Hydrophilic-lipophilic balance as the main criterion for selecting an emulsifier

Nowadays, the cosmetic market is overflowing with a variety of components, including various emulsifiers. However, such a variety only complicates the choice for beginning cream makers. Which emulsifier or mixture of emulsifiers should be selected to obtain a stable emulsion with the desired properties? What should you pay attention to? Let's figure it out together, relying on basic knowledge of cosmetic chemistry.

What is the hydrophilic-lipophilic balance

Let's note at the very beginning that a cosmetic emulsifier is, by its nature, a surfactant. And each surfactant (surfactant) has a double (diphilic) structure: a hydrophilic* part (also called the "head") and a hydrophobic* part (called the "tail"). Because of this structure, the emulsifier molecule in a water and oil environment tries to turn its hydrophilic part toward the water, and its hydrophobic (i.e. lipophilic) part toward the oil. Thus, the system is stabilized and does not separate, but only if the oil and emulsifier are compatible. That is, they have the same HLB values.

*hydrophilic - that is, soluble in water
*hydrophobic - that is, does not dissolve in water and the synonym for "hydrophobic" is the word lipophilic, that is, soluble in oil

It is the ratio of the hydrophilic part of the molecule to the lipophilic that is called the hydrophilic-lipophilic balance (HLB). This balance is important for understanding the distribution of substances between aqueous and lipid environments, which can affect their physicochemical properties and interactions.

HLB numbers for all known surfactants are on a scale from 0 to 40. This indicator allows you to predict whether the molecule as a whole has a hydrophilic or lipophilic character. The balance between the lipophilic and hydrophilic properties of a surfactant directly affects its solubility or dispersion in water. Thus, the HLB value of various surfactants can be determined by their behavior in water.

No dispersion	HLB = 1-4
Poor dispersion	HLB = 3-6
Unstable milky dispersion	HLB = 6-8
Stable milky dispersion	HLB = 8-10
Transparent opalescent dispersion	HLB = 10-13
Transparent solution	HLB >13

Based on this, the scale of values ​​from 0 to 20 inclusive can be divided into the following groups of surfactants.

Calculation of the hydrophilic-lipophilic balance

Having dealt with the theoretical definition of HLB, we are interested in the following question: how to use it when selecting an emulsifier? And for this, there is a simple rule: the HLB value of the emulsifier should be equal to the HLB value of the oil phase. Therefore, first, we will determine the required HLB of the oil phase and here you will need to take a calculator and think a little.

Oil Phase Required HLB: What It Is and How to Calculate It

If an emulsifier with a certain HLB value stabilizes an emulsion with a certain type of oil, then another emulsifier with the same HLB value will generally have the same emulsifying effect. Thus, each type of oil requires an emulsifier system with a certain HLB value, and this value constitutes the required GBL of the oil phase. The table below shows the required HLB values ​​for some common oils, emollients, and fatty alcohols.\

Fat phase component	Required HLB value
Almond oil	6
Apricot kernel oil	7
Avocado oil	7
Babassu oil	8
Grape seed oil	7
Castor oil	14
Hemp seed oil	7
Cyclomethicone	7,5
Coconut oil	8
Candelilla wax	14,5
Dimethicone	5
Carnauba wax	12
Rosehip oil	7
Jojoba oil	6,5
Macadamia oil	7
Mango seed oil	8
Palm oil	10
Olive oil	7
Rice bran oil	7
Sesame oil	7
Shea butter	8
Soybean oil	7
Sunflower oil	7
Cocoa butter	6
Rose wax	12
Lanolin	10

If the oil phase consists of one oil, then the calculations are quite simple: we simply take the HLB value of our oil from the table and take it as the required HLB value of the entire fat phase.

However, we usually use not one, but several oils to give the cream special properties. In this case, the HLB of the oil phase will be equal to the sum of the HLB contributions of each oil proportionally to its percentage. Let's look at an example.

Let's assume that our oil phase consists of:

• olive oil - 5%
• coconut oil - 1%
• avocado oil - 3%
• carnauba wax - 1%.

The total proportion of oils in our oil phase = 10%. To calculate the required HLB, we must calculate the composition of our oil phase in percentage. Therefore, we can say that 10% of our formula = 100%. Recalculating according to the proportion, we get:

• olive oil - 50%
• coconut oil - 10%
• avocado oil - 30%
• carnauba wax - 10%.

Taking the HLB values ​​of each component from the table, we can calculate the total HLB of the oil phase using the formula:

Oil HLB * (% of its addition/100) + Oil HLB * (% of its addition/100) + Oil HLB * (% of its addition/100) = the HLB of the oil phase we need

Below you can see an example of calculating the HLB of the oil phase, which we took as an example, where 7 is the HLB of olive oil, and 0.5 is 50% olive oil in the oil phase/100, and then we write down each component according to this scheme and find the value we need:

7*0.5+8*0.1+7*0.3+12*0.1=7.6

As a result of the calculation, we got the HLB of the oil phase of 7.6.

Selecting an emulsifier by the HLB index

If your head is not spinning yet, let's continue. Knowing the HLB of the oil phase, we use the already known rule: to create a stable emulsion, the HLB value of the emulsifier must be equal to the HLB value of the oil phase. The table below shows the HLB indices of common emulsifiers. This information for your specific emulsifier can be found in the process documentation or the emulsifier description on the supplier's website.

Emulsifier	HLB
Ecomuls 2 in 1	3
Emulpharma 1000	9,5
Sorbitan Olivate	4,7
Emulpharma ECOTECH	8
Arlacel 2121	6
MONTANOV 202	8,3
MONTANOV 68	9,3
Olivem 1000	9
Planta M	12
Plantasens HE20	9,5
Sisterna SP-70C	15
Calcium Stearoyl Lactylate	5.1
Glyceryl Stearate	3,8
Glyceryl Stearate, PEG-100 Stearate	11
Ceteareth-20	15.2
Cetearyl Glucoside	11
Sorbitan Oleate	4,3
Glycol Stearate	2,9
Polysorbate 80	15
Glyceryl Laurate	5,2
Polysorbate 60	14,9
Glycol Distearate	1
Polysorbate 20	16,7
Sorbitan Trioleate	1,8

Of course, you can take 1 universal mixed emulsifier, such as Olivem 1000 or Montanov 68. However, sometimes you should not rush to choose 1 emulsifier with an HLB value of 7-8. After all, it has been experimentally established that a set of several emulsifiers: one with a lower HLB, and another with a higher HLB work better than an emulsifier with an intermediate HLB value. Therefore, give preference to a mixture of emulsifiers.

Now we need to select the proportions of emulsifiers so that the final HLB is equal to the HLB of the fat phase that we have already calculated - 7.6. We select two emulsifiers, let them be: Sorbitan Olivate (HLB 4.7) and Emulpharma 1000 (HLB 9.5). Taking Sorbitan Olivate as the proportion x, we will make an equation:

Where 4.7 and 9.5 are the HLB values ​​of the emulsifiers themselves, and 7.6 is the value that we need to obtain. Having solved this equation (see the example above), we get the value of "x", it is equal to 0.396. For us, this means that we need to take 39.6% Sorbitan Olivate and the remaining 60.4% will be Emulpharma 1000. Before we calculate the percentages of emulsifiers using the formula, we must decide how much emulsifier we want to use in our formula. Usually, we start with a smaller percentage and test, gradually increasing it. For our example, let's take the total content of emulsifiers in the formula - 5%. Recalculating, we get:

• 5% * 0.396 = 1.98
• 5% * 0.604 = 3.02

Rounding, we have the following final percentage ratios of emulsifiers in the formula: 2% Sorbitan Olivate, 3% Emulpharma 1000. And now we can write down the formula in full, test it for stability and make adjustments to the percentage of added emulsifiers, if necessary. And do not forget about the use of fatty alcohols in the oil phase, so that your emulsion is thick, but at the same time light and delicate. We wrote about this in the article "Fatty alcohols in cosmetics".

HLB is a useful criterion at the stage of selecting an emulsifier, but it does not indicate how much emulsifier exactly should be taken from the total mass of the emulsion. Therefore, it is necessary to focus on the permissible input limits recommended by manufacturers, and also strive for the minimum required amount that ensures the stability of the cream. The hydrophilic-lipophilic balance is important, but not the only criterion that determines the stability of the cream. When selecting an emulsifier, you should also take into account the working pH range of the emulsifier and the desired pH of the finished emulsion. As well as the presence of specific components in the formula that may be incompatible with the selected emulsifier. We wish you success in creating your own formulas and do not forget that on the BEURRE Cosmetic Kitchen channel we regularly share video tutorials on creating natural cosmetics with your own hands at home.