Understanding Emulsions - when to use O/W vs W/O

I've read some articles about emulsions and I understand that there are two types of emulsions. O/W (oil suspended in water) vs W/O (water suspended in oil).

Is there a general rule for when we should use an emulsifier that is O/W over one that is W/O? My initial assumption would be that you'd want to suspend the component that composes a smaller portion of the recipe in the component that is the major portion of the recipe. That is, if most of your ingredient is water, you should suspend oil-in-water.

However, I was reading the ingredients list for Suavecito Pomade and it looks like the majority of the ingredients are oil with a little bit of water (Aqua being listed after several waxes/oils). But, it is using Cetereath-20 which is an oil-in-water emulsifier so my hypothesis is incorrect.

Can someone explain to me when I would want to use W/O vs O/W emulsifiers (or provide a link to a good article)?


Comments

  • ngarayeva001ngarayeva001 Member
    edited February 10
    You can create W/O emulsion with water phase less than 15% and O/W emulsion with an oil phase more than 85%. It has nothing to do with the amount of oil and water. You chose the type of emulsion based on the product. Majority of foundations and some sunscreens are formulated as W/O. Some high-end face moisturisers also formulated as high internal phase W/O. W/O are hydrophobic, so when you want to get this quality, you chose W/O. I haven't seen hair products formulated as W/O, my attempt to create one wasn't particularly successful. The pomade above is O/W.
  • Your assumption isn't entirely wrong. In my most technical scientific explanation: science is hard and there is so much at play even in  simple formulas. I attached some references I like.

    Check out HIPE (High internal phase emulsions) too.

    Also keep in mind the end goal is to create a stable product. Pomades are thick and you might be able to get away with an unconventional emulsifier choice and have a product stable enough to sell.

    From the ICI attachment the author says
     In other words, you use a "water-soluble" emulsifier when you want your final product to exhibit aqueous characteristics, i.e. to dilute readily with water"

    Maybe this emulsifier is helpful in washing that pomade off at the end of the day

  • Bill_TogeBill_Toge Member, Professional Chemist
    also, if the ingredients list is accurate, the product is missing a low-HLB emulsifier, and going by its appearance, it appears to be a highly concentrated surfactant gel rather than a conventional emulsion
    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
  • @EVchem Thanks for the pdfs! I'm going to read them soon :)

    @Bill_Toge I'll have to google a few of those terms since I'm pretty new to this 
  • Bill_TogeBill_Toge Member, Professional Chemist
    for what it's worth, hot-fill styling products are some of the most complicated products on the market in terms of formulation
    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
  • Thanks, I'm on the struggle bus choosing to do a water/oil + clay pomade as my first formulation so that makes me feel a bit better :)
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