Process: Emulsions
Oil in Water vs. Water in Oil
There are two types of emulsions: oil in water (o/w) AND water in oil (w/o).
The chief difference in oil in water vs. water in oil emulsions is the type of emulsifying agent. When you are making an oil in water emulsion, you must force the oil into the water. When you are making a water in oil emulsion, you must force the water into the oil. When you make an oil in water emulsion, the oil is made into small droplets which is spread throughout the water. In this case, you would add the oil to the water. The reverse is true for water in oil emulsions.
The function of the emulsifying agent is to spread the droplets, and to ensure the droplets stay spread out. The type of emulsion is controlled by the HLB value (hydrophilic lipophyllic balance) of the emulsifying agent. This is basically the ratio of the weight of the molecule which is hydrophilic (water loving) to the weight that is lipophyllic (oil loving). Although each fixed oil has a specific HLB requirement for it to emulsify, the better systems provide adequate emulsifying activity.
Below is a list of HLB values and their corresponding applications:
HLB VALUES |
APPLICATION |
1-3 |
Antifoaming agents |
3-6 |
Emulsifying agents (w/o emulsions) |
7-9 |
Wetting agents |
8-18 |
Emulsifying agents (o/w emulsions) |
13-16 |
Detergents |
16-18 |
Solubilizing agents |
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The following is a list of commonly used emulsifying agents, both synthetic and natural.
| Commercial NameChemical Name |
HLB Value |
| AcaciaAcacia |
12.0 |
| Glyceryl monostearateGlyceryl monostearate |
3.8 |
| Methocel 15 cpsMethylcellulose |
10.5 |
| Parmagel BGelatin |
9.8 |
| Liquid SoapPotassium soap |
20.0 |
| Cold Process SoapSodium soap |
18.0 |
| TragacanthTragacanth |
13.2 |
| XanthanXanthan |
12.5 |
| Dispersing Sunflower OilSunflower Glycerides PEG-10 |
7.5 |
The Pros & Cons of Emulsion Types
W/O emulsions have a similar structure to the skin and are very skin compatible. They tend to be creams. Their chief disadvantage is that they break and soak in slowly. They may also have a slightly greasy feel. The greasiness can be alleviated, to some extent, by using a low molecular chain oil, such as fractionated coconut or a liquid wax, such as jojoba or isopropyl myristate. Fragrances are readily apparent, but can dissipate quickly. O/W emulsions break easily and have a better skin feel. One of their chief disadvantages is their runniness. They usually require thickening agents. They also have fewer problems with rancidity of the fixed oils because the fixed oils are better protected from oxidation than W/O emulsions. Fragrances are better held in O/W emulsions, though they may seem faint before applying to the skin. If you've made it this far through these pages, congratulations! We applaude your interest in making lotions properly and encourage you to experiment and be creative. Niche markets are everywhere, and you may become the next great lotion entrepeneur. For more information, please read our article on HLB (hydrophilic-lipophilic balance).
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