean if there are specific emulsifiers or combination of ingredients that work only for w/o emulsions?

    While i'm not a chemist, normally i look at the emulsifier used and look into what kind they are. That's how i normally determine that they would be. Looking at the related rheology modifiers like the water based or oil based thickeners would also give you a clue since it can be restrictive for w/o emulsions. 

     Another question is - is it still true that w/o still tend to contain less of water (27 to 75%) as opposed to o/w (52 to 80%) or recently the ratio has developed to be the same 60-80%?

    I believe it would depend on the emulsifier. For example, based on the specs sheet of ABIL® EM 90 (Cetyl PEG/PPG-10/1 Dimethicone), the optimal oil phase is about 20% to 35% depending on whether lotion or cream. 

  • Bill_TogeBill_Toge Member, Professional Chemist
    edited January 20
    if the product contains a high-HLB emulsifier, you can be sure it's O/W; it's not physically possible to form W/O emulsions with high-HLB emulsifiers present
    having said that, there are numerous products with incomplete or misleading ingredients lists, so the only way to be sure is by physically examining the product
    the relative ratio of oil to water is irrelevant - the nature of the emulsion is determined entirely by the nature of its emulsifiers, as there's no way for the system to 'know' how much oil or water is present
    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
  • Bill_Toge said:
    the relative ratio of oil to water is irrelevant - the nature of the emulsion is determined entirely by the nature of its emulsifiers, as there's no way for the system to 'know' how much oil or water is present
    Thank you for the answer! From your experience, what is the water content in w/o emulsions you come across most often?
  • One of the main give aways is salt. If you see sodium chloride, magnesium sulfate or zinc sulfate it’s most probably w/o. Salt is crucial for w/o stability. 
  • MicroformulationMicroformulation Member, Professional Chemist
    The percentage of water really has no impact upon determining if it is O/W or W/O. As @Bill_Toge quite correctly pointed out, you need to look at the emulsification system.

    markfuller@microformulation.com Microformulation.com 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.
  • The percentage of water really has no impact upon determining if it is O/W or W/O. As @Bill_Toge quite correctly pointed out, you need to look at the emulsification system.

    I totally get it! The ratio question is not about defining the type of emulsion. I’m just trying to understand whether if you take all w/o emulsions and compare them to all o/w, overall they’ll contain less water. Because I keep getting contradictory opinions: some say w/o statistically have less water, others say that due to recently developed efficient emusifiers the amount of water is the same.
  • It goes back to the emulsification system. 

    So are you asking if statistically if there are more W/O emulsifiers that enables formulation with a smaller water phase compared to oil phase, verse larger water phase compared to oil phase? 

    Because not forgetting, even if there are more emulsifiers that of either one, it's up to a formulator to choose which one they want to use and it can skewed towards one end because of certain reasons, so there are 2 factors to your thought.  
  • jemolian said:
    It goes back to the emulsification system. 

    So are you asking if statistically if there are more W/O emulsifiers that enables formulation with a smaller water phase compared to oil phase, verse larger water phase compared to oil phase? 

    Because not forgetting, even if there are more emulsifiers that of either one, it's up to a formulator to choose which one they want to use and it can skewed towards one end because of certain reasons, so there are 2 factors to your thought.  
    No no, I’m not asking about that. I just want to find out if it’s true that w/o emulsions usually contain less water than o/w emulsions. I’m not trying to define the type by the water content, I just want to get the picture of the difference of water content in these two types of emulsions. Say if you take 100 random o/w emulsions and compare to 100 random w/o, what will be the difference in average water content? Or there won’t be?
  • As @Bill_Toge and @Microformulation mentioned ratio of oil to water is irrelevant.
    Somehow you can estimate water content in o/w emulsion, but you will see various oil to water ratios in w/o.
    It is depended on how the formulator approach the formulation. I believe this is one of the reasons why w/o cost more than o/w per formulation. I myself as a non-professional can't simply do a knock off foundation formulae with out a guide sheet from suppliers.
  • PerryPerry Administrator, Professional Chemist
    A trick you can use to determine if a finished product is o/w or w/o is to take a small sample and drop it in some water. If the drop of product starts to spread out and dilute then it's o/w.  If it remains in a little ball with minimal interaction with the water, it's w/o.
  • Perry said:
    A trick you can use to determine if a finished product is o/w or w/o is to take a small sample and drop it in some water. If the drop of product starts to spread out and dilute then it's o/w.  If it remains in a little ball with minimal interaction with the water, it's w/o.
    Wish I could do that! But I only have a bunch of ingredients lists, not the physical products.
  • https://incidecoder.com/products/sisley-black-rose-skin-infusion-cream

    https://incidecoder.com/products/khiels-creamy-eye-treatment-with-avocado

    https://incidecoder.com/products/bioderma-abcderm-peri-oral

    Several commercial W/O as an example. All have certain things in common: W/O emulsifier high up in the LOI, oil phase stabilisers and lack of common water phase stabilizers that you would expect to see otherwise (like xanthan or carbomer), presence of a salt somewhere around 1% line. If not a sunscreen and properly formulated, I wouldn’t expect seeing high polarity esters high up in the ingredients list.

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