One question I’m often asked as a cosmetic formulator and as a tutor is: “What is your favourite emulsifier?”. I should confess that I have no response to it. It is exactly the same as choosing your favourite “preservative” in the case of a cosmetic formulation. There is no one single emulsifier that will be suitable for every situation.
The response mainly depends on your system, your concept, other ingredients in the product and so many other factors. There might be a “favourite or best emulsifier” for a certain purpose but it doesn’t mean you can cover all your requirements with a single emulsifier.
Since I’m going to review a few emulsifiers for you during the upcoming weeks and months, I decided to write this post as an introduction. I’m going to recommend some essential questions which you can ask your supplier, or you can try to find the answers in a data sheet. In some cases you may even need to find the answer by “trial & horror” with experiments before you make up your mind to choose a certain emulsifier in a certain system.
So here are my 17 points you need to consider before choosing an emulsifier:
1. Natural vs. Synthetic
“Natural” has 50 shades and since there is no unique and universally accepted definition for “natural” in cosmetics, this question will always cause us a headache and sometimes even emotional (and not rational) discussions and debates. Keep in mind that even lecithin which is probably one of the most “natural” emulsifiers, needs to be extracted, separated, processed out of plant oils and fats until it becomes the lecithin that you know.
It is very unrealistic to believe that an olive oil based natural emulsifier such as “cetearyl olivate” comes directly from the olive fruit or olive oil without being processed or having undergone some chemical reactions.
However, there are some emulsifiers that are, even to my chemist’s taste, synthetic and have no place in a natural & organic formulation. The most prominent synthetic emulsifiers are derivatives of PEG (Polyethylene Glycol) or PPG (Polypropylene Glycol). This includes the whole polysorbate and Tween range and other emulsifiers such as dilaureth-7 citrate.
2. Certified or not certified, that is the question
Your supplier should be able to inform you whether your emulsifier is organically certified (and how it is certified) or not. Not all “natural” emulsifiers are going to be certified. This is mainly because of the high costs of certification, which in the end affect what the consumer is going to pay. It depends on your market, claims and concepts whether you confine yourself to a certified emulsifier or not. If you are going to have your finished product certified, then you need to consider this factor.
3. Global acceptance
Depending on your target markets, you will sometimes need to consider the global status of the emulsifier. Being vegan, halal or kosher are for instance other criteria which you need to consider for specific markets.
4. Is it Palm-oil free?
If you’re concerned about your products being palm oil-free or you insist upon using fair and sustainable palm oil, then have an exact look on the datasheet and ask your supplier about the origin of the ingredients.
Keep in mind that the emulsifier doesn’t necessarily need to carry the name “palm” to be palm-derived. Many plant-derived ingredients such as cetyl alcohol, cetearyl alcohol (and their derivatives) are derived from palm oil as an affordable starting material (unless your supplier specifically has used other plant oils to derive these ingredients).
There are even different shades of sustainability. Some companies only pay a certain amount per year to get a “sustainable” stamp without really working with sustainable palm.
HLB stands for “Hydrophilic Lipophilic Balance”. This system was developed for PEG-based ingredients and it really was a great help. For modern, PEG-free emulsifiers and especially in natural & organic cosmetics where you most often emulsify plant oils (i.e. there are no paraffins or silicone oils that need to be emulsified), this old system is not really essential.
Most data sheets do not even mention the HLB for modern emulsifiers. If however the HLB is mentioned, you want to know very roughly if the HLB of a certain emulsifier is around 4 (W/O emulsifier) or around 11 (O/W emulsifier). If there is no mention of the HLB, the data sheet should at least mention the type of the emulsifier: W/O (water-in-oil) or O/W (oil-in-water).
6. Optimum oil phase concentrations
Most emulsifiers work best in a certain range of oil phase, where the amount of oil used in the products effects the performance of the emulsifier.
Some emulsifiers will work best in a low oil range (3-10%), whereas some work best in medium oil phase range (15-25%) and yet others some can emulsify high oil concentrations (this generally applies to W/O emulsions). Depending on the concentration of the oil phase (or water phase), you should try to find the most suitable emulsifier for that system. If a certain emulsifier works in your emulsion with 5% oil, it will very probably not be the best choice for another emulsion with 40% oil phase.
7. Viscosity range
Sometimes you want to make a thick, rich night cream, sometime a low viscosity sprayable light emulsion. Although the viscosity of an emulsion could be adjusted by applying gums and other viscosity modifiers, you shall check the specification of the emulsifier whether it is suitable for your desired viscosity range. This would be specially very important in case of low viscosity emulsions. Not all emulsifiers will work in those systems.
8. Need of an stabilizer/ a co-emulsifier
Some emulsifiers may need a co-emulsifier or an stabilizer in certain systems – for example, when you’re working with alcohol or trying to achieve a certain viscosity. You need to consider your desired viscosity as you plan your system and consider the costs and logistical requirements of a certain formulation. More importantly, if a certain emulsifier works only with a synthetic stabilizer such as carbomer, then it would not be a suitable choice for your organic and natural formulation.
9. Electrical charge
Most modern emulsifiers are neutral esters, however, you may find some emulsifiers with an ionic character such as Glyceryl Oleate Citrate, which has an anionic character. These ionic emulsifiers might not be compatible with other ionic ingredients. In the case of Glyceryl Oleate Citrate for example, this emulsifer isn’t compatible with cationic surfactants and cationic guar applied in hair conditioners.
10. Best working pH range
Each emulsifier has a best working (and stability) pH range. Deviation from that pH caused instability, changes in viscosity, texture or appearance. You need to particularly think about your product’s pH as you plan for your preservative system. If you’re going to use a weak acidic preservative system with the highest efficacy at a pH lower than 4.5 and your emulsifier works best at a pH of 6-7, the you should either change the preservative or the emulsifier.
For hair dyes, depilatory products or chemical peels (Alpha-Hydroxy Acids) your product would have a pH much higher or lower than the neutral range of conventional emulsions. These products might need special emulsifiers or at least specific stabilizers and co-emulsifiers. Some ionic emulsifiers are so sensitive to pH changes that you may need to apply a buffering system to keep the system stable during the determined shelf-life.
11. Electrolyte tolerance
Electrolyte tolerance can indeed affect many emulsifiers. In most cases, you won’t apply electrolytes in your emulsions, but in some specific cases such as anti-perspirants with high Aluminium salt concentration or some cleansing emulsions with ionic surfactants, or even applying clays, you incorporate electrolytes into system.
Ask your supplier about the electrolyte tolerance of the emulsifier if it is not already mentioned in the data sheet. You should also consider if your preservative (or the preservative in some of your other ingredients such as hydrosols and plant extracts) contains electrolytes.
12. Alcohol tolerance
Much like electrolytes, alcohol can destabilize many emulsions. Ask your supplier about the alcohol tolerance of your product if you are going to apply alcohol in your emulsions.
13. Oil phase character
An oil phase is not always an oil phase. Making natural cosmetics, you’ll probably work most often with plant oils, waxes and butters but in some cases you may want to use fractionated oils, fatty alcohols or monoesters instead off fats and oils (triglycerides). Make sure that the emulsifier you choose is suitable for emulsifying your desired ingredients.
14. Cold vs. hot process
Most common emulsifiers are pellets, flakes or powders that can be melted with the oil phase (or sometimes with the water phase). This will sometimes be a disadvantage as you work with sensitive ingredients which may be heat sensitive.
There are however a few (liquid) emulsifiers that allow you to use a cold blending technique. This approach will save you time and energy when working with cold process emulsifiers.
There is however no use in searching for a cold process emulsifier if you know that you want to emulsify mango butter or coconut oil or other ingredients that are solid at room temperature and should be melted. On the other hand if you’re going to prepare an emulsion based on borage oil or grape seed oil, it would be reasonable to search for a cold process emulsifier.
15. Manufacturing procedure
Unfortunately online blogs and the DIY community have perpetrated the myth that to make a water-in-oil (W/O) emulsion you need to add the water phase to the oil phase, and when making an oil-in-water (O/W) emulsion you need to add the oil phase to the water phase.
Although this may be correct in most cases, you need to be aware that there are many exceptions. Follow the manufacturer’s instructions but don’t be frightened to test it the other way around as it might really work in your system.
16. Shear tolerance
As an organic skincare entrepreneur, the shear tolerance of your emulsifier might be one of the most important practical parts to consider, depending on the type of equipment you’re using – particularly if you’re working with stick blenders, hand mixers, kitchen aids and whisks.
Some emulsifiers do need a homogenizer and high shear, some do not like high shear at all and would be destabilized if you used a homogenizer. This aspect is seldom mentioned in the technical data sheet. Ask your supplier for manufacturing guidelines or some sample formulations.
17. Application dosage
As a very general rule of thumb, the emulsifier is applied at about 20% of the oil phase. There are some emulsifiers that might work best at lower concentrations and there are some that should be applied at higher concentrations (especially when working with low oil concentrations). This should be considered in your overall planning and calculations.
You may reduce the concentration of the emulsifier by applying some co-emulsifiers or stabilizing agents. But when you do this, make sure you consider the overall cost of your ingredient as it doesn’t make sense to reduce the concentration of a given emulsifier to 0.2% by applying 0.5% of a gum when the emulsifier costs $50/kg and the gum $150/kg.
Questions to ask your supplier
We have a thriving online classroom for our Students & Graduates and one topic that frequently comes up there is – what should I ask my suppliers when trying to choose the right ingredients?
In order to help you determine which emulsifier to choose, we’ve prepared this FREE simple fact sheet for you. Download it and use it to review the technical data sheets you receive from your supplier, along with any other information you hold about your favourite emulsifier.
Depending on the ingredients, equipment and techniques you’re working with, some of the questions in this fact sheet may not be relevant. Focus on those questions which are relevant to you and your system. For instance, if you never apply alcohol in your products, and there isn’t any alcohol in any of your raw materials, then alcohol tolerance will obviously not be of relevance.
Feel free to add any other questions which are important to you and your specific requirements and then attach this table to your emulsifier’s data sheet or in a separate file when you can quickly and easily review it when you need it.
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Dr. Elham Eghbali was Formula Botanica’s Cosmetic Chemist between 2014 and 2018. She has over 20 years’ industry experience and is based in Bavaria, Germany. To read more about Formula Botanica’s team, visit our staff page.