As a cosmetic chemist you will undoubtedly be asked to make products that require you to combine materials that aren’t easily compatible. Fortunately, there is a system that can help you get started.
Cosmetic Emulsions
Emulsions are one of the most common forms of cosmetic products. You find them in skin lotions, make-up, and even hair products. By definition an emulsion is a dispersion of two or more immiscible materials, where one phase, also know as the internal phase, is dispersed in the continuous or external phase. Cosmetic emulsions are classified as oil in water (O/W), water in oil (W/O) and water in silicone (W/Si). Multiple emulsions such as oil in water in oil (W/O/W) are also possible. Oil in water emulsions are the most common due to preferable cost and light skin feel.
In order to create an oil in water emulsion (one that remains stable for a long enough time), work must be done to overcome the interfacial tension between the two phases. This can be achieved by mixing; however mixing even at very high rates is not enough to provide long term stability. An emulsifier or combination of emulsifiers is needed to stabilize droplets of the dispersed phase. For example, simple oil in vinegar salad dressings will separate rapidly without the use of an emulsifier like mustard.
Using Surfactants
In this industry, we use surfactants to create emulsions. Surfactants are molecules that have a hydrophobic (oil soluble) and an effective hydrophilic (water soluble) portion. They act as emulsifiers by significantly lowering the interfacial tension and decreasing the coalescence of dispersed droplets.
HLB Formulating
Figuring out what surfactant to use for any specific formula will be a challenge you face as a cosmetic chemist. There is a great deal of research on surfactants and their behavior. But studying the thermodynamic equations and phase diagrams associated with surfactants can be a daunting task, not to mention the number of surfactants available to the formulator is vast. Luckily for us, William C. Griffin developed a way to streamline the selection of surfactants by utilizing the ratio of the hydrophobic to the hydrophilic portion of the molecule. This method is referred to as the HLB (Hydrophile Lipophile Balance) method. Griffin first presented this method at meeting of the Chicago Chapter of the Society of Cosmetic Chemists in 1949 and it is still widely used today. He published the method shortly there after.1 (A bit of trivia for you, the Chicago Chapter was the first chapter formed in Society of Cosmetic Chemists)
The HLB method applies to nonionic (uncharged) surfactants but attempts have been made to broaden the concepts to other surfactant types including silicone surfactants. And using the HLB system to create emulsions is quite simple. All you have to do is calculate the HLB number of your surfactant, then the Required HLB for the oil phase and match the two numbers.
Determining the HLB of a surfactant
A typical nonionic emulsifier (e.g. Laureth-4) contains an ethylene oxide groups or polyhydric alcohol hydrophilic portions with a fatty alcohol hydrophobic portion. The HLB for a nonionic surfactant can be calculated as follows:
HLB = Weight % Hydrophile/5
Example 1: HLB calculation for Laureth-4
Molecular weight of ethoxylate portion = 176
Molecular weight of lauryl alcohol = 186
Wt. % Hydrophile = (176/(176+186)) x 100 = 48.6%
HLB = 48.6/5 = 9.7
Based on the calculation, surfactants with high HLB values will be more water soluble and those with low HLB values are more oil soluble. Division by 5 just allows for a compact, easy to use scale. The calculation is simple, but you won’t usually have to figure it out since most surfactant HLB values are readily available through literature references and surfactant suppliers.
Calculating HLB of oil phase
Each lipophilic ingredient in the oil phase has its own required HLB. These required HLB values are determined experimentally, however a method utilizing solubility parameters has been proposed by Vaughan and Rice.2 Required HLB values for some common oil phase ingredients are available to the formulator in literature. The Req’d HLB values are approximate and can vary by about ± 1 unit. It is also important to keep in mind that cosmetic emulsions often have complex oil phases with several components. The required HLB of an oil phase mixture can be calculated by first calculating the percent of the oil phase each ingredient contributes. This percentage is then multiplied by the required HLB for each of those ingredients and the results are summed.
Example 2: Calculation of required HLB for an oil phase mixture
The oil phase is 10% of the total formulation and consists of:
4% Shea butter, 40% of the oil phase. Req’d HLB of 8.
3% Jojoba oil, 30% of the oil phase. Req’d HLB of 6.5.
3% Sunflower seed oil, 30% of the oil phase. Req’d HLB of 7.
Total required HLB:
Shea butter contribution 0.4 x 8 = 3.20
Jojoba oil contribution 0.3 x 6.5 = 1.95
Sunflower oil contribution 0.3 x 7 = 2.10
Total Req’d HLB = 7.25
You can now select emulsifiers to match the required HLB of the oil phase and create an emulsion. A blend of high and low HLB surfactants is often used to achieve the desired value in part because of demonstrated effectiveness and efficiencies in packing at the interface. The HLB for the surfactant blend is calculated in same manner as the required HLB for a blend.
Example 3: Calculation of HLB for a surfactant mixture
The surfactant mixture is a 70/30 blend of Steareth-2 and Steareth-21.
Total HLB:
Steareth-2 contribution 0.7 x 4.9 = 3.43
Steareth-21 contribution 0.3x 15.5 = 4.65
Total HLB = 8.08
In order to match the HLB of a particular oil phase, it is easiest to set up a spreadsheet with the calculation and vary the percentages of each emulsifier in increments of 5% to find the right ratio.
Limitations of HLB
Although a very useful tool, the HLB system does have some limitations. For example additional water phase ingredients are not considered but still may impact the stability. The method also does not provide information as to how much surfactant is needed, but 2 to 4% surfactant is a good starting point to begin further optimization for stability. So it is important to keep in mind that the HLB system is not absolute in prediction of your formulations behavior, but a very good starting point for achieving emulsification.
References
1. Griffin WC; Calculation of HLB Values of Non-Ionic Surfactants, Journal of the Society of Cosmetic Chemists; 1954. Vol. 5, pp 249-235
2. Vaughan, C.D. Rice, Dennis A.; Predicting O/W Emulsion Stability by the “Required HLB Equation”; Journal of Dispersion Science and Technology; 1990. Vol. 11 (1), pp 83 – 91.
{ 82 comments… read them below or add one }
Dear,
I have done several trial & error but finally couldn’t get clear/transparent emulsion.I donno where the problem is?Required HLB for oils & Hlb of my surfactant all is maintain somehow in my little knowledge.But still solution become milky/to cloudy.I am trying to mix some of my essential oil blend like(Tea-tree,thyme, eucalyptus,cardamom, cinnamon,spearmint)to purified water to get a clear solution without using any alcohol. But always my solution become milky even oil & water mixed properly.Could anyone suggest some way to come out form the error?
I would suggest you post this question to the forum as you might receive more responses. http://chemistscorner.com/cosmeticsciencetalk
Could you tell me how to calculate the required HLB for menthol and for peppermint and spearmint oils.
Thanks,
You can search for published values or determine experimentally. To determine experimentally you would prepare emulsions with surfactant blends from high to low HLB values and the one that is most stable would assigned as the required HLB.
dear kelly
thanks for your guidance .i do that……
any one can help to me?
dear kelly:
can you answer to me?
my problem is about making a stable emulsion w/o
oil is vaseline and system HLBis about 7.35
thanks for your guidance .
hasni,
You will have to determine determine the right emulsifier system experimentally.
i want to make a stable emulsion from water(that some salts are solved in it)and vaseline(petroleum jelly)
which kind of emulsifier is suitable for it?i use of GMS but it was separated after some minute,however is it posible that after solidification of cream and remelting it i have a permanent emulsion?
So… if you calculate the required HLB of an Oil Phase and the result is around 3-8, the emulsion will be an w/o.
And if you calculate the required HLB of an oil Phase and the resulst i 9 or above, the emulsion will be an o/w.
Is this true???
What type of emulsifier can replace PGPR in emulsion that is added to the oil at 0.1%
That’s not enough information about the formula to give you a credible answer.
Water soluble material is disolved in 24% water. 10% PGPR is added to the oil phase. this emulsion at 0.1% will be added to the oil.
Try alternate low HLB emulsifiers. You can find HLB values for a range of surfactants just by searching online.
I have some questions to grit or small particulate that will go away upon a little rubbing in the final product. Would this be a for of flake that is a fall out in the emulsion or is this a solid particle film that could be forming in a formula?
We are currently using polyglyceryl-3-diisostearate as well as glycerin.
Oils: Mineral Oil, Cream Petro, Synthetic Beeswax which accounts for about 50% and then water is approximately 30%. Any help/insight would be greatly appreciated!
Dear
I want to make an emulsion of Menthol and eucalyptus oil in water. Please suggest me some solution.
Thanks
Hi
I would like to make a sprayable sunflower oil emulsion. What emuslifier should I use and in what proportion? Thanks
Dear Kelly,
Could you kindly help me in how to make a stable silicon emulsion and a stearic acid emulsion using a 2 stage homogenizer?
Thanks in advance and congratulations for your article.
Charlie C.
How to get an o/w emulsion?
If oil phase HLB required is 7.2, and you ad a high HLB emulsifier (15.5) and and low HLB emulsifier (4.4) in a ratio that is 7.2, what type of emulsion do you get? I thought unless HLB was > 10 (or there abouts) that you’d get a w/o
You are correct, lower HLB surfactants (4-6) are W/O emulsifiers but other formulation factors like the size of the oil phase can effect formula type. You can simply test what type you have by trying to dilute the final product with water. A W/O does not dilute while a O/W would/
I need to a sprayable oil-in-water. My oil, soy bean oil, has a HLB of 7. I have tried soy lecithin (HLB =7) and still had major separation. Any ideas on any other emulsifiers I can use?
Thanks1
Hi Cindy,
Keep in mind that it best to use a high HLB and low HLB in combination to match the required HLB. Also the level of emulsifier may need to be inceased.
I find it so encouraging that I’m not the only human out there over the age of 20 who doesn’t know any of this!
Time to learn *about all of it*.
Hi there, i have aproblem in mixing jojoba oil & glycerin using Tween 80 at 8% & span 8o at12 % the emulsion separate , did Iuse the right emulsifier or the % is wrong please repply & many thanks
While it looks like your HLB is balanced, that’s quite a lot of emulsifier. Start with 2 to 4%. Also, is glycerin the only component of your external phase? If so the HLB method may not be a good predictor for stability.
Hi all
I want to ask if there is any negative effect of using too much emulsifier in a water in oil cream( except for paying more money)
I mean can excess emulsifiers cause instability???
One of my experiments has shown that using 3% of sorbitan sesquioleate is less stable than using 2% !!!!
Can any one answer or guide me?
Second, I want to ask about cooling phase, should it be done in very cold water bath and done quickly or it is better to cool the cream slowly !!!
Please help me ?
Thanks in advance
George
Hi all,
i want to create different conditions and substrates for biosurfactant production by a Bacillus subtilis strain. How do i determine the HLB value of the biosurfactants that will be produced?
You would need to know the structure of your surfactant, and keep in mind, HLB applies to ethoxylated nonionic surfactants. I’m not familiar with biosurfactant structures, so I don’t know whether the HLB method applies.
You can make some VERY approximate estimates by observing solubility in water as follows:
Dispersability HLB Range
None in water 1-4
Poor 3-6
Milky w/ vigorous agitation 6-8
Stable milky dispersion 8-10
Translucent 10-13
Clear solution 13+
(copied without permission from ICI publication “The HLB System”)
Whoa! You have an old ICI publication? I’m jealous.
i want to know which emulsifiers aresuitable to dissolve perraffin in silicone/water emulsion.as perraffin oils are non polar so kindly do guid me?
Hello,George
How can I make an easiest way to make an emulsifier?
P.S.I want the answer fastest as you can.
Phum
hey phum … would u please explain ur question more … sorry for that but i didn’t get the question to answer u !
Thanks so much.
I want to ask one question:
How i can prepare an EC of mineral oil(raw liquid parrafin oil)?I know some emulsifiers can use for it but with high using level(about 8%-10 %).I want to use a suitable emusifier with lower usage than it.
regards
Abbasi
hey all …
I want to prepare the following formula:
1- 40 g vaseline
2- 40 g water
3- 8 g emulsifier ( i shose Span 60″sorbitan monostearate, HLB = 4.7 and tween 60, hlb = 14.9): 7 g span 60 + 1 g tween 60)
i heated to 70 for the oily phase and 73 for the water phase ..
i mixed with a large stirring around 3000 RPM…
the emulsion created is great .. but it lack the stability in 50 C
CAN ANYONE OF U EXPLAIN !!! alghough i balanced the HLB !!
Hi George,
By the looks of it you are trying to create a w/o formulation. These are very tricky formulations to produce with only ethoxylated emulsifiers. Typically, waxes are added to the oil phase to help stbailize these types of emulsions and homogenization is a must. You may want to adjust your oil phase by adding oils with higher required HLBs and try making a o/w emulsion before attempting a w/o with this method.
hi Kelly .. .first i would like to thank u for this quick response
i know that it is better to put some waxes… but i felt that the cream is thick enough due to the large amount of SPAN 60 WAX …
still i don’t want to do O/W cream.. inversely, i’m insisting on W/O creams… if u can help me in this .. because till now none of my formulas was stable at 50 Centigrate for more than 48 hours …( the oily phase begine to separate !!!! )
thanks a lot in advance kelly
Hi George
You are probably going to have to do some research on stabilizing these types of formulas and other ingredients you can use. Good luck with your formulation. -Kelly
My own view is that making successful emulsions is more of an art than a science. My first emulsion, looking back on it, was actually a butter: it contained 25% lipids, of which 15% was shea. It had a salmon colour because of the green tea extract in it. I thought it was a failure, but got demands to make more from test customers who really loved it. More lately I’ve been more into using desert plant bioactives.
How to test the stability of emulsion
Saravanan – see our blog post about stability testing.
HLB value is a usefull tool but chances of product unsafety…
i want understand but i cant ,some one tell me?
Muhammad,
Your question is too vague to answer.
1) Simple mixing with an impeller blade is all that is need to perform the testing.
2) As mentioned above, there is no method for calculating the quantity of surfactants needed. You must determine the quantity experimentally.
3) In general, you slowly add the expected internal phase to the expected external phase. I do not have a formal procedure to share.
4) In general, the external phase should account for >= 26% of the total composition for traditional emulsions based on geometrical consideration of hexagonally packed spheres.
Dear kelly, I just want to know the process of how to make different w/o and o/w emulsions of organic solvents like toluene, hexane, benzene, cyclo hexane etc.. but my problem is that 1) how to set up apparatus for emulsions preparation?
2) how to calculate required qty of surfactant ?
3) what will be mode of addition of compounds ie water phase first or oil phase first….pls give me experimental procdure if possible. 4) I want some std qties for w/o and o/w emulsions of organic solvents as oil phase?
expecting kind reply
Dear Jagat,
You must experimentally determine you required HLB as mentioned about by observing stability with the oil phase and various surfactant combinations to achieved different HLB values. We cannot help until you have done this.
sir good morning
i am taking 35% oil and formulating by taking tween 80 and span 80..i am geting the emulsification aftera week its geting separated . so kindly guide me to sucess my project
sir good morning
sir i have read your all suggestion,its very impressive. sir actually iam taking 40% essential oil and rest is water and excipient.so please guide me to formulate the cream. hope i wil get some detail idea.yours faithfully
@Jagat – I would suggest you post your question to the cosmetic science forum to see if someone there can answer it for you.
sir please help me to my above question
@Jagat – thank you for your questions. Unfortunately, we do not have the protocol or information you seek.
Hi Alicia,
I would use glyceryl stearate, lecithin can have some draw backs with stability my opinion. 7% emulsifiers seems like a high starting point even for your large oil phase. I would place range of emulsifier levels on stability to determine an optimum level. -Kelly
So I’m thinking to do a blend of 40/60 stearic acid and glyceryl stearate:
40% x HLB 15 = 6
60% x HLB 4 = 2.4 = total 8.4 to match my recipe’s HLB requirement (total HLB of all the ingredients in my oil phase)
I saw a rough ratio of 7:1 (oil phase: emulsifier) recommended somewhere in the archives here.. which would mean I require approx 7% total emulsifiers as my oil phase makes up 49% of the total formulation
Would you please confirm am I on the right track with these calcs?
Thank you Kelly for your response, much appreciated!
I am using stearic acid and/ or stearyl alcohol for the high HLB component. From a formulator’s point of view would you recommend glyceryl stearate OR hydrogenated lecithin for the lower value surfactant?
trying to go “nature-identical” as much as possible with the products..but saying that would very much like to get the texture beautiful and stable!
Hi Alicia,
You are correct, you would need a combination of low and high HLB surfactants to emulsify using the HLB system. Or you can try creating soap based emulsion by neutralizing the stearic acid with a base like triethanolamine. -Kelly
I’m just learning about the HLB system and have been trying to perfect the texture of a cream. It has equal proportion of water to oil, has a little grittiness and just a small amount of water separating out. Have done all calculations and come to a total required HLB of 8.36…
And now to select the emulsification system. Would you mind clarifying how I would achieve this with using what I have access to: Stearic acid and stearyl alcohol, both with HLB around 15? Do I need to combine with a low HLB value emulsifier like lecithin (4)? Thanks for your advice!
sir would you like to give me the protocol if u have , how to proceed further for the determination of hlb of some essential oils. if u have some research article then plz send me some of them so that i can proceed further with u r guidance.
regards jagat jyoti sahu
waiting for u r reply
Jagat,
You would run accelerated stability testing with varying levels of emulsifier while holding the oil phase the same.
how we can determine it by experimentally
what is the protocol to determine the level of emulsifier
Jagat,
As noted above, the appropriate level of emulsifier will be determined experimentally.
ok but i want to know the percentage of emulsifier to be used
Hello Jagat,
You will need to experimentally determine the required HLB for your oil. You create emulsions with a combination of high and low HLB emulsifier at varied ratios but the same total concentration to test different HLBs. The required HLB is then taken from the emulsion that remains most stable.
Hi Kelly, yes, i understand what you meant.
Just wonder how to interpret/decide which emulsion remains the most stable? I have set the surfactant to be 3% (parenteral formulation).
Then, all the resulting emulsion seems to be the same. Separation of oil and water has taken place. The oil will immediately float back to above after i shaken the emulsion (although the oil did dispersed into the water when i shaked the emulsion at 1st). However, i do see droplets of oil. They do not aggregate to form a bigger droplets. Should i just proceed with other surfactant? Because the same situation has taken place for the 3rd kind of surfactant’s mixture. Thanks for the advice. =)
i want to know how to calculate the hlb value of cetronella oil.but first point is selection of surfactant.but how we wil select surfactant. we have oil percentage around 83 and water the rest. so kindly tel me on what basis i wil select the surfactant blend
Hi Nancy,
There are no rules on how much emulsifier you need , a good starting point is 2%. Placing various levels on accelerated stability testing can help you to select the optimum level for a particular oil phase.
Hi again Kelly, and thank you one more time
Just like you said i couldent find many.
Id like to aske you if there is any rules in how much emulusifer i should use.
Thanks again!
Nancy
Hi Nancy,
There aren’t many published values for W/O required HLBs, this maybe due to the reason that most cosmetic formulators favor O/W due to cost, ease of stabilization, etc. You may be able to find some if you search for a specific oil and it’s required HLB in W/O systems. Hope this helps!
Thank you for your answer.I do not know what Bancroft rule is but i will look it up.I wonder if you know a site with the HLB value of o/w and w/o emulsions.
Hi Nancy,
That’s a great question! The HLB for oils in O/W vs. W/O is different. Low HLB emulsifiers are used to create W/O formulations, and following the Bancroft Rule the phase in while the emulsifier is most soluble constitutes the continuous phase. So is the emulsifier HLB is low, it would be matched to an oil phase with a low required HLB. For example in O/W mineral has a required HLB around 10 and for W/O it is closer to 5.
hello i am making a project about HLB and i would like to know the hlb value of oils is the same for o/w and w/o emulsions..
Hello Jagat,
You need a required HLB for oils. Required HLB is not calculated but determined experimentally by using a range of emulsifiers with differing HLB values.
please tel me how to calculate the hlb value of volatile oil like geranium oil .
Please guide us , We want to make silicone emulsion shinning polish
for vegetable base oil phase which PEG free emulsifier is best
percentage is about 35 to 40.
Bill,
The HLB system is still a great tool for the formulator and one the I use frequently. The beauty is in the ease with which it can be used. As a big enthusiast of cosmetic science, it’s an honor to hear from you! Thanks so much, Kelly
Glyceryl stearate SE contains a small amount of a monovalent soap such as potassium or sodium stearate.
What is the defferrence between glyceryl monosterate
and glyceryl monostearate self emulsifyig
I want to make water in oil formulation
how can we calculate the HLB for w/o
Kelly Dobos,
Dennis’ comments are a bit amusing in one sense of the word because slide rules were still in use then. Yes, we recognized some of the faults of the system and these were outlined in my thesis for a Master’s Degree in 1955 which, of course, was not published.
It was my unimaginable pleasure to wander through a current emulsion innovation lab at the Croda plant a year or so ago and the advances on all sides was amazing beyond belief. Of course, the truly amazing thing is that the basic premise is still being used and taught so long after its development. Doubly impressive since my retirement happened thirty-one years ago.
Cheers, and may you have as much fun as has been my good fortune in life – and without scads of money.
Bill (HLB) Griffin
I know what I’m going to say here is provocative and sacrilegious, but this whole system seems somewhat antiquated and akin to the slide rule. I think modern formulation requires more flexibility and has available to it more effective tools. Using DOE and polymeric emulsifiers we can create better products faster and discover more unexpected combinations than using these HLB calculations, which don’t account for formula aesthetics or product perception. Even using this system it’s still an iterative process to achieve the look and feel of the product you want.
Certainly, you make an excellent point. There are more rigorous ways of making an emulsion. But this kind of background information is still useful in concept and the method (while antiquated) can still be used effectively.
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